Chapter 21 biochemistry

Dr. Hashim Ali
Post-Doc Uppsala University, Sweden.
PhD Computational Biology, KTH, Stockholm, Sweden.
Chapter 21 - Biochemistry
Federal Board of Intermediate and Secondary
Education (FBISE)

• Explain the basis of classification and structure-functional relationship of carbohydrates.
• Explain the role of various carbohydrates in health and diseases.
• Identify the nutritional importance and their role as energy storage.
• Explain the basis of classification and structural-functional relationship of proteins.
• Describe the role of various proteins in maintaining body function and their nutritional importance.
• Describe the role of enzyme as biocatalyst and relate this role to various functions such as digestion of
food.
• Identify factors that affect enzyme activity such as effect of temperature and pH.
• Explain the role of inhibitors of enzyme catalyzed reactions.
• Describe the basis of classification and structure-function relationship of lipids.
• Identify the nutritional and biological importance of lipids.
• Identify the structural components of DNA and RNA.
• Recognize the structural differences between DNA polymer (double strand) and RNA (single strand).
• Relate DNA sequence to its function as storage of genetic information.
• Relate RNA sequence (transcript) to its role in transfer of information to protein (translation).
• Identify the sources of minerals such as Iron, Calcium, Phosphorus and Zinc.
After completing this lesson, you will be able to

Chapter Overview - Sections
• Introduction to Biochemistry
• Carbohydrates
• Proteins
• Enzymes
• Lipids
• Nucleic acids
• Minerals of biological significance
Chapter Overview - Sections

Dr. Hashim Ali
21.0 – Introduction to Biochemistry
Education (FBISE)
Chemistry F.Sc
II

• As the name indicates, biochemistry is a hybrid science.
o Biology is the science of living organisms.
o Chemistry is the science if atoms and molecules.
• So biochemistry is the science of the atoms and molecules in living organisms.
• Biochemistry is the branch of science concerned with studying the various
molecules that occur in living cells and organisms, with their chemical reactions.
• Biochemistry is concerned with the complete spectrum of all forms of life, from
relatively simple viruses and bacteria to complex human beings.
• It attempts to describe in molecular terms the structures, mechanisms and
chemical processes shared by all organisms.
• Living organisms should be able to
o transform matter and energy into different forms,
o respond to changes in their environment, and
o show growth and reproduction.
21.0.1 - Introduction - Biochemistry

• There's an old saying, "You are what you eat." In some senses, this is literally true! When we eat food, we take in the large biological
molecules found in the food, including carbohydrates, proteins, lipids (such as fats), and nucleic acids (such as DNA), and use them to
power our cells and build our bodies.
• Dive into the different types of macromolecules, what they are made up of, and how they are built up and broken down.
• Think back to what you ate for lunch. Did any of your lunch items have a “Nutrition Facts” label on the back of them? If so, and if you had a
look at the food's protein, carbohydrate, or fat content, you may already be familiar with several types of large biological molecules we’ll
discuss here. If you’re wondering what something as weird-sounding as a “large biological molecule” is doing in your food, the answer is
that it’s providing you with the building blocks you need to maintain your body – because your body is also made of large biological
molecules!
• Just as you can be thought of as an assortment of atoms or a walking, talking bag of water, you can also be viewed as a collection of four
major types of large biological molecules: carbohydrates (such as sugars), lipids (such as fats), proteins, and nucleic acids (such as DNA and
RNA).
o That’s not to say that these are the only molecules in your body, but rather, that your most important large molecules can be divided into these
groups. Together, the four groups of large biological molecules make up the majority of the dry weight of a cell. (Water, a small molecule, makes up
the majority of the wet weight).
• Large biological molecules perform a wide range of jobs in an organism.
o Some carbohydrates store fuel for future energy needs, and some lipids are key structural components of cell membranes.
o Nucleic acids store and transfer hereditary information, much of which provides instructions for making proteins.
o Proteins themselves have perhaps the broadest range of functions: some provide structural support, but many are like little machines that carry out
specific jobs in a cell, such as catalyzing metabolic reactions or receiving and transmitting signals.
• We’ll look in greater detail at carbohydrates, lipids, nucleic acids, and proteins. Here, we’ll look a bit more at the key chemical reactions that
build up and break down these molecules.
21.0.2 - Introduction - Macromolecules

• Most large biological molecules are polymers, long chains made up of repeating molecular
subunits, or building blocks, called monomers.
o If you think of a monomer as being like a bead, then you can think of a polymer as being like a
necklace, a series of beads strung together.
• Carbohydrates, nucleic acids, and proteins are often found as long polymers in nature.
o Because of their polymeric nature and their large (sometimes huge!) size, they are classified
as macromolecules, big (macro-) molecules made through the joining of smaller subunits.
o Lipids are not usually polymers and are smaller than the other three, so they are not considered
macromolecules by some sources. However, many other sources use the term “macromolecule”
more loosely, as a general name for the four types of large biological molecules.
o This is just a naming difference, so don’t get too hung up on it.
o Just remember that lipids are one of the four main types of large biological molecules, but that they
don’t generally form polymers.
21.0.3 - Introduction – Monomers and polymers

• How do you build polymers from monomers?
• Large biological molecules often assemble via dehydration synthesis reactions, in which one monomer forms a covalent bond to another
monomer (or growing chain of monomers), releasing a water molecule in the process.
• You can remember what happens by the name of the reaction: dehydration, for the loss of the water molecule, and synthesis, for the
formation of a new bond.
• In this dehydration synthesis reaction, two molecules of the sugar glucose (monomers) combine to form a single molecule of the sugar
maltose.
o One of the glucose molecules loses an H, the other loses an OH group, and a water molecule is released as a new covalent bond forms between the two
glucose molecules.
o As additional monomers join by the same process, the chain can get longer and longer and form a polymer.
• Even though polymers are made out repeating monomer units, there is lots of room for variety in their shape and composition.
• Carbohydrates, nucleic acids, and proteins can all contain multiple different types of monomers, and their composition and sequence is
important to their function.
• For instance, there are four types of nucleotide monomers in your DNA, as well as twenty types of amino acid monomers commonly found
in the proteins of your body.
• Even a single type of monomer may form different polymers with different properties.
o For example, starch, glycogen, and cellulose are all carbohydrates made up of glucose monomers, but they have different bonding and branching
patterns.
21.0.4.1 - Introduction – Key chemical reactions – Dehydration
synthesis

• How do polymers turn back into monomers (for instance, when the body needs to recycle one molecule to build a different one)?
• Polymers are broken down into monomers via hydrolysis reactions, in which a bond is broken, or lysed, by addition of a water molecule.
• During a hydrolysis reaction, a molecule composed of multiple subunits is split in two: one of the new molecules gains a hydrogen atom,
while the other gains a hydroxyl (-OH) group, both of which are donated by water.
• This is the reverse of a dehydration synthesis reaction, and it releases a monomer that can be used in building a new polymer.
• For example, in this hydrolysis reaction, a water molecule splits maltose to release two glucose monomers. This reaction is the reverse of the
dehydration synthesis reaction shown earlier.
• Dehydration synthesis reactions build molecules up and generally require energy, while hydrolysis reactions break molecules down and
generally release energy.
• Carbohydrates, proteins, and nucleic acids are built up and broken down via these types of reactions, although the monomers involved are
different in each case.
• In a cell, nucleic acids actually aren't polymerized via dehydration synthesis; we’ll examine how they're assembled in the section on nucleic
acids. Dehydration synthesis reactions are also involved in the assembly of certain types of lipids, even though the lipids are not polymers.
• In the body, enzymes catalyze, or speed up, both the dehydration synthesis and hydrolysis reactions.
• Enzymes involved in breaking bonds are often given names that end with -ase: for instance, the maltase enzyme breaks down maltose,
lipases break down lipids, and peptidases break down proteins (also known as polypeptides, as we’ll see in the article on proteins).
• As food travels through your digestive system – in fact, from the moment it hits your saliva – it is being worked over by enzymes like these.
• The enzymes break down large biological molecules, releasing the smaller building blocks that can be readily absorbed and used by the
body.
21.0.4.2 - Introduction – Key chemical reactions – Hydrolysis

• Here is a good story and those who wear contact lens can relate!
o As a kid (and even now!), I wore glasses and desperately wanted a pair of contact lenses.
o I only happened to get one pair of contact lenses, when I was a teenager.
o I was instructed that you had to take them off before sleeping and put them in a solution called “enzymatic
cleaner”, which would clean them. Then, in the morning wash them with clean water and put them back in
your eyes.
o Unfortunately, the next day, while cleaning them, I lost one of the transparent lenses in the sink. After that,
I have stuck to glasses for good.
o I didn’t know exactly what “enzymatic cleaner” meant, but I did learn that if you forgot you’d added it and
accidentally put your contacts in your eyes without washing them, you were going to have burning eyes for
a good fifteen minutes.
o As I would later learn, all that “enzymatic” meant was that the cleaner contained one or more enzymes,
proteins that catalyzed particular chemical reactions – in this case, reactions that broke down the film of
eye goo that accumulated on my contacts after use. (Presumably, the reason it stung when I got it in my
eyes was that the enzymes would also happily break down eye goo in an intact eye.)
• In this chapter, we’ll look in greater depth at what an enzyme is, how it catalyzes a particular
chemical reaction and what are the factors affecting the enzyme activity.
21.0.5 - Introduction – Enzymes

21.0 - Introduction to Biochemistry
Dr. Hashim Ali
Education (FBISE)
Chemistry F.Sc
II

Dr. Hashim Ali
21.1 – Carbohydrates
Education (FBISE)
Chemistry F.Sc
II

• Carbohydrates are called carbohydrates because they contain carbon,
oxygen and hydrogen, and these are “generally” in the proportion to form
water with the general formula Cn(H2O)n.
o Note the word generally.
o Because all organic compounds containing hydrogen and oxygen in the proportion
of 2:1 are not carbohydrates. For example formaldehyde (HCHO), acetic acid
(CH3COOH) and lactic acid (CH3CHOHCOOH).
o More importantly, some carbohydrates like Rhaminose (C6H12O5) do not have the
same ratio of hydrogen to oxygen as in H2O but is a carbohydrate.
• Carbohydrates are poly-hydroxy compounds of aldehydes or ketones.
21.1.1 – Carbohydrates - Introduction

• Carbohydrates or saccharides are the most abundant of the four types of macromolecules.
• These are sugars or starches.
• They have several roles in living organisms, including energy transportation, as well as being
structural components of plants and arthropods.
• Carbohydrate derivatives are actively involved in
o fertilization,
o immune systems,
o development of disease,
o blood clotting and
o growth.
• Most organic matter on earth is made up of carbohydrates because they are involved in many
aspects of life, including:
o Energy stores, fuels, and metabolic intermediaries.
o Ribose and deoxyribose sugars are part of the structural framework of RNA and DNA.
o The cell walls of bacteria are mainly made up of polysaccharides (types of carbohydrates).
o Cellulose (a type of carbohydrate) makes up most of plant cell wall.
o Carbohydrates are linked to many proteins and lipids (fats) where they are vitally involved in cell
interactions.
21.1.2 – Carbohydrates - Roles in living organisms

• Carbohydrates are classified into three types.
o Monosaccharides
o Disaccharides
o Polysaccharides
21.1.3 – Carbohydrates - Classification

• The carbohydrates which do not hydrolyze to
simpler units are called monosaccharides.
• This is the smallest possible sugar unit.
• Examples are glucose, galactose and fructose.
o When we talk about blood sugar, we refer to glucose
in the blood which is also a major source of energy
for the cells.
o Glucose is naturally present in honey and corns.
o In human nutrition, galactose can be found most
readily in milk and dairy products.
o Fructose is mostly found in vegetables and fruits
(grapes).
• When monosaccharides merge together in linked
groups, they are called polysaccharides.
• Each monosaccharide molecule is identified by the
number of carbons present.
o However, hexoses (6 carbons) are by far the most
prevalent.
21.1.3.1 – Carbohydrates - Classification - Monosaccharides
Glucose (open
chain form)
⍺-D-Glucose
β-D-Glucose
Fructose (open
chain form)
Fructose (cyclic
form)

• Two monosaccharide molecules are bonded together to form disaccharides.
• Disaccharides are polysaccharides:
o Poly specifies any number higher than one.
o Di specifies exactly two.
• Examples of disaccharides include lactose, maltose, and sucrose.
o Lactose, a sugar composed of galactose and glucose, is found in milk.
o Sucrose occurs in sugarcane, sugar beet, mango, pineapple, almond and apricot.
21.1.3.2 – Carbohydrates - Classification - Disaccharides
glucose glucose maltose
glucosegalactose lactose
sucroseglucose fructose

• The carbohydrates producing large number of
macro-molecules on hydrolysis are called
polysaccharides.
• Starch and cellulose are examples of
polysaccharides.
• It is a chain of two or more monosaccharides.
• The chain may be branched (molecule is like a tree
with branches and twigs) or unbranched
(molecule is a straight line with no twigs).
• Polysaccharide molecule chains may be made up
of hundreds or thousands of monosaccharides.
• Polysaccharides are polymers, where a simple
compound is a monomer while a complex
compound made up of two or more monomers is a
polymer.
• A new system for classifying carbohydrates is the
glycemic index, which ranks foods on how they
affect blood sugar level by measuring how much
the blood sugar increases after one eats.
21.1.3.3 – Carbohydrates - Classification - Polysaccharides
Carbohydrates
Monosaccharides Disaccharides Polysaccharides
Glucose Sucrose Starch
Galactose Maltose Cellulose
Fructose Lactose Glycogen
Ribose
Glyceraldehyde
glucose
starch
cellulose

• They serve as the main energy source of cells so that proteins (alternate
energy) can concentrate on building, repairing and maintenance of
body tissues instead of being used up as an energy source.
• For fat to be metabolized properly, carbohydrates must be present.
o If there are not enough carbohydrates, a large amount of fats are used for
energy.
o The body is not able to handle this large amount so quickly, so it
accumulates ketone bodies which makes the body acidic. This causes a
condition called ketosis.
• Carbohydrates are necessary for the regulation of nerve tissue and is
the only source of energy for the brain.
• Certain types of carbohydrates support the growth of healthy bacteria in
the intestine for digestion.
• Some carbohydrates are high in fiber, which helps prevent constipation
and lowers the risk for certain diseases such as cancer, heart disease
and diabetes.
• Polysaccharides act as food stores in plants in the form of starch, or in
humans and other animals in the form of glycogen.
• Polysaccharides also have structural roles in the plant cell wall in the
form of cellulose or pectin, and the tough outer skeleton of insects in
the form of chitin.
• Three major functions of polysaccharides are:
o Storage.
o Structural.
o Bacterial defense against immune system.
21.1.4 – Carbohydrates - Functions

• Glycogen is a polysaccharide that human and animals store in the liver and muscles.
• Starches are glucose polymers made up of Amylose (10-20%) and Amylopectin (80-90%).
o Starches are water insoluble, so human and animals digest them by hydrolysis; our bodies have
amylases, which break them down.
o Rich sources of starches for humans are potatoes, rice and wheat.
• Structure of Amylase and Amylopectin.
21.1.4.1 – Carbohydrates - Functions - Storage polysaccharides
amylopectin
amylose

• Cellulose is a type of polysaccharide and is the main structural constituent of plants.
• Wood is mostly made of cellulose, while paper and cotton are almost pure cellulose.
• Chitin, a polysaccharide, is one of the most abundant natural materials in the world.
• Microorganisms such as bacteria and fungi secrete chitinases, which over time can break
down chitin.
• Chitin is the main component of fungi cell walls, the exoskeletons (hard outer shell/skin)
of arthropods, such as crabs, lobsters, ants, beetles and butterflies.
21.1.4.2 – Carbohydrates - Functions – Structural
polysaccharides
cellulose
chitin

• They are found in the bacteria,
especially in bacterial capsules.
• Pathogenic bacteria often produce a
thick layer of mucous like
polysaccharide which protects the
bacteria from the host’s immune
system.
• In other words, if the bacteria were in
a human, that human’s immune
system would less likely attack the
bacteria because the polysaccharide
layer covers its pathogenic properties.
21.1.4.3 – Carbohydrates - Functions – Bacterial polysaccharides

• Scientific research has shown the diverse
functions of carbohydrates in the body
and their importance for good health.
• Bread, pasta, beans, potatoes, bran rice
and cereals are carbohydrate-rich foods.
• Carbohydrates are also a poorer source of
energy per unit mass as compared to
other sources;
o 1 gram of carbohydrate contains
approximately 4 calories (cal).
o 1 gram of protein contains approximately 4
cal.
o 1 gram of fat contains approximately 9 cal.
21.1.5 – Carbohydrates – Nutritional importance

• People eating a diet high in carbohydrates are less
likely to accommodate body fat as compared to
those who follow a low carbohydrate/high fat diet.
• The reasons for this observation are threefold:
o It could be due to the lower energy density of high
carbohydrate diets, as carbohydrates have fewer
calories than fats.
o Fiber-rich foods also tend to be bulky and physically
filling, so fewer calories may be consumed.
o Studies show that carbohydrates, both in the form
of starch and sugars, work quickly to aid satiety and
that those consuming high carbohydrate diets are
therefore less likely to overeat.
• It is evident that diets high in carbohydrate, as
compared with those high in fat, reduce the
likelihood of developing obesity.
• In several studies, high sugar consumers have been
found to be slimmer than low sugar consumers.
21.1.5.1 – Carbohydrates – Nutritional importance – Body weight
regulation

• There is no evidence that sugar consumption is
linked to the development of any type of diabetes.
• However, there is now good evidence that obesity
and physical inactivity increase the likelihood of
developing non-insulin dependent diabetes, which
usually occur in the middle age.
• Weight reduction is usually necessary and is the
primary dietary aim for people with non-insulin
dependent (Type II) diabetes.
• Consuming a wide range of carbohydrate foods is
an acceptable part of the diet of all diabetics, and
the inclusion of low glycaemic index foods is
beneficial as they help to regulate blood glucose
control.
• Most recommendations for the dietary
management of diabetes allow a modest amount of
ordinary sugar as the inclusion of sugar with a meal
has little impact on either blood glucose or insulin
concentrations in people with diabetes.
21.1.5.2 – Carbohydrates – Nutritional importance – Diabetes

• The incidence of tooth decay is influenced by a number of factors.
• These include:
o degree of oral hygiene and plaque removal carried out.
o availability of fluoride.
o type of food eaten.
o frequency of consumption of any fermentable carbohydrate.
o genetic factors.
• Foods containing sugars or starch can be broken down by the
enzymes and bacteria in the mouth to produce acid which attacks
the enamel of the teeth.
• However it is not the amount of sugar or other carbohydrate that
is important but how often they are consumed.
• After an acid challenge, saliva provides a natural repair process
which rebuilds the enamel.
• When carbohydrate-containing foods are consumed too
frequently, or nibbled over time, this natural repair process is
overwhelmed and the risk of tooth decay is increased.
21.1.5.3 – Carbohydrates – Nutritional importance – Dental
health

• There is now substantial evidence that carbohydrates
can improve the performance of athletes.
• During high intensity exercise, carbohydrates are the
main fuel for the muscles.
• By consuming high levels of carbohydrates before,
during and after training or an event, glycogen stores
are kept well stocked.
• These stocks help the athletes to perform for longer
and help their bodies sustain the effort.
• The vital role of physical activity in maintaining health
and fitness in the general population is now recognized.
• There is no doubt that many people would benefit from
increasing their activity level as it helps in the
regulation of body weight.
• It also reduces the risk of developing diseases such as
heart disease and diabetes.
• For those who want to keep fit and active, a well-
balanced high-carbohydrate diet is recommended.
21.1.5.4 – Carbohydrates – Nutritional importance – Getting
active

• What are carbohydrates? Give its general formula.
• Quote one example of each type of carbohydrate.
• Write structural formulae of Glucose and Fructose.
• What do you understand by glycemic index?
• How much calories do 1 gram of carbohydrate have?
• On what factors tooth decay depend?
21.1.6 – Carbohydrates – Quick quiz

21.1 - Carbohydrates
Dr. Hashim Ali
Education (FBISE)
Chemistry F.Sc
II

Dr. Hashim Ali
21.2 – Proteins
Education (FBISE)
Chemistry F.Sc
II

• The molecules which yield amino acids on
complete hydrolysis are called proteins.
• Proteins are probably the most important class of
biochemical molecules, although of course lipids
and carbohydrates are also essential for life.
• Proteins are the basis for the major structural
components of animal and human tissue.
• Proteins are natural polymer molecules consisting
of amino acid units.
• The number of amino acids in proteins may range
from two to several thousand.
• These molecules contain nitrogen, carbon,
hydrogen and oxygen.
• They are the workhorses of the cell, where they
o act as biological catalysts (enzymes),
o form structural parts of organisms,
o participate in cell signal and recognition factors, and
o act as molecules of immunity.
• Proteins can also be a source of fuel.
21.2.0 – Proteins - Introduction
amino acid

• Proteins are classified into three classes.
o Simple proteins.
o Compound or conjugate proteins.
o Derived proteins.
21.2.1 – Proteins - Classification

• These proteins on hydrolysis yield only amino acids or their derivatives.
• Some examples of simple proteins are:
o Albumins.
o Globulins.
o Glutelins.
o Histones.
21.2.1.1 – Proteins – Classification – Simple proteins

• The albumins (formed from Latin: albumen "(egg) white; dried egg white") are
a family of globular proteins, the most common of which are the serum (blood)
albumins.
• Globular proteins (spheroproteins) are spherical ("globe-like") proteins and are
one of the common protein types (the others being fibrous, disordered and
membrane proteins).
• All the proteins of the albumin family are water-soluble, moderately soluble in
concentrated salt solutions, and experience heat denaturation.
• It is precipitated by saturation with ammonium sulfate solution and is found in
both plant and animal tissues.
• Substances containing albumins, such as egg white, are called albuminoids.
• Albumins are found in blood (serumbumin), milk (lactalbumin), egg white
(ovolbumin), lentils (legumelin), kidney beans (phaseolin) and wheat (leucosin).
21.2.1.1.1 – Proteins – Classification – Simple proteins -
Albumins

• The globulins are a family of globular proteins that have higher molecular
weights than albumins and are insoluble in pure water but dissolve in dilute salt
solutions.
• Some globulins are produced in the liver, while others are made by the immune
system.
• The term "globulin" is sometimes used synonymously with "globular protein".
o However, albumins are also globular proteins, but are not globulins.
o All other serum globular proteins are globulins.
• They are precipitated by dilute ammonium sulfate and coagulate by heat.
• They are distributed in both plant and animal tissues.
• Globulins are found in blood (serum globulins), muscle (myosin), potato
(tuberin), hemp (edestin) and lentils (legumin).
21.2.1.1.2 – Proteins – Classification – Simple proteins -
Globulins

• Glutelins are insoluble in water and in dilute basic solutions but soluble in
dilute acids.
• Glutelins are mainly found in grains and cereals.
• They can be extracted from wheat (glutenin) and rice (oryzenin).
21.2.1.1.3 – Proteins – Classification – Simple proteins - Glutelins

• Histones are found in thymus
gland, pancreas and nucleoproteins
(nucleohistone).
• It is highly alkaline, and soluble in
water, salt solutions and dilute
acids.
• It is insoluble in ammonium
hydroxide.
• It yields small amounts of lysine
and arginine.
• They are combined with nucleic
acids within cells.
21.2.1.1.4 – Proteins – Classification – Simple proteins - Histones

• A conjugated protein is a protein that functions in interaction
with other (non-polypeptide) chemical groups (called prosthetic
groups) attached by covalent bonding or weak interactions.
• Nucleoproteins are typical examples of conjugated proteins.
o Found in cytoplasm of cells (ribonucleoprotein), nucleus of
chromosomes (deoxyribonucleoprotein), viruses and
bacteriophages.
o Contains nucleic acids, nitrogen and phosphorus.
o Present in chromosomes and in all living forms as a combination of
protein with either DNA or RNA.
• Mucoprotein are also conjugated proteins.
o Found in saliva (mucin) and egg white (ovomucoid).
o These are proteins combined with amino sugars, sugar acids and
sulfates.
• Glycoprotein are conjugated proteins.
o Found in bone (osseomucoid), tendons (tendomucoid), and
cartilege (chondromucoid).
o These are proteins combined with amino sugars, sugar acids and
sulfates.
o If contain more than 4% hexosamine, then they are mucoproteins;
otherwise glycoprotein.
• Phosphoprotein are conjugated proteins.
o Found in milk (casein) and egg yolk (ovovitellin).
o Phosphoric acid joined in ester linkage to protein.
21.2.1.2 – Proteins – Classification – Conjugated proteins

• Those proteins which are derived from simple and
conjugated proteins, are called derived proteins.
• Proteans are derived proteins that are found in edestan
(elastin) and myosin (myosin).
o Insoluble in water
o Result from short action of acids or enzymes.
• Proteoses are intermediate products of protein
digestion.
o Soluble in water.
o Not coagulated by heat.
o Precipitated by saturated ammonium sulfate.
o Result from partial digestion of protein by pepsin or trypsin.
• Peptones are intermediate products of protein
digestion.
o Same properties as proteases except they can not be salted
out and have less molecular weight than proteases.
• Peptides are also intermediate products of protein
digestion.
o Two or more amino acids joined by a peptide linkage.
o Are hydrolyzed to individual amino acids.
21.2.1.3 – Proteins – Classification – Derived proteins

• The structure of a protein depends
upon the spatial arrangement of
polypeptide chains present in
proteins.
• Since three spatial arrangements
are possible, proteins have the
following structures.
o Primary structure
o Secondary structure
o Tertiary structure
o Quaternary structure
21.2.2 – Proteins – Structure

• The sequence of amino acids in a
peptide chain is called primary
structure.
• Amino acids are linked with one
another through peptide bond.
• The arrangement of these acids is
called primary structure.
21.2.2.1 – Proteins – Structure – Primary structure

• Peptide chains may acquire some
shape or may be present in a zig-
zag manner.
• This coiling or zig-zagging of
polypeptide is called secondary
structure of proteins.
• It is due to H-bond.
21.2.2.2 – Proteins – Structure – Secondary structure

• Twisting or folding of polypeptides
chains represents tertiary
structures of proteins.
21.2.2.3 – Proteins – Structure – Tertiary structure

• Quaternary means four.
• This is the fourth phase in the
creation of a protein.
• Quaternary protein is the
arrangement of multiple folded
protein or coiling protein molecules
in a multi-subunit complex.
• A variety of bonding interactions
including hydrogen bonding, salt
bridges and disulfide bonds hold
the various chains into a particular
geometry.
21.2.2.4 – Proteins – Structure – Quaternary structure

• Proteins are one of the four major groups of macromolecules that are found in all
living organisms.
• These giant molecules carry out many of the vital functions needed by cells.
• Proteins are involved in such processes as food digestion, cell structure,
catalysis, movement, energy manipulation and much more.
• They are complex, huge associations of molecular subunits that appear
impossibly difficult to understand.
• Fortunately, they are all built using the same construction principle.
• As with all macromolecules, proteins are polymers, composed of smaller
subunits – the amino acids – joined together in long chains.
• There are about 20-22 common amino acids found in most proteins.
• All but one of these small molecules has the same common structure but varies
in the nature of one chemical group – termed the “R-group”.
• Amino acids are joined together in long chains called polypeptides.
21.2.3 – Proteins – Characteristics

• Proteins are the workhorses of the cell!
• Proteins play an important role in the formation of protoplasm,
which is an essence of all form of life.
• Nucleoproteins are complex proteins and act as the carrier of
heredity from one generation to the other.
• Enzymes are the biological catalyst and they are also proteins;
without enzymes, life is not possible.
• Hemoglobin is a protein, which acts as a carrier of oxygen.
• Some of the proteins act as hormones (special messenger
molecules produced in endocrine glands) and carry out the
regulatory function of the body, e.g., insulin in pancreas and
human growth hormone in pituitary gland.
• Proteins have great importance in industry, e.g., the industrial
process of tanning of hides is the precipitation of protein by
tannic acid.
• Gelatin is obtained by heating bones, skins and tendons in water,
and is used in bakery goods.
• Casein is another protein used in the manufacture of buttons and
buckets.
• Proteins obtained from the soya bean are used for the
manufacture of plastics.
21.2.4 – Proteins – Importance

• What are proteins? Give its simplest classification.
• Differentiate primary, secondary and tertiary structures of proteins.
• What are polypeptides?
21.2.5 – Proteins – Quick quiz

21.2 - Proteins
Dr. Hashim Ali
Education (FBISE)
Chemistry F.Sc
II

Dr. Hashim Ali
21.3 – Enzymes
Education (FBISE)
Chemistry F.Sc
II

• The word “Enzymes” has originated from Greek with “En” meaning “in” and
“Zyme” meaning “yeast”.
• Enzymes are biocatalysts which alter the speed of metabolic activities in the
living cells.
• Enzymes are complex protein molecules which are quite specific in action and
sensitive to temperature and pH.
• Winnhelm Kuhne (1978) first used the term enzyme.
• There are over 2000 known enzymes, each of which is involved in one specific
chemical reaction.
• Enzymes are substrate-specific.
o The enzyme protease (which breaks peptide bonds in proteins) will not work on starch
(which is broken down by an enzyme amylase).
o Similarly, lipase enzyme acts on lipids and digests them into fatty acids and glycerol.
21.3.0 – Enzymes – Introduction

• A substance that speeds up a chemical reaction—without being a reactant—is called a catalyst.
• The catalysts for biochemical reactions that happen in living organisms are called enzymes. Enzymes are usually
proteins, though some ribonucleic acid (RNA) molecules act as enzymes too.
• Metabolism, the set of biochemical reactions that occur in living organ, is in order to maintain life.
• These processes allow organism to
o grow and reproduce
o maintain their structures and
o respond to their environments.
• Anabolism includes the biochemical reactions in which larger molecules are synthesized while catabolism includes
the biochemical reactions in which larger molecules are broken down.
• Usually energy is released in catabolism and is utilized in anabolism.
• In this way, the biochemical reactions are actually energy transfers.
• Enzymes perform the critical task of lowering a reaction's activation energy—that is, the amount of energy that
must be put in for the reaction to begin.
• Enzymes work by binding to reactant molecules and holding them in such a way that the chemical bond-breaking
and bond-forming processes take place more readily.
• To clarify one important point, enzymes don’t change a reaction’s ∆G value. That is, they don’t change whether a
reaction is energy-releasing or energy-absorbing overall. That's because enzymes don’t affect the free energy of the
reactants or products.
• Instead, enzymes lower the energy of the transition state, an unstable state that products must pass through in
order to become reactants. The transition state is at the top of the energy "hill" in the diagram below.
• During metabolism, chemicals are transformed from one form to the other by enzymes.
• Enzymes are crucial to metabolism because they act as biocatalysts and speed up and regulate metabolic pathways.
• Enzymes are proteins that catalyze (i.e., speed up) biochemical reactions and are not changed during the reaction.
• The molecules at which enzymes act are called substrates, and enzyme converts them into different molecules,
called products.
21.0.5.1 - Introduction – Enzymes – Activation energy

• To catalyze a reaction, an enzyme will grab on (bind) to one or more reactant molecules. These molecules are the
enzyme's substrates.
• In some reactions, one substrate is broken down into multiple products. In others, two substrates come together to create
one larger molecule or to swap pieces. In fact, whatever type of biological reaction you can think of, there is probably an
enzyme to speed it up!
• The part of the enzyme where the substrate binds is called the active site (since that’s where the catalytic “action”
happens).
• When enzyme attaches with a substrate, a temporary enzyme-substrate (ES) complex is formed.
• Enzyme catalyzes the reactions and substrate is transformed into product.
• After it the ES complex breaks and the result is enzyme and product.
• In order to explain the mechanism of enzyme action, a German chemist Hermann Emil Louis Fischer (Emil Fischer) in
1894, proposed lock and key model.
• According to this model, both enzyme and substrate possess specific shapes that fit exactly at one another.
• This model explains enzyme specificity.
• In enzymes that are proteins, the active site gets its properties from the amino acids it's built out of. These amino acids
may have side chains that are large or small, acidic or basic, hydrophilic or hydrophobic.
• The set of amino acids found in the active site, along with their positions in 3D space, give the active site a very specific
size, shape, and chemical behavior. Thanks to these amino acids, an enzyme's active site is uniquely suited to bind to a
particular target—the enzyme's substrate or substrates—and help them undergo a chemical reaction.
• Different types of enzymes have different degrees of specificity, or "pickiness" about which molecules can be used as
substrates. Some enzymes accept only one particular substrate and will not catalyze a reaction even for a very closely
related molecule. Other enzymes can act on a range of target molecules, provided that these target molecules contain the
type of bond or chemical group that the enzyme targets.
21.3.1.1.1 – Enzymes – Role as biocatalysts – Working of enzymes
– The lock and key model
E+S ES complex E + P

• In 1958, an American biologist Daniel Koshland suggested a modification to lock and key model, and proposed induced-fit model.
• According to this model, active site is not a rigid structure but is rather molded into the required shape to perform its function.
• Induced fit model is more acceptable than the lock and key model of enzyme action.
• When an enzyme binds to its substrate, we know it lowers the activation energy of the reaction, allowing it to happen more quickly. But, you
may wonder, what does the enzyme actually do to the substrate to make the activation energy lower?
• The answer depends on the enzyme.
o Some enzymes speed up chemical reactions by bringing two substrates together in the right orientation.
o Others create an environment inside the active site that's favorable to the reaction (for instance, one that's slightly acidic or non-polar).
o The enzyme-substrate complex can also lower activation energy by bending substrate molecules in a way that facilitates bond-breaking, helping to
reach the transition state.
o Finally, some enzymes lower activation energies by taking part in the chemical reaction themselves. That is, active site residues may form temporary
covalent bonds with substrate molecules as part of the reaction process.
• An important word here is "temporary." In all cases, the enzyme will return to its original state at the end of the reaction—it won't stay
bound to the reacting molecules.
• In fact, a hallmark property of enzymes is that they aren't altered by the reactions they catalyze.
• When an enzyme is done catalyzing a reaction, it just releases the product (or products) and is ready for the next cycle of catalysis.
21.3.1.1.2 – Enzymes – Role as biocatalysts – Working of
enzymes – The induced fit model

• Enzymes are very sensitive to the environment in which they work.
• Any factor that can change the chemistry or shape of an enzyme molecule,
can affect its activity.
• Some of the factors that can affect the rate of enzyme action are:
o Temperature
o Substrate concentration
o pH
o Role of inhibitors
21.3.2 – Enzymes – Factors affecting enzyme activity

• Increase in temperature speeds up the rate of enzyme
catalyzed reactions, but only to a point.
• Every enzyme works at its maximum rate at a specific
temperature called as the optimum temperature for
that enzyme.
• When temperature rises to a certain limit, heat adds in
the activation energy and also provides kinetic energy
for the reaction, so reactions are accelerated.
• But when temperature is raised well above the
optimum temperature, heat energy increases the
vibrations of atoms of enzyme and the globular
structure of enzyme is lost.
• This is known as denaturation of enzyme and results in
rapid decrease in rate of enzyme action and may block
the reaction completely.
21.3.2.1 – Enzymes – Factors affecting enzyme activity –
Temperature

• If enzyme molecules are available in a reaction,
increase in substrate concentration increases the
rate of reaction.
• If enzyme concentration is kept constant and
amount of substrate is increased, a point is
reached where any further increase in substrate
does not increasee the rate of reaction any more.
• When the active sites of all enzymes are occupied
(at high substrate concentration), any more
substrate molecules do not find free active site.
• This state is called saturation of active site and
reaction rate does not increase.
21.3.2.2 – Enzymes – Factors affecting enzyme activity –
Substrate concentration

• All enzymes work at their maximum rate at a
narrow range of pH, called as the optimum pH.
• A slight change in this pH causes retardation in
enzyme activity or blocks it completely.
• Every enzyme has its specific optimum pH value.
• For example pepsin (working in stomach) is active
in acidic medium (low pH) while trypsin (working
in small intestine) shows its activity in alkaline
medium (high pH).
• Change in pH can affect the ionization of the
amino acids at the active site.
21.3.2.3 – Enzymes – Factors affecting enzyme activity – pH

• Substances that tend to decrease the activity of enzymes are called inhibitors.
• An inhibitor is a chemical substance which can react (in place of substance) with the enzyme but is never transferred into products by
blocking the active site of enzyme temporarily or permanently.
• Poisons like cyanide, antibodies, anti-metabolics and some drugs are typical examples of inhibitors.
• Inhibitors can be divided into two types:
o The irreversible inhibitors occupy the active site by forming covalent bond or they may physically block the active site, where they decrease the
reaction rate by occupying the active sites or destroying the globular structure of enzymes.
o The reversible inhibitors form weak linkages with the enzyme and their effect can be neutralized completely or partly by an increase in the
concentration of substrate.
• In an enzyme catalyzed reaction, the inhibitors may decrease the activity of enzymes and thus the rate of reaction either by combining
directly with the enzyme or by reacting with the activator, so that the activator does not remain available to enzyme for activation.
• One type of reversible inhibitors, called competitive inhibitors, compete with the substrate to form ES complex but do not give any product.
o Such inhibitors have structural similarity with substrate, are bound to either the catalytic or active site of enzyme and are called competitive
inhibitors.
• Another type of reversible inhibitors, called non-competitive inhibitors cause non-competitive inhibition.
o Here the inhibitor is not bound to the catalytic or active site but to some other site of enzyme, which distorts the enzyme’s structure and also affects
the catalytic site of the enzyme in such a way that even if genuine substrate binds to the active site, catalysis fails to take pace.
• Note that competitive and non-competitive inhibitors are both types of reversible inhibitors.
• In the reactions catalyzed by enzymes, irreversible inhibitors cause irreversible inhibition either by physically blocking the active sites of
enzymes or by occupying the active sites and forming covalent bonds.
o So the rate of reaction is retarded due to the occupation of active sites of enzymes by irreversible inhibitors or due to the destruction of the globular
structure of enzymes.
21.3.2.4 – Enzymes – Factors affecting enzyme activity – Role of
inhibitors in enzyme catalyzed reactions

• Succinic acid (substrate) is converted into Fumaric acid (product) by the
enzyme succinic dehydrogenase.
• But in the presence of malonic acid (competitive inhibitor), having structural
similarity with succinic acid (substrate), the binding sites are occupied by
the malonic acid but no catalysis takes place at the active or catalytic site,
hence no product is formed.
21.3.2.4.1 – Enzymes – Factors affecting enzyme activity – Role
of inhibitors in enzyme catalyzed reactions - Example
Succinic dehydrogenase + succinic acid Funaric acid + succinic dehydrogenase
substrateenzyme product enzyme
Succinic dehydrogenase + malonic acid No reaction possible
competitive inhibitorenzyme enzyme blocked

• Enzymes are extensively used in different
industries for fast chemical reactions because
o they enable faster chemical reactions saving time
and money and/or
o bring down the temperature requirement for
reactions, making some reactions possible that
would not be possible without the enzyme.
• For example:
o In food industry, enzymes that break starch into
simple sugars are used in the production of white
breads and buns, etc.
o In brewing industry, enzymes are used to break
starch and proteins, whose products are then used
by yeast for fermentation to produce alcohol.
o In paper industry, enzymes break starch to lower its
viscosity that aids in making paper.
o As biological detergents, protease enzymes are used
for the removal of protein stains from clothes and
amylase enzymes are used in dish washing to
remove resistant starch residues.
21.3.3 – Enzymes – Industrial applications

• What are enzymes? Why are they called biocatalysts?
• How does enzyme work?
• Who has used the term Enzyme first?
• Why are the following scientists famous for?
o Emil Fischer
o Daniel Koshland
• “Enzymes are extensively used in different industries”. Comment on this
statement.
20.6.7 – Nitriles - Quick quiz

21.3 - Enzymes
Dr. Hashim Ali
Education (FBISE)
Chemistry F.Sc
II

Dr. Hashim Ali
21.4 – Lipids
Education (FBISE)
Chemistry F.Sc
II

• The word “Lipids” is originated from Greek “Lipos” meaning fat!
• Lipids are naturally occurring organic compounds of animals and plant origin,
which are soluble in organic solvents and belongs to a heterogeneous group of
substances.
• These molecules consist of carbon, hydrogen, and oxygen atoms.
• Lipids are the main constituents of all membranes in all cells (cell walls in
plants), food storage molecules, intermediaries in signaling pathways, Vitamins
A, D, E and K, and cholesterol.
• All lipids are hydrophobic: that is the one property they have in common.
• Fats and oils are made from two kinds of molecules.
o Glycerol ( a type of alcohol with a hydroxyl group on each of its three carbons).
o three fatty acids joined by a dehydration synthesis.
• Since there are three fatty acids attached, so these are known as triglycerides.
21.4.0 – Lipids – Introduction

• There are three broad classes of lipids.
o Simple lipids
o Compound lipids
o Derived lipids
21.4.1 – Lipids – Classification

• These are the esters of fatty acids with glycerol.
• Typical example of simple lipids are triglyceride, which are found as
o neutral fats in adipose tissue, butter fat, fish oils, olive oil, and corn oil.
o waxes in bees wax, head oil of sperm whale, carnauba oil, and lanolin of industrial
and medicinal importance.
21.4.1.1 – Lipids – Classification – Simple lipids

• These contain radicals in addition to fatty acids and alcohols.
• Typical example of complex lipids are
o phospholipids (phosphatides): Found chiefly in animal tissues.
o plasmahalogen: Found in brain, heart, and muscle.
o lipositol: Found in brain, heart, kidneys, and plant tissues together with phythic
acid with typical example, phosphatidyl inosotol, a phosphatide linked to inositol
known for rapid synthesis and degradation in brain and for which there is evidence
for role in cell transport processes.
o sphingomyelin: Found in nervous tissue, brain, and red blood cells, and is a source
of phosphoric acid in body tissue.
21.4.1.2 – Lipids – Classification – Compound lipids

• Derived lipids are hydrolytic product of compound lipids.
• The typical example of derived lipids are fatty acids.
• Fatty acids occur in plant and animal foods and also exhibit complex forms
with other substances.
• Fatty acids are obtained from hydrolysis of fats, usually contain an even
number of carbon atoms and are straight chain derivatives.
• The unsaturated (containing at least 1 C = C or C ≡ C bonds) fats are
healthier than the saturated (no C = C or C ≡ C bonds) ones.
21.4.1.3 – Lipids – Classification – Derived lipids

• Lipids are generally defined in terms of solubility,
and not in terms of particular structures, as in the
cases of proteins and nucleic acids.
• Lipids associate with one another via Van der
Waals forces and the hydrophobic effect.
• In particular we discuss the structure of fatty acids.
• The tail of a fatty acid is a long hydrocarbon chain,
making it hydrophobic.
• The “head” of the molecule is a carboxyl group
which is hydrophilic.
• Fatty acids are the main component of soap where
their tails are soluble in oily dirt and their heads
are soluble in water to emulsify and wash away the
oily dirt.
• However, when the head end is attached to glycerol
to form a fat, the whole molecule is hydrophobic.
21.4.2 – Lipids – Structure
+ 3H2O
glycerol
3 fatty acids
Triglyceride

• Oils and fats may be either liquids or non-crystalline solids at room temperature.
• Fats and oils in the pure states are colorless, odorless and tasteless.
• The color of the fats arises due to foreign substances, for example yellow color of
the butter is due to the presence of keratin.
• They are lighter than water.
• They are insoluble in water.
• They are readily soluble in organic solvents like diethyl ether, carbon disulfide,
acetone, benzene, chloroform and carbon tetrachloride.
• They form emulsions when they are agitated with water in the presence of soap
or other emulsifier.
• Fats and oils are poor conductor of heat and electricity, and serve as excellent
insulator for the animal body.
21.4.3.1 – Lipids – Properties – Physical properties

• Fats and oils undergo various types of reactions but the most important are:
o Hydrolysis
o Saponification
o Hydrogenation
21.4.3.2 – Lipids – Properties – Chemical properties

• Fats and oils are triglycerides.
• They are tri-esters.
• They are hydrolyzed by enzymes, which act as catalysts. These enzymes are
called lipases.
• Actually this hydrolysis takes place in the digestive tract of human beings and
animals.
• Fatty acids are produced in animal body which play an important role in the
metabolic pathways.
21.4.3.2.1 – Lipids – Properties – Chemical properties –
Hydrolysis of fats and oils
Lipase
triglyceride glycerol fatty acids

• Saponification is the hydrolysis of triglycerides (oils or fats) by alkalies.
• Glycerol is produced along with sodium or potassium salt of fatty acids.
• These Na and K salts are called soap (salt of fatty acid).
Saponification
triglyceride glycerol
soaps

• We know that unsaturated triglycerides are liquids at room temperature.
• They are called unsaturated as they can be saturated by passing hydrogen in them in the
presence of metal catalysts.
• This leads to the conversion of liquid triglycerides into a semi solid triglyceride.
• In this way, liquid triglycerides are converted into a semi solid triglyceride.
• This reaction is used to commercially harden the vegetable oil, for the production of
vegetable ghee or margarine.
• Hardened oils are also used extensively for making soaps and candles.
• trans fats are rare in nature, but are readily produced in an industrial procedure called
partial hydrogenation.
• In this process, hydrogen gas is passed through oils (made mostly of cis-unsaturated fats),
converting some – but not all – of the double bonds to single bonds.
o The goal of partial hydrogenation is to give the oils some of the desirable properties of saturated
fats, such as solidity at room temperature, but an unintended consequence is that some of
the cis double bonds change configuration and become trans double bonds.
o Trans-unsaturated fatty acids can pack more tightly and are more likely to be solid at room
temperature.
• Partial hydrogenation and trans fats might seem like a good way to get a butter-like
substance at oil-like prices.
o Unfortunately, trans fats have turned out to have very negative effects on human health.
Catalytical hydrogenation/Hardening of oils
Glycerol
trioleate
Glyceryl
tristearate

• Lipids play three major biochemical roles.
o As a storage form for metabolic energy (triglycerides).
o As components of membranes.
o As messengers (prostaglandins, steroid hormones).
• A major role of lipids in nutrition is to provide energy, since unsaturated, saturated and trans fats all provide
about 9 cal per gram compared to carbohydrate or protein with 4 calories per gram.
• Even though it is high in calories, fat does not necessarily cause weight gain if you monitor your total intake.
• Our body also needs fat from our diet to be able to absorb and use fat-soluble essential nutrients such as
vitamin A, vitamin D and vitamin E.
• Some other functions of lipids are:
o Tissue reconstruction
o Nervous system organization
o Increases and assures a normal function of the skin.
o Antibodies formation.
o Good function of endocrine glands (thyroid)
o Water metabolism
21.4.4 – Lipids – Nutritional and biological importance

• Some nutrients are essential in our diet because we need them for good health but our
body can not produce them.
o The essential lipids are polyunsaturated fats called omega-6 and omega-3 fats.
o We need these fats for hormone synthesis, cell membrane structure and healthy fatty acids from
vegetable oils and nuts.
o Omega-3 fatty acids are also in flaxseed, walnuts and fatty fish.
• Mono-saturated fatty acids are not essential in our diet because our body can synthesize
them but they may help reduce our risk for heart disease.
o They are naturally found in olive oil, peanuts and avocadoes.
o We do not need to get saturated fat, trans fat or cholesterol in our diet, and these lipids raise bad
cholesterol levels in our blood.
o Saturated fat is in fatty meats and cheese, palm and coconut oil, and butter.
o Trans fat is in partially hydrogenated oils in processed and fried foods, while cholesterol is present
in fatty animal foods.
o Our bodies make about 2g of cholesterol per day, and that makes up about 85% of blood
cholesterol, while only about 15% comes from dietary sources.
21.4.4.1 – Lipids – Nutritional and biological importance –
Essential and non-essential lipids

• What are lipids? Shortly explain the only property that all the lipids have
in common.
• What are triglycerides? Draw its structure.
• Explain briefly the structure of lipids.
21.4.5 – Lipids – Quick quiz

21.4 - Lipids
Dr. Hashim Ali
Education (FBISE)
Chemistry F.Sc
II

Dr. Hashim Ali
21.5 – Nucleic acids
Education (FBISE)
Chemistry F.Sc
II

• Nucleic acids, and DNA in particular, are key macromolecules for the continuity of life.
o DNA bears the hereditary information that’s passed on from parents to children, providing instructions for how
(and when) to make the many proteins needed to build and maintain functioning cells, tissues, and organisms.
o How DNA carries this information, and how it is put into action by cells and organisms, is complex, fascinating,
and fairly mind-blowing, but out of scope for this class. Here, we’ll just take a quick look at nucleic acids from the
macromolecule perspective.
• The molecules that preserve the hereditary information and that transcribe and translate that information in
a way that allows the synthesis of all the varied enzymes of the cell are called nucleic acid.
• Nucleic acids were first discovered in the nuclei of puss cells in 1868 by Friedrich Miescher.
• They were also found in sperm heads in 1872.
• There are two types of nucleic acids:
o Deoxyribonucleic acids (DNA)
o Ribonucleic acids (RNA)
• In human body, the nucleic acids occur as part of the conjugated proteins which are called nucleoproteins.
• The nucleic acids direct the synthesis of proteins.
21.5.0 – Nucleic acids – Introduction

• The basic structure of nucleic acids were examined
by the biochemist P.A. Levene, who found that DNA
contains three main components.
o Five carbon sugars
o Nitrogen containing bases.
o Phosphate (PO4) groups.
• Levine concluded that DNA and RNA molecules are
made of repeating units called nucleotides.
• In a nucleotide, nitrogen base is attached to carbon
number 1 of a pentose sugar and phosphate group is
attached to carbon number 5 of the sugar.
• In addition a free hydroxyl (–OH) group is attached
to the 3’ carbon atom.
21.5.1 – Nucleic acids – Structural components of DNA and RNA

• The phosphate and the 3’ hydroxyl groups allow DNA and RNA to form long
chains of nucleotides because these two groups can react chemically with
one another.
• The reaction between the phosphate group of one nucleotide and the
hydroxyl group of another is a dehydration synthesis, eliminating a water
molecule and forming a covalent bond that links the two groups.
• The bond is called a phosphodiester bond because the phosphate group is
linked to the two sugars by means of a pair of ester (P–O–C) bonds.
• The two unit polymer resulting from this reaction still has a free 5’
phosphate group at one end and a free 3’ hydroxyl group at the other, so that
it can bond with other nucleotides.
• In this way, many thousands of nucleotides can bond together in long
chains.
• Linear strands of DNA or RNA, no matter how long they are, will almost
always have a free 5’ phosphate group at one end and a free 3’ hydroxyl
group at the other.
• It is analyzed that the amount of adenine in DNA always is the same as the
amount of thymine, and the amount of guanine always equals the amount of
cytosine, which implies that there is always equal proportion of purine
(A+G) and pyrimidine (C+T).
• The X-ray diffraction pattern suggested that the RNA molecule had a shape
of a helix with a diameter of 2 nm and a complete helical turn every 3.4 nm.
21.5.1 – Nucleic acids – Structural components of DNA and RNA

• RNA contains ribose sugar while
DNA contains deoxyribose sugar.
• Nitrogenous bases in DNA are
cytosine, thymine, adenine and
guanine, while in RNA cytosin,
uracil, adenine and guanine are the
four nitrogenous bases.
• DNA is double stranded while RNA
is single stranded.
21.5.2 – Nucleic acids – Differences between RNA and DNA

• Write the names of structural components of DNA and RNA.
• Differentiate between purines and pyrimidines.
• Which purines are present in both DNA and RNA?
21.5.3 – Nucleic acids – Quick quiz

21.5 - Nucleic acids
Dr. Hashim Ali
Education (FBISE)
Chemistry F.Sc
II

Dr. Hashim Ali
21.6 – Minerals of biological significance
Education (FBISE)
Chemistry F.Sc
II

• Minerals are the nutrients that exist in the body, and are as essential as our need
for oxygen to sustain life.
• Minerals are also found in organic and inorganic combinations in food.
• In the human body, only 5% of the body weight is mineral matter, but it is vital
to all mental and physical processes and for total well being.
• They are most important factors in maintaining all physiological processes,
constituents of the teeth, bones, tissues, blood, muscle, and nerve cells.
• Acting as catalysts for many biological reactions within the human body, they are
necessary for transmission of messages through the nervous system, digestion
and metabolism for utilization of all nutrients in food.
• Vitamins can not be properly assimilated without the correct balance of
minerals, e.g., calcium is needed for vitamin “C” utilization, zinc for vitamin A,
magnesium for B complex vitamins, selenium for vitamin E absorption etc.
21.6.0 – Minerals of biological significance - Introduction

21.6.1 – Minerals of biological significance – Important minerals
Important minerals in human diet and their roles
Minerals Role in body Importance
Sodium Fluid balance in body
Helps in absorption of other nutrients
Important for muscle contraction, nerve
impulse transmission, heart function and
blood pressure
Potassium Fluid balance in body
Acts as cofactor for enzymes
Chloride Fluid balance in body
Component of hydrochloric acid
Calcium Development and maintenance of bones and teeth and blood clotting
Magnesium and
phosphorus
Development and maintenance of bones and teeth
Iron Oxygen transport and storage Acts as enzyme cofactor
Support immune function
Zinc Aids insulin action
Helps in growth and reproduction
Manganese Acts as enzyme cofactor
Chromium Helps in insulin action
Fluoride Stabilizes bone mineral and hardens tooth enamel
Iodine Essential for normal thyroid function

• A crucial mineral for bone growth and formation, calcium is useful in regulating blood
pressure and cholesterol levels, and in maintaining heart health.
• It is useful for blood clotting, nerve and muscle functioning.
• It also plays a significant role in milk production during pregnancy.
21.6.1.1.1 – Minerals of biological significance – Important
minerals – Calcium – Significance
• Calcium is the most common mineral in the human
body where it is present in almost the same relative
abundance as in the earth’s crust.
• There are six stable isotopes of calcium: calcium40 is
the most common (97%) and calcium46 the least
abundant (0.003%).
• The integrity of the system depends critically on
vitamin D status; if there is a deficiency of vitamin D,
the loss of its calcemic action leads to a decrease in the
ionized calcium and secondary hyperparathyroidism
and hypophosphatemia.
• This is why experimental vitamin D deficiency results
in rickets and osteomalacia whereas calcium deficiency
gives rise to osteoporisis.
• Approximately 99% of the total body calcium is in the
skeleton and teeth, and 1% in blood and soft tissues.
• Calcium has 4 major biological functions.
o Structural as stores in the skeleton.
o Electrophysiological – carries charge during an action
potential across membranes.
o Intracellular regulator, and
o as a cofactor for extracellular enzymes and regulatory
proteins.

• We get calcium from
o milk
o cheese
o egg yolk
o beans
o nuts
o cabbage etc.
minerals – Calcium– Source and deficiency
• A deficiency may result in
o arm and leg muscle spasms
o softening of bones
o back pain and leg cramps
o brittle bones
o rickets
o poor growth
o osteoporosis
o tooth decay and
o mental depression

• Iron is an essential mineral.
• Its major function is to combine with protein and copper in making hemoglobin, the component of the blood
that carries oxygen from the lungs to the tissues throughout the body.
• It also regulates growth and supports the immune system.
minerals – Iron– Significance
• To prevent fatigue, iron is needed by the body to make
hemoglobin rich blood, which transports oxygen to the cells.
• It is also needed for adenosine triphosphate (ATP) production,
which is essential for cellular energy and proper cell function.
• Iron is lost through sweat and through bleeding of the digestive
tract from the harsh motion of exercise.
• Studies indicate that 34% of female runners and 8% male
runners are iron deficient.
• Iron is needed for proper placenta development and also for the
prevention of pre-term and low birth weight babies.
• Studies estimate that up to 58% of pregnant women are iron
deficient.
• Iron is essential during the first months for brain growth and the
effects of anemia maybe associated with developmental delays in
both motor and cognitive abilities.
• Up to six months to restore low iron stores, its sufficient quantity
must be used.
• When iron deficiency is left untreated, it can lead to more serious
conditions.
• Iron plays an important part in the metabolic processes of
animals.
• The function of iron in the body is limited almost exclusively to
the oxygen transport in the blood, through hemoglobin.
• It is present in some enzymes that catalyze reactions of cellular
oxidation.
• In human, the richest organs in iron are liver and spleen.
• In smaller amounts, it is also present in medulla, kidneys and
intestines.

• We get iron from
o red meat
o egg yolk
o whole wheat
o fish
o spinach
o mustard etc.
minerals – Iron– Source and deficiency
o weakness
o fatigue
o paleness of the skin
o constipation and
o anemia

• After calcium, phosphorus is the second most abundant mineral in the body.
• It is a principal mineral of bones and teeth.
• Phosphorus is involved in most metabolic actions in the body including kidney functioning, cell growth and
the contraction of the heart muscle.
minerals – Phosphorus – Significance
• It also assists in the contraction of muscles, in the
functioning of kidneys, in maintaining the regularity of
the heartbeat and in nerve connections.
• Phosphorus works in conjunction with B vitamins.
• It plays an important role in the body’s utilization of
carbohydrates and fats, and in the synthesis of protein
for the growth, maintenance, and repair of bones and
teeth.
• The main function of phosphorus is in the formation of
bones and teeth.
• It is also crucial for the production of ATP, a molecule
the body uses to store energy.
• Phosphorus is present in plants and animals.
• There is over 1 lb (454 grams) of phosphorus in the
human body.
• It is a component of adenosine triphosphate (ATP), a
fundamental energy source source in living things.
• It is found in complex organic compounds in the
muscles and nerves, and in calcium phosphate, the
principal material in bones and teeth.
• Phosphorus compounds are essential in the diet.
• Organic phosphates, ferric phosphates and calcium
phosphates are added to foods.
• Dicalcium phosphate is added to animal feeds

• We get phosphorus from
o egg yolk
o cheese
o milk
o cabbage etc.
minerals – Phosphorus– Source and deficiency
• A deficiency is unusual but may result
in
o loss of appetite,
o anxiety,
o bone pain,
o fragile bones,
o stiff joints,
o fatigue,
o irregular breathing,
o numbness,
o weakness, and
o weight change
o In children, decreased growth and poor
bone and tooth development may
occur.

• Zinc is vital to immune resistance, wound healing, digestion, reproduction, physical growth,
diabetes control, taste and smell, and maintaining normal Vitamin A levels and usage.
• Zinc can be found in almost every cell of the body and serves as part of more than 70 enzymes
that control body processes.
minerals – Zinc – Significance
• Zinc is the most important of all trace elements
involved in human metabolism.
• More than hundred specific enzymes require zinc for
their catalytic function.
• If zinc is removed from the specific site, enzyme
activity is lost; replacement of zinc restores activity.
• Studies in individuals with dermatitis enteropathica, a
genetic disorder with zinc malabsorption resulting in
severe deficiency, have provided much insight into the
functional outcomes of zinc deficiency.
• These include impairments of dermal, gastrointestinal,
neurologic and immunologic systems.
• Loss of zinc through gastrointestinal tract accounts for
approximately half of all zinc eliminated from the body.
• Considerable amount of zinc is secreted through the
biliary and intestinal secretions, but most of it is
reabsorbed, and this process is an important point of
regulation of zinc balance.
• Other routes of zinc excretion include the urine and
surface losses (desquamated skin, hair, sweat).

• We get zinc from
o oyster
o red meat
o chicken
o beans
o nuts
o dairy products and
o some sea foods etc.
minerals – Zinc– Source and deficiency
o poor growth
o acne like rash
o hair loss
o diarrhea
o delayed sexual maturation
o impotence
o sterility
o eye lesions
o loss of appetite
o reduced sense of taste and smell
o skin lesions and inflammation
o poor wound healing
o reduced resistance to infections
o mental confusion
o poor learning ability
o changes in hair and nails
o anemia

• What is biological significance of mineral?
• Define mineral. Give its percentage present in human body.
• Minerals of which metals are required for assimilation of vitamins B, C and E.
• What problems are caused by deficiency of calcium and Phosphorus?
• Give importance of zinc mineral.
• Give significance of
o Keralin
o Mysoin and fibrin fibrous protein.
• How much intake of manganese should be per day?
• How hibernating animals obtain energy during hibernation?
• Give few macro and micro minerals.
• How much sodium and potassium should be taken per day?
• What is insulin?
20.6.7 – Minerals of biological significance – Quick quiz

21.6 - Minerals of biological significance
Dr. Hashim Ali
Education (FBISE)
Chemistry F.Sc
II

• Glycogen – a power house
o Glycogen is a reserved food material that is stored in muscles and liver in animals and human.
o When body requires energy due to lack of glucose, the glycogen is reconverted into glucose and provides energy to the body in the
form of ATP.
• Hibernating animals and reserve food
o Large amount of fat is stored in the body of some animals that hibernate during winter.
o In winter, the metabolic activities slow down.
o They use this fat as reserved food material that produce ATP on oxidation.
• Complex carbohydrates which lubricate the elbow and knee
o Glucosamine, glucosaminoglycons or proteoglycan are the complex carbohydrates which provide lubrication to elbow and knee.
o Glucosamine (C6H13NO5) is an amino sugar, which is produced naturally in the body and plays a key role in building cartilage and
lubricating joints.
o It is found in the fluid that is around joints and is a prominent precurser for glycosaminoglycans and for glyeosaylated proteins and
lipids.
o Gluasamine has been shown to help keep our joints resilient and healthy by lubricating and resting the connective tissue.
o It is a naturally occurring nutrient and is a glutamine derivative that retains an amine group and a sugar molecule (glucose).
o Over time, every day wear and tear, less than perfect nutrition, injuries and aging can result in dry, brittle cartilage which is
vulnerable to damage and stiffening.
o Research has shown that glucosamine may repair damaged or strained connective tissue.
o Our joints are made up of two thirds of water yet are not able to attract and retain it.
o Glucosamine has shown to help keep cartilage resilient and healthy by attracting and holding water and nutrients within this matrix.
o Studies have even shown glucosamine may even help to regenerate new cartilage once it becomes damaged thereby restoring joint
function and mobility.
o Because of its ability to help to lubricate and restore elbow and knee joints, it is quite popular with weight trainers, sports enthusiasts
etc.
Society, Technology and Science

• Complex carbohydrates which lubricate the elbow and knee
o Glucosaminoglycans (GAGs) are the most abundant hetropolysaccharides in the body.
o They are long unbranched molecules containing a repeating disaccharide unit.
o Usually one sugar is uronic acid and the other is either GIcNAc or CalNAc.
o GAGs have negative charge on them and are a major component of joint cartilage.
o Chondroitin sulfate (D. glucuronate + CalNSc sulfate) is the most abundant GAG found in cartilage.
o Keratin sulphate (Gal + GicNAc sulfate) is often aggregated with chondroitin sulfate.
o GAGs have unique properties, i.e., the ability to fill space, bind and retain water and repel negatively charged
molecules.
o Because of high viscosity and low compressibility, they are ideal for a lubricating fluid in the joints especially in
the knee and elbow.
o On the other hand, their rigidity provides structural integrity to the cells.
o Proteoglycans (mucoproteins) are formed of GAGs and core proteins, covalently bonded to each other, which
are found in all connective tissues.
o Proteoglycans can also be called joint grease and appear to be a necessary compound in synovial fluid for
normal joint lubrication and function, where the synovial fluid is a clear pale yellow fluid, the main function of
which is to serve as a lubricant in joints or tendon sheath.
o Aggrecan is one of the most important extra cellular proteoglycan.
o To each aggrecan core protein, multiple chains of chondroitin sulfate and keratin sulfate are covalently
attached through the trisaccharide linker and play an important role in hydration of cartilage of joints.
o They give cartilage its gel like properties, i.e., lubricate it and provide resistance to deformation.

• Fibrous proteins from hair and silk
o Keratin is one of a family of fibrous structural proteins and is the key structural material making up hair, horns, claws, hooves, and
the outer layer of human skin.
o Keratin is also the protein that protects epithelial cells from damage or stress.
o Keratin is extremely insoluble in water and organic solvents.
o It plays structural or supporting role in the body.
o Examples are silk fiber, keratin, (of nail, and hair), myosin (of muscle cells), fibrin of blood clot.
• Insulin – a protein hormone whose deficiency leads to diabetes mellitis
o Insulin is a 51 amino acid peptide hormone that is produced exclusively by pancreatic beta cells.
o F. Sangar was the first scientist who determined the sequence of amino acids in insulin.
o After 10 years of careful work, he concluded that insulin is composed of up to 51 amino acids in two chains, one alpha chain and
one beta chain.
o The alpha chain contains 21 amino acids and the beta chain contains 30 amino acids.
o Both chains are held together by disulfide bridges and the molecular weight of insulin is 5808.
o Insulin hormone is central in regulating carbohydrate and fat metabolism in the body and causes the cells in liver, muscles and fat
tissue to take up glucose from the blood.
o In the liver and skeletal muscles, glucose is stored as glycogen, while in adipocytes, it is stored as triglycerides.
o Insulin stops the use of fat as energy source.
o When blood glucose level falls below a certain limit, the body begins to use stored sugar as an energy source through
glycogenolysis.
o As a central metabolic control mechanism, its status is also used a control signal to other body systems such as amino acids uptake
by body cells.
o In addition it has several anabolic effects throughout the body and is used medicinally to treat some forms of diabetes patients.

• Role of minerals in the body
o Minerals act as cofactors for the enzyme reactions, i.e., enzymes do not work without minerals and all
cells require enzymes to work and function; they give us our vitality.
o They maintain the pH balance within the body.
o Minerals actually facilitate the transfer of nutrients across cell membranes.
o They maintain proper nerve conduction.
o Mineral help to contract and relax muscles.
o They help to regulate our bodies’ tissue growth.
o Minerals provide structural support for the body.
• There are two categories of minerals essential with in body, macro-minerals and micro-
minerals.
• There is no mineral deficiency – they all must be maintained in balance within the body.
• Macro minerals include Calcium, Chloride, Phosphorus, Sodium, Potassium, Sulfur and
Magnesium.
• The micro-minerals or trace minerals include Iron, Boron, Chromium, Iodine, Manganese,
Molybdenum, Selenium, Silicon, Copper, Cobalt, Rubidium, Germanium, Lithium, Zinc and
Vanadium.

• Structure and function of minerals
o The term mineral is applied to chemical elements present in the ash of calcined tissue.
o Dietary minerals are present in inorganic salts or as part of carbon containing organic compounds.
o For example, magnesium is present in chlorophyll, the pigment that makes plants green.
o Six minerals are required by people in gram amount: sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), phosphorus (P),
and chlorine (Cl), where the daily requirements range from 0.3 to 2.0 grams per day.
o Nine trace mineral are required by people in minute amounts: chromium (Cr), copper (Cu), iodine (I), iron (Fe), fluorine (F),
manganese (Mn), molybdenum (Mo), selenium (Se), and zinc (Zn). There are additional requirements for cobalt (Co) but these are
generally expressed in terms of the cobalt containing vitamin B12.
o All trace minerals are toxic at high levels.
• Calcium
o Calcium is the most abundant mineral in the human body, where more than 99% of total body calcium is sorted in the bones and
teeth.
o Calcium is also found in body fluid where its function is to regulate contractions of blood vessels and muscles.
o The requirement for calcium is greatest from puberty to maturity, when the body grows very quickly.
o Milk and dietary products are good sources of calcium.
• Fluorine
o Most of the body’s fluorine is contained in bones and teeth, and the main source of fluoride is drinking water.
o Fluorine hardens tooth enamel and effectively prevents dental caries.
o Excessive fluorine in drinking water can accumulate in teeth and bones, causing fluorosis.
o Permanent teeth that develop during high fluorine intake have irregularly distributed chalky patches on the surface of the enamel
which becomes stained yellow or brown, producing a characteristic mottled appearance.

• Iodine
o Iodine (I) is primarily involved in the synthesis of two thyroid hormones,
thyrosine and triiodothyronine.
o In adults, about 80% of the iodide absorbed is trapped by the thyroid gland.
o Most environmental iodine occurs in seawater, so people living far from the sea
are at particular risk of deficiency.
o Salt fortified with iodide (typically 70 microgram per gram) helps ensure
adequate intake (100 microgram per day) but the deficiency is rare in areas
where iodized is used.
o Iodine deficiency develops when iodide intake is less than 20 microgram per
day.
o In mild or moderate deficiency, the thyroid gland hypertrophies to concentrate
iodine in itself, resulting in goiter which is an enlargement of the thyroid gland
visible as a swelling of front of the neck.
o Excessive iodine consumption can lead to thyrotoxicosis, a condition resulting
from high concentrations of thyroid hormones in the body, which can result
from eating foods that have high amounts of iodine, such as kombu-type
seaweed.
thyrosine

• Iron
o Iron (Fe) is a component of hemoglobin, myoglobin, and many
enzymes in the body.
o Heme iron, contained mainly in animal products is absorbed much
better than non-heme iron, which accounts for over 85% of iron in the
average diet.
o However, absorption of non-heme iron is increased when it is
consumed with animal protein and vitamin C.
o The Recommended Daily Allowance (RDA) of iron is 8 milligrams for
men and postmenopausal women.
o Iron deficiency, which may be caused by improper vegan or ovo-lacto
vegetarian diets.
o Chronic bleeding may also cause iron deficiency and iron may
accumulate in the body when a person is given repeated blood
transfusions or takes an overdose of iron supplements.
o Excess iron is toxic and damages the intestines and other organs as
well as cause vomiting and diarrhea.
heme in hemoglobin

• Magnesium
o Magnesium (Mg) has several important metabolic functions in the production and transport of energy.
o It is also important for the contraction and relaxation of muscles.
o Magnesium is involved in the synthesis of protein, and it assists in the functioning of some enzymes.
o Most dietary magnesium comes from nuts, cereals and dark green leafy vegetablem which are rich in
chlorophyll.
• Manganese
o Manganese (Mn) is necessary for healthy bone structure and is a component of several enzyme systems
including manganese-specific glycosyltransferases and phosphoendolpyruvate caboxyl kinase.
o Manganese is found in cereal and nuts and the adequate intake of manganese is 2 to 5 milligram per
day.
• Molybdenum
o Molybdenum (Mo) is a component of coenzymes necessary for the activity of xanthine oxidase, sulfite
oxidase, and aldehyde oxidase.
o Sulfite oxidase catalyzes the transformation of sulfite to sulfate, which is necessary for the metabolism
of sulfur containing amino acids, such as cysteine.
o Legumes such as lentils, beans, and peas are good sources of molybdenum.

• Potassium
o Potassium (K) maintains fluid volume inside and outside of cells, and acts to blunt the rise of blood pressure in
response to excess sodium intake.
o The adequate intake of potassium is 4.5 grams per day for children 9 to 13 years old and 4.7 grams per day for
older persons.
o Potassium is generally found in fruits and vegetables, dried peas, dairy products, meats and nuts.
o Potassium from supplements or salt substitutes can result in hyperkalemia and possibly sudden death if excess
is consumed by individuals with chromic renal insufficiency (kidney disease).
• Selenium
o Selenium (Se) is a part of the enzyme glutathione peroxides, which metabolizes hydro peroxides formed from
poly unsaturated fatty acids.
o Selenium is also a part of the enzyme deiodinate thyroid hormones.
o Generally selenium acts as an antioxidant that works with vitamin E.
o Deficiency of selenium causes Keshan disease which is a form of congenital chardiomyopathy.
o The RDA for selenium is 70 micrograms (mcg) and the tolerable upper level for selenium is 400 mcg/day for
adults based on the prevention of hair and nail brittleness and signs of chronic selenium toxicity.
• Sodium
o Sodium (Na) is usually consumed as table salt (sodium chloride, NaCl).
o The adequate intake of 1.5 grams per day with an upper limit of 2.3 grams per day is calculated to meet the
needs of sweat loss for individuals 8 years or older engaged in recommended levels of physical activity.
o Active people in humid climates who sweat excessively may need more than the adequate intake.

• Zinc
o Zinc (Zn) is contained mainly in bones, teeth, hair, skin, liver, muscle,
leukocytes, and testes.
o Zinc is a component of several hundred enzymes, including many nicotinamide
adenine dinucleotide (NADH) dehydrogenases, RNA and DNA polymerases,
and DNA transcription factors as well as alkaline phosphatase, super oxide
dismutase, and carbonic anhydrase.
o Good dietary sources of zinc include mollusks, such as oysters, and cereals.

 Carbohydrates are the most abundant macromolecule on earth. They are of three
types, i.e., monosaccharides, disaccharides and polysaccharides.
 People eating a diet high in carbohydrates are less likely to accumulate body fat
compared with those who follow a low carbohydrate/high fat diet.
 Proteins are the most important class of biomolecules. They are major structural
components of animal and human tissues. They are classified as a simple protein,
conjugated protein and derived proteins. They are actually the polymers of amino
acids.
 Nucleoproteins act as carrier of heredity from one generation to the other.
 Hemoglobin is a protein and carrier of oxygen. Some of the proteins act as hormones.
 Enzymes are biocatalyst and catalyze chemical reactions in living organisms. They are
quite specific in their function. Their activity depends upon temperature, substrate
concentration and pH. They are protein in nature and are used extensively in food
brewing and paper industry.
Key Points

 All lipids are hydrophobic. Fats are solid while oils are liquid at room
temperature. They are insoluble in water while soluble in organic solvents
such as diethyl ether, acetone and benzene etc.
 Some lipids are essential for our diet and some are non-essential.
 Nucleic acids are present in every living cell as well as viruses. They have the
ability to reproduce, store and transmit genetic information. They are of two
types: DNA and RNA. Nucleotide is the structural unit of DNA and consists of
one sugar, one nitrogenous base and at least one phosphate.
 Minerals are the nutrients that are as necessary as oxygen for life. They are
constituents of teeth, bones, tissues, blood, muscles and nerve tissues.
 Minerals are classified as major and trace minerals, i.e., those required in
appreciable quantity are major and those required in low quantity are trace.
Key Points

1. Biochemistry covers the practical
applications of
a. Medicine
b. Agriculture
c. Nutrition
d. All of these
2. Macromolecules are of how many
types
1. Three
2. Four
3. Five
a. Six
1. Select the right answer from the choices given
3. The general formula for
carbohydrate is
a. Nn(H2O)n
b. Pn(H2O)n
c. Cn(H2O)n
d. Hn(CO2)n
4. Most organic matter on earth is
made up of
1. Carbohydrates
2. Lipids
3. Olive oils
4. Proteins

5. The number of carbon atoms in
hexose is
a. One
b. Four
c. Six
d. Ten
6. The long chains of amino acids
are called
a. Oils
b. Polypeptides
c. Proteins
d. Monopeptides
7. Proteins are used in both forms of
a. Catabolism
b. Anabolism
c. Enzymes
d. Metabolism
8. What is true about enzymes?
a. They make biochemical reaction to
proceed spontaneously
b. They lower the activation energy of a
reaction
c. They are not very specific in their
choice of substrates.
d. They are needed in large quantities.

9. To what category of molecules do
enzyme belong?
a. Carbohydrates
b. Lipids
c. Nucleic acids
d. Proteins
10.What is true about cofactors?
a. Break hydrogen bonds in proteins
b. Increase activation energy
c. Help facilitate enzyme Activity
d. Are composed of proteins
11. Prosthetic groups are
a. Required by all enzyme
b. Loosely attached with enzymes
c. Proteinic nature
d. Tightly bound to enzyme
12.Lipids are generally defined in
terms of
a. Solubility
b. Structure
c. Molarity
d. All of these

13.DNA and RNA are made up of:
a. Peptides
b. Nucleotides
c. Neurons
d. None of these
14.____ of the human body weight
is mineral matter.
a. 5%
b. 10%
c. 50%
d. 100%
15. ______ is needed for vitamin C
utilization.
a. Acid
b. Iron
c. Phosphorus
d. Calcium
16.The component of blood that
carries oxygen in the body is
a. Fats
b. Myoglobin
c. Hemoglobin
d. Amino acids

17. Most RNA molecules are
a. Independent
b. Double stranded
c. Single stranded
d. Multiple stranded
18.____ are the major components
of soap.
a. Fatty acids
b. Palm oils
c. Proteins
d. Saccharides
19.The mineral, related with the
formation of bones and teeth is.
a. RNA
b. Phosphorus
c. Iron
d. Sulphur

1. What do you understand by the word “Biochemistry”? (21.0.1)
2. Briefly state the functions of carbohydrates. (21.1.4)
3. Name the classes and sub-classes of proteins. (21.2.1)
4. In a range of 0-35º C, the rate of reaction of an enzyme is proportional to
temperature. Justify it. (21.3.2.1)
5. How does pH affect enzyme Activity? (21.3.2.3)
6. Describe lock and key mechanism of enzyme action. (21.3.1.1.1)
7. What is the main use of enzyme in paper industry? (21.3.3)
8. Define co-factors and co-enzymes.
9. Shortly explain the only property that all the lipids have in common.
(21.4.0)
10.Explain the structural components of DNA and RNA. (21.5.1)
2. Give short answers to the following questions

11. Define lipids and state the difference between fat and oil. (21.4.0)
12.Briefly state how vitamin D is formed in human body? (The precursor of
vitamin D3, 7-dehydrocholesterol is produced in relatively large
quantities. 7-Dehydrocholesterol reacts with UVB
light at wavelengths between 270 and 300 nm, with peak synthesis
occurring between 295 and 297 nm.)
13.State the differences between the chemical structures of DNA and RNA.
(21.5.1)
14.Briefly state why minerals are important for human life. (21.6.0)
15. Name different routes for the loss of Zinc from human body. (21.6.1.4.1)
2. Give short answers to the following questions

1. Describe different classes of carbohydrates.
2. Explain the structure of proteins.
3. Briefly describe the factors that affect the Activity of enzymes.
4. What is the nutritional importance of lipids?
5. Explain the structure of nucleic acids.
6. Describe four important minerals and their sources.
3. Give detailed answers to the following questions

21 - Biochemistry
Dr. Hashim Ali
Education (FBISE)
Chemistry F.Sc
II

Chapter 21 biochemistry

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