TOPICS TO BE DISCUSSED
What is biochemistry?
Objectives, scope & importance of biochemistry
and its relation to nutrition.
Lipids: classification of lipids
Metabolism of lipids-
Biosynthesis of fatty acids
Beta oxidation theory with energetic
Ketosis, formation and utilization of ketone bodies.
“Biochemistry has become the foundation for
understanding all biological processes. It has
provided explanations for the causes of many
diseases in humans, animals and plants.”
“Biochemistry is a study of the chemical
substances & processes that occur in plants,
animals & microorganisms & of the changes
they undergo during development & life.”
Biochemistry is both life science and a
chemical science - it explores the
chemistry of living organisms and the
molecular basis for the changes occurring
in living cell.
It uses the methods of chemistry, physics,
molecular biology, and immunology to
study the structure and behavior of the
complex molecules found in biological
material and the ways these molecules
interact to form cells, tissues, and whole
OBJECTIVES OF BIOCHEMISTRY
Study the structures and functions of biomolecules
like carbohydrate, lipids, proteins minerals and
Focuses on techniques used to control diseases,
abnormal deficiency and treatment of deficiencies.
Understand the dynamic changes of cellular
systems and corresponding need of nutrients.
They act as catalyst agent.
Metabolic abnormalities can be studied by
knowledge of biochemistry.
Study of the energy transformations in living cells,
organisms is another objective of study of
IMPORTANCE OF BIOCHEMISTRY
• Biochemistry is thriving right now. In recent years it has
become the most critical area of science.
• It combines the core of biology and chemistry, which
opens a new door for research from the very ground up.
• Biochemistry helps us understand the medical conditions
such as diabetes, jaundice, rickets, etc. with its research,
and scientists are now able to find a medication that can
cure them or put them in control.
• Biochemistry can help us find a way to decompose our
waste without harming nature successfully.
• This field can also do wonders in the coming years and
make us live on other planets as we study the chemical
changes that happen on other planets such as mars.
SCOPES OF BIOCHEMISTRY
Biochemistry play an important role in various fields
such as; in clinical medicine, pharmacology,
biotechnology, agriculture, horticulture, forestry,
nursing, pathology, in physiology, and also in
BIOCHEMISTRY IN MEDICINE
• Nursing and diagnosis
SCOPES OF BIOCHEMISTRY
BIOCHEMISTRY IN AGRICULTURE
• Prevent diseases and Enhance Yield/ growth
SCOPES OF BIOCHEMISTRY
BIOCHEMISTRY IN PHARMACY
• Drug Constitution
• The half-life and Drug storage
• Drug metabolism
• Research Scientist
• Clinical Scientist
• Research Associates
• Chemist Microbiologist
• Biomedical Scientist
• Pharmacologist Laboratory Technician
• Lecturer in an Educational institution
• “Lipids are organic compounds that contain
hydrogen, carbon, and oxygen atoms, which form
the framework for the structure and function of living
These organic compounds are nonpolar molecules,
which are soluble only in nonpolar solvents and
insoluble in water because water is a polar
molecule. In the human body, these molecules can
be synthesized in the liver and are found in oil,
butter, whole milk, cheese, fried foods and also in
some red meats.
Let us have a detailed look at the lipid structure,
properties, types and classification of lipids.
Properties of Lipids
• Lipids are a family of organic
compounds, composed of fats and oils. These
molecules yield high energy and are responsible
for different functions within the human body.
Listed below are some important characteristics
•Lipids are oily or greasy nonpolar molecules,
stored in the adipose tissue of the body.
Lipids are a heterogeneous group of
compounds, mainly composed of hydrocarbon
•Lipids are energy-rich organic molecules,
which provide energy for different life
•Lipids are a class of compounds characterised
by their solubility in nonpolar solvents and
insolubility in water.
•Lipids are significant in biological systems as
they form a mechanical barrier dividing a cell
from the external environment known as the
Lipids are the polymers of fatty acids that contain
a long, non-polar hydrocarbon chain with a small
polar region containing oxygen. The lipid structure
is explained in the diagram below:
Classification of Lipids
Lipids can be classified into two main
• Nonsaponifiable lipids
• Saponifiable lipids
A nonsaponifiable lipid cannot be
disintegrated into smaller molecules
through hydrolysis. Nonsaponifiable lipids
include cholesterol, prostaglandins, etc
• A saponifiable lipid comprises one or more ester
groups, enabling it to undergo hydrolysis in the
presence of a base, acid, or enzymes, including
waxes, triglycerides, sphingolipids and
• Further, these categories can be divided into
non-polar and polar lipids.
• Nonpolar lipids, namely triglycerides, are utilized
as fuel and to store energy.
• Polar lipids, that could form a barrier with an
external water environment, are utilized in
membranes. Polar lipids comprise sphingolipids
• Fatty acids are pivotal components of all these
Types of Lipids
Within these two major classes of lipids, there
are numerous specific types of lipids, which are
important to life, including fatty acids,
triglycerides, glycerophospholipids, sphingolipids
and steroids. These are broadly classified as
simple lipids and complex lipids.
• Esters of fatty acids with various alcohols.
• Fats: Esters of fatty acids with glycerol. Oils are
fats in the liquid state
• Waxes: Esters of fatty acids with higher
molecular weight monohydric alcohols
Esters of fatty acids containing groups in
addition to alcohol and fatty acid.
• Phospholipids: These are lipids containing, in
addition to fatty acids and alcohol, phosphate
group. They frequently have nitrogen-containing
bases and other substituents, eg, in
glycerophospholipids the alcohol is glycerol and
in sphingophospholipids the alcohol is
• Glycolipids (glycosphingolipids): Lipids
containing a fatty acid, sphingosine and
• Other complex lipids: Lipids such as sulfolipids
and amino lipids. Lipoproteins may also be
placed in this category.
Examples of Lipids
There are different types of lipids. Some examples
of lipids include butter, ghee, vegetable oil, cheese,
cholesterol and other steroids, waxes,
phospholipids, and fat-soluble vitamins. All these
compounds have similar features, i.e. insoluble in
water and soluble in organic solvents, etc.
• Waxes are “esters” (an organic compound made
by replacing the hydrogen with acid by an alkyl
or another organic group) formed from long-
alcohols and long-chain carboxylic acids.
• Waxes are found almost everywhere. The fruits
and leaves of many plants possess waxy
coatings, that can safeguard them from small
predators and dehydration.
Membranes are primarily composed of phospholipids that
Triacylglycerols and phosphoacylglycerols are the same,
but, the terminal OH group of the phosphoacylglycerol is
esterified with phosphoric acid in place of fatty acid which
results in the formation of phosphatidic acid.
The name phospholipid is derived from the fact that
phosphoacylglycerols are lipids containing a phosphate
• Our bodies possess chemical messengers
known as hormones, which are basically
organic compounds synthesized in glands and
transported by the bloodstream to various
tissues in order to trigger or hinder the desired
• Steroids are a kind of hormone that is typically
recognized by their tetracyclic skeleton,
composed of three fused six-membered and one
five-membered ring, as seen above. The four
rings are assigned as A, B, C & D as observed in
the shade blue, while the numbers in red
indicate the carbons.
• Fatty acid synthesis is the creation of fatty acids from
acetyl-CoA and NADPH through the action of
enzymes called fatty acid synthases. This process
takes place in the cytoplasm of the cell. Most of the
acetyl-CoA which is converted into fatty acids is
derived from carbohydrates via the glycolytic pathway.
• De novo in Latin means “from the beginning.” Thus,
de novo lipogenesis is the synthesis of fatty acids,
beginning with acetyl-CoA. Acetyl-CoA has to first
move out of the mitochondria, where it is then
converted to Malonyl-CoA (3 carbons).
• Malonyl-CoA then is combined with another acetyl-
CoA to form a 4 carbon fatty acid (1 carbon is given
off as CO2). The addition of 2 carbons is repeated
through a similar process 7 times to produce a 16
carbon fatty acid.
Formation of malonyl COA
Malonyl-CoA is formed by carboxylating acetyl-CoA
using the enzyme acetyl-CoA carboxylase. One
molecule of acetyl-CoA joins with a molecule of
bicarbonate, requiring energy rendered from ATP.
Malonyl-CoA is utilised in fatty acid biosynthesis by
the enzyme Malonyl coenzyme A.
Reaction of fatty acid synthase complex
While the de novo synthesis of fatty acids from
acetyl-CoA occurs in the cytosol on the fatty acid
Fatty acid synthesis is the creation of fatty acids from
acetyl-CoA and NADPH through the action of
enzymes called fatty acid synthases.
FATTY ACID SYNTHESIS PATHWAY
• Acetyl CoA is converted to Malonyl CoA by acetyl
• Malonyl CoA is transferred to FAS.
• Through a series of condensation, reduction, and
dehydration reactions, the two carbons of Malonyl
CoA are added to the growing fatty acyl moiety on
• FAS are then recharged with another Malonyl
moiety, and the cycle continues.
• Each turn of the cycle results in the addition of a
two-carbon group to the fatty acid moiety as well
as the use of one ATP, one acetyl CoA, and two
• When the cycle has completed seven turns, the
16-carbon fatty acid (palmitate) is released from
• Beta oxidation is a metabolic process involving
multiple steps by which fatty acid molecules are
broken down to produce energy.
• More specifically, beta oxidation consists in breaking
down long fatty acids that have been converted to
acyl-CoA chains into progressively smaller fatty acyl-
• This reaction releases acetyl-CoA, FADH2 and NADH,
the three of which then enter another metabolic
process called citric acid cycle or Krebs cycle, in which
ATP is produced to be used as energy.
• Beta oxidation goes on until two acetyl-CoA molecules
are produced and the acyl-CoA chain has been
completely broken down.
• In eukaryotic cells, beta oxidation takes place in the
mitochondria, whereas in prokaryotic cells, it happens
in the cytosol.
Steps of β oxidation
• In the first step, acyl-CoA is oxidized by the
enzyme acyl CoA dehydrogenase. A double bond
is formed between the second and third carbons
(C2 and C3) of the acyl-CoA chain entering the
beta oxidation cycle; the end product of this
reaction is trans-Δ2-enoyl-CoA (trans-delta 2-enoyl
• This step uses FAD and produces FADH2, which
will enter the citric acid cycle and form ATP to be
used as energy. (Notice in the following figure that
the carbon count starts on the right side: the
rightmost carbon below the oxygen atom is C1,
then C2 on the left forming a double bond with C3,
and so on.)
Steps of β oxidation
• In the second step, the double bond between C2
and C3 of trans-Δ2-enoyl-CoA is hydrated, forming
the end product L-β-hydroxyacyl CoA, which has a
hydroxyl group (OH) in C2, in place of the double
• This reaction is catalyzed by another enzyme: enoyl
CoA hydratase. This step requires water.
• In the third step, the hydroxyl group in C2 of L-β-
hydroxyacyl CoA is oxidized by NAD+ in a reaction
that is catalyzed by 3-hydroxyacyl-CoA
• The end products are β-ketoacyl CoA and NADH +
H. NADH will enter the citric acid cycle and produce
ATP that will be used as energy.
• Ketosis is a process that happens when our body
doesn't have enough carbohydrates to burn for energy.
Instead, it burns fat and makes things called ketones,
which it can use for fuel.
• Ketosis is a popular low-carb weight loss program. In
addition to helping you burn fat, ketosis can make you
feel less hungry.
• It also helps you keep muscle. A diet high in fat and
protein but very low in carbs is called a ketogenic or
Formation of ketone bodies
The compounds namely acetone, acetoacetate and β-
hydroxybutyrate (or 3-hydroxy-butyrate) is known as
ketone bodies. Only the first two are true ketones while β-
hydroxybutyrate does not possess a keto (C=O) group.
Ketone bodies are water-soluble and energy yielding.
Acetone, however, is an exception, since it cannot be
The synthesis of ketone bodies occurs in the liver. The enzymes for
ketone body synthesis are located in the mitochondrial matrix.
Acetyl CoA, formed by oxidation of fatty acids, pyruvate or some
amino acids, is the precursor for ketone bodies. Ketogenesis occurs
through the following reactions:
1. Two moles of acetyl CoA condense to form acetoacetyl CoA.
This reaction is catalysed by thiolase, an enzyme involved in the
final step of β-oxidation. Hence, acetoacetate synthesis is
appropriately regarded as the reversal of thiolase reaction of fatty
2. Acetoacetyl CoA combines with another molecule of acetyl CoA
to produce β-hydroxy, β-methyl glutaryl CoA (HMG CoA). HMG
CoA synthase, catalysing this reaction, regulates the synthesis of
3. HMG CoA lyase cleaves HMG CoA to produce acetoacetate and
4. Acetoacetate can undergo spontaneous decarboxylation to form
5. Acetoacetate can be reduced by a dehydrogenase to β-