2. INTRODUCING CARBOHYDRATES
Carbohydrates are a group of substances used as both
energy sources and structural materials in organisms.
All carbohydrates contain carbon, hydrogen and oxygen,
with the general formula: Cx(H2O)y.
There are three main groups of carbohydrates:
monosaccharides – these are simple sugars, with the
general formula (CH20)n, where n can be 3–7
disaccharides – these are ‘double sugars’, formed from
two monosaccharides
polysaccharides – these are large molecules formed
from many monosaccharides.
3. GLUCOSE
The structure of glucose can be represented in different ways:
Glucose is an abundant and very important monosaccharide.
It contains six carbon atoms so it is a hexose sugar. Its
general formula is C6H12O6.
Glucose is the major energy source for most cells. It is highly
soluble and is the main form in which carbohydrates are
transported around the body of animals.
straight chain ring ring (simplified)
4. GLUCOSE
• Glucose is an abundant and very important monosaccharide. It
contains six carbon atoms so it is a hexose sugar. Its general formula is
C6H12O6.
• Glucose is the major energy source for most cells. It is highly soluble
and is the main form in which carbohydrates are transported around
the body of animals.
• The structure of glucose can be represented in different ways:
straight chain
ring ring (simplified)
5. ALPHA AND BETA GLUCOSE
Glucose exists in different forms called structural isomers.
Two common isomers are alpha glucose and beta glucose.
alpha
glucose
beta
glucose
The only difference between these two isomers is the position
of the –OH group attached to carbon 1. In alpha glucose it is
below the carbon and in beta glucose it is above the carbon.
1
2
3
4
5
6
1
2
3
4
5
6
This minor structural difference has a major effect on the
biological roles of alpha and beta glucose.
6. FRUCTOSE AND GALACTOSE
Galactose is not as soluble as glucose and has an important
role in the production of glycolipids and glycoproteins.
Two other important hexose monosaccharides are fructose
and galactose.
fructose galactose
Fructose is very soluble and is the main sugar in fruits and
nectar. It is sweeter than glucose.
7. PENTOSES
Pentose monosaccharides contain five carbon atoms. Like
hexoses, pentoses are long enough to form a ring.
Two important pentose molecules are the structural isomers
ribose and deoxyribose. These are important constituents
of RNA and DNA.
ribose deoxyribose
The only difference between them is that ribose has one
H atom and one –OH group attached to carbon 2,
whereas deoxyribose has 2 H atoms and no –OH group.
1
2
3
4
5
1
2
3
4
5
9. MALTOSE, SUCROSE AND LACTOSE
Maltose (malt sugar) is
formed from two glucose
molecules joined by an
alpha 1–4 glycosidic bond.
Sucrose (table sugar) is
formed from glucose and
fructose joined by an alpha
1–4 glycosidic bond.
Lactose (milk sugar) is
formed from galactose and
glucose joined by a beta 1–
4 glycosidic bond.
13. PROPERTIES AND USES OF STARCH
Starch is the major carbohydrate storage molecule in plants.
Starch is produced from glucose made during photosynthesis.
It is broken down during respiration to provide energy and is
also a source of carbon for producing other molecules.
It is usually stored as
intracellular starch
grains in organelles
called plastids.
Plastids include green
chloroplasts (e.g. in
leaves) and colourless
amyloplasts (e.g. in
potatoes).
15. WHAT IS CELLULOSE?
Unlike starch, cellulose is very strong, and prevents cells
from bursting when they take in excess water.
Cellulose is another polysaccharide and is the main part of
plant cell walls. It is the most abundant organic polymer.
Cellulose consists of long
chains of beta glucose
molecules joined by beta
1–4 glycosidic bonds.
The glucose chains form
rope-like microfibrils,
which are layered to form
a network.
17. WHAT IS GLYCOGEN?
Animals do not store carbohydrate as starch but as glycogen.
Glycogen has a similar
structure to amylopectin,
containing many alpha 1–6
glycosidic bonds that produce an
even more branched structure.
Glycogen is less dense and more soluble than starch, and is
broken down more rapidly. This indicates the higher
metabolic requirements of animals compared with plants.
Glycogen is stored as small
granules, particularly in
muscles and liver.
19. CARBOHYDRATES
• All carbohydrates contain
carbon, hydrogen and
oxygen
• There are two types of
carbohydrates i) SIMPLE
ii) COMPLEX
• Simple sugar is GLUCOSE.
• The glucose can be
represented in the cyclic or
linear form as shown below.
35. • GLYCOGEN- It forms food storage form in animal cells
• STARCH- It is made up of hundreds of glucose molecules joined
together to form long chains
• Starch is the important storage substances in the plastid of plant cells
• Cellulose consists of even longer chains of glucose molecules.
• Chain molecules are grouped together to form microscopic fibres which are
laid down in layers to form the cell wall in plant cells.
• Polysaccharides are not readily soluble in water
36. FUNCTIONS OF CARBOHYDRATES
• Energy giving foods (1gm – 17kj energy)
• Glucose used in respiration
• Blood plasma transports glucose to all the cells
• PLANTS produce glucose during photosynthesis
• Transport SUCROSE to the parts of the plant that needs it
• Stores excess glucose as STARCH
• CELLULOSE is used in making plant cells
• ANIMALS store excess glucose as GLYCOGEN in the liver and muscles
38. INTRODUCTION TO LIPIDS
Lipids are a diverse group of compounds that are insoluble in
water but soluble in organic solvents such as ethanol.
The most common types of lipid
are triglycerides (sometimes
known as true fats or neutral
fats), but other important lipids
include waxes, steroids and
cholesterol.
Like carbohydrates, lipids contain carbon, hydrogen and oxygen, but
they have a higher proportion of hydrogen and a lower proportion of
41. ROLE OF LIPIDS
• The major biological role of lipids is as an
energy source. Lipids provide more than
twice the amount of energy as carbohydrates
– about 38 kJ/g.
• Lipids are stored in adipose tissue, which
has several important roles, including:
• heat insulation – in mammals, adipose tissue
underneath the skin helps reduce heat loss.
• protection – adipose tissue around delicate
organs such as the kidneys acts as a
cushion against impacts.
45. FATS
• Are known as TRIGLYCERIDES
• Fats are a solid form a group of molecules called LIPIDS.
• When lipids are liquids they are known as OILS.
• Fats and oils are formed from carbon, hydrogen and oxygen only.
• Made up of one GLYCEROL molecule joined to three FATTY ACIDS
46. FATTY ACIDS
• Fatty acids are carboxylic acids, that is, they possess a
COOH (functional) group attached to a hydrocarbon chain.
• They come in three basic forms: SATURATED, MONOUNSATURATED AND
POLYUNSATURATED.
• A SATURATED FATTY ACID has no double bonds between any of the carbon atoms
that make up the hydrocarbon chain.
• A MONOUNSATURATED FATTY ACID has a single double bond and, logically, a
POLYUNSATURATED FATTY ACID has two or more double bonds in its hydrocarbon
chain.
• A UNSATURATED FATTY ACIDS can be either cis or trans isomers depending on the
position of the two hydrogen atoms around the carbon–carbon double bond
47.
48.
49.
50.
51. LIPID TRANSPORT
• Lipids are not soluble in water
• This means they cannot be dissolved in blood plasma & carried
around the body in the same manner as glucose
• Triglycerides are broken down into fatty acids and glycerol
i. Glycerol dissolves in the blood plasma
ii. Fatty acids combines with the plasma proteins and carried in the
blood as globules
52. FUNCTIONS OF FATS
• Fats and oils can be used in a cell to release energy
• A gram of fat gives 39KJ of energy
• Most cells use fats when An all the available carbohydrates have
been used.
1) INSULATION AND PADDING:
• Fats are deposited in adipose tissue, subcutaneous tissue and
abdominal cavity
• Fats surrounds the organs and laced throughout muscle tissue
• Fats functions like insulating material against cold
• Fats protects vital organs against physical injuries by forming a
padding around them
53. FUNCTIONS OF FATS
2) Energy:
• The primary function of fat is to supply energy.
• It is a very concentrated source of energy.
• Each gram of fat when oxidized yields approximately 39 kJ, twice as much energy as one
gram of carbohydrate or protein.
• Fat specially supply energy in between the meals and during starvation.
3) SATEITY FUNCTION
• Fats improves the palatability of the diet.
• It slows digestion--resulting in satiety (a sense of fullness and satisfaction after eating.
• Fats provide essential fatty acids which the body can’t manufacture.
• Fats are the constituents of cell membrane and regulates the membrane permeability.
55. Glycogenesis, glycogenolysis, and gluconeogenesis
• GLYCOGENESIS- is the formation of glycogen from glucose.
• GLYCOGENOLYSIS- Glycogen stored in the liver and muscles, is converted first to
glucose-1- phosphate and then into glucose-6-phosphate. Two hormones which
control glycogenolysis are a peptide, glucagon from the pancreas and epinephrine
from the adrenal glands.
• GLUCONEOGENESIS is the process of synthesizing glucose from non-
carbohydrate sources.
• GLYCOLYSIS- is the breakdown of glucose into pyruvate
56. INTRODUCING PROTEINS
• Proteins are a diverse group of large and complex polymer
molecules, made up of long chains of amino acids.
• They have a wide range of biological roles, including:
• structural: proteins are the main component of body tissues,
such as muscle, skin, ligaments and hair
• catalytic: all enzymes are proteins, catalyzing many
biochemical reactions
• signalling: many hormones and receptors are proteins
• immunological: all antibodies are proteins.
58. THE GENERAL STRUCTURE OF AMINO ACIDS
All amino acids have the same general structure: the only difference
between each one is the nature of the R group. The R group
therefore defines an amino acid.
amino
group
carboxylic acid
group
R group
The R group represents a side chain from the central ‘alpha’ carbon
atom, and can be anything from a simple hydrogen atom to a more
complex ring structure.
63. POLYPEPTIDES
When more amino acids are
added to a dipeptide, a
polypeptide chain is formed.
A protein consists of one or
more polypeptide chains folded
into a highly specific 3D shape.
There are up to four levels of structure in a protein: primary, secondary,
tertiary and quaternary. Each of these play an important role in the overall
structure and function of the protein.
66. BONDS IN PROTEINS
The 3D shape of a protein is maintained by several types of bond,
including:
hydrogen bonds:
involved in all levels of structure.
hydrophobic interactions:
between non-polar sections of
the protein.
disulfide bonds: one of the strongest
and most important type of bond in
proteins. Occur between two
cysteine amino acids.
67. FIBROUS PROTEINS
Fibrous proteins are formed from parallel polypeptide chains held
together by cross-links. These form long, rope-like fibres, with high
tensile strength and are generally insoluble in water.
collagen – the main component
of connective tissue such as
ligaments, tendons,
cartilage.
keratin – the main component
of hard structures such as
hair, nails, claws and hooves.
silk – forms spiders’ webs and silkworms’ cocoons.
68. Globular proteins usually have a spherical shape caused by tightly
folded polypeptide chains.
The chains are usually folded so that hydrophobic groups are on the
inside, while the hydrophilic groups are on the outside. This makes
many globular proteins soluble in water.
enzymes – such as lipase and
DNA polymerase.
hormones – such as oestrogen
and insulin.
transport proteins – such as
haemoglobin, myoglobin and
those embedded in membranes.
GLOBULAR PROTEINS
70. GLOBULAR PROTEIN HAEMOGLOBIN
• It has quaternary structure of 4
polypeptide chains: 2 identical alpha
chain of 141 amino acids and 2 identical
beta chains of 146 amino acids chain
• Each polypeptide is folded into compact
shape and are linked together to form
spherical shape
• Hydrophobic interactions with non polar
group within Hg helps in maintaining the
shape- Imp. Factor in its ability to carry
oxygen.
71. GLOBULAR PROTEIN HAEMOGLOBIN
• Amino acids with hydrophilic R group tends to
point outwards which enable the Hg to mix
readily with the water part of the blood
• Prosthetic group and conjugated protein
• Each Fe2+ combine with single O2 making
total of 4 O2 molecules that can be carried
by single Hg in humans
• When oxygen combines with haemoglobin it
forms oxyhemoglobin and changes color from
purple to bright red.
72. FIBROUS PROTEIN
• Fibrous protein tend to form long chain and run parallel to each other
• Chains are linked by cross bridges and form stable molecules
• Collagen found in tissues requiring physical strength
• Collagen is extremely strong and has high tensile strength & can
withstand immense pulling forces without stretching.
• It can bend around the joint as it flexes during the movement.
• Tendons is an example of fibrous protein
73. COLLAGEN
• Primary structure is repeat of glycine-proline-alanine forms unbranched
polypeptide
• Made of 3 polypeptide wound in a triple helix held together by hydrogen bonds
between peptide bond NH of glycine and CO bonds of adjacent polypeptide
• As every third amino acid is the small and compact glycine molecule, the triple
helix produced are tightly wound. Larger aminoacid produce loosely wound and
thus less strong
• The triple stranded molecules forms even stronger units called FIBRILS
• Collagen molecules in the collagen fibers are held together by cross linkages
formed by covalent bonds between lysine amino acids of adjacent molecules.
74. • The point where one collagen molecule ends
and next begins are spread throughout the
structure. If they were all joined together in
the same region this would be a weak point &
prone to breaking under tension.
75. PROTEINS
• Antibodies are proteins produced by white blood cells called LYMPHOCYTES
• Each antibody has a binding site, which can lock onto pathogens such as bacteria
• This destroys bacteria directly, or marks it so that it can be detected by other WBC
called PHAGOCYTES
• Each pathogen ANTIGENS on its surface that are particular shape, so specific
antibodies with complementary shape to the antigens.
• When protein is heated to temp over 50ºC it will lost its shape & gets denatured
• Egg white is a protein Albumen. When its heated, its molecules change its shape &
goes from clear liquid to white solid.
76. FUNCTION OF PROTEINS
• They are used to make new cells which are needed for growing and for
repairing damaged parts of the body.
• Cell membranes and cytoplasm contains lots of protein
• Proteins are needed to make antibodies which fight against bacteria and
viruses inside the body.
• Plants use some of carbohydrates to make proteins.
• To do this, they need ammonium or nitrate ions. These ion contain
nitrogen which combine with carbohydrates to make amino acids.
• The amino acids are linked into long chain to make a protein
79. STRUCTURE OF WATER
Each hydrogen shares a pair of
electrons with the oxygen. The oxygen
has a greater affinity for electrons than
the hydrogens, so it ‘pulls’ the
electrons closer.
Water (H2O) consists of two
hydrogen atoms covalently bonded
to one oxygen atom.
This makes the oxygen slightly negative (indicated by δ–)
and the hydrogens slightly positive (indicated by δ+).
This creates different charged regions, making water a polar
molecule. Because it has two charged regions it is dipolar.
104.5°
δ–
δ+
δ+
80. HYDROGEN BONDS
The slight negative charge on the oxygen atom makes it
attract the slightly positive hydrogen atom of another water
molecule.
Many of the properties of water are due to its ability to form
hydrogen bonds.
The numerous hydrogen bonds in water make it a very
stable structure.
hydrogen
bond
83. What is bulk transport?
When extremely large substances need to be moved across
a cell membrane, bulk transport is used.
Endocytosis is the bulk transport
of material in to the cell, and can
be split into three processes:
phagocytosis, pinocytosis and
receptor-mediated endocytosis.
Exocytosis is the bulk transport of material out of the
cell – essentially the reverse of endocytosis.
The two types of bulk transport are
endocytosis and exocytosis, and they
involve changes to the membrane shape.
