(SEM-II) THEORY EXAMINATION, 2019-20 BIOCHEMISTRY

B.Pharm (Sem II) – Biochemistry

Detailed Explanation of Questions and Answers

Biochemistry is the branch of science that studies the chemical reactions and molecular processes that occur within living organisms. It explains how biomolecules such as carbohydrates, proteins, lipids, and nucleic acids interact to sustain life. In pharmacy education, understanding biochemical pathways is essential because many drugs act by modifying these molecular processes. 

Section A – Detailed Answers

Electron Transport Chain

The electron transport chain is a series of protein complexes located in the inner mitochondrial membrane. Its primary function is to transfer electrons from reduced coenzymes such as NADH and FADH₂ to oxygen, which acts as the final electron acceptor.

As electrons move through the chain, energy is released and used to pump protons across the mitochondrial membrane. This creates a proton gradient that drives the synthesis of ATP through oxidative phosphorylation.

This process is essential for producing energy required for cellular activities.

Free Energy

Free energy refers to the amount of energy in a system that is available to perform useful work. In biological systems, the concept of free energy is described by Gibbs free energy.

Reactions that release free energy are known as exergonic reactions, while those that require energy input are called endergonic reactions.

Cells use energy stored in molecules such as ATP to drive biochemical reactions necessary for metabolism.

Hyperbilirubinemia

Hyperbilirubinemia is a condition characterized by elevated levels of bilirubin in the blood. Bilirubin is produced during the breakdown of hemoglobin from old red blood cells.

When bilirubin accumulates in the body due to liver dysfunction or excessive red blood cell destruction, it leads to yellow discoloration of the skin and eyes.

This condition is commonly associated with jaundice.

Redox Potential

Redox potential refers to the tendency of a chemical substance to acquire or donate electrons during oxidation-reduction reactions.

In biochemical systems, redox reactions play a vital role in metabolic pathways such as cellular respiration and photosynthesis.

Electron carriers such as NAD⁺ and FAD participate in these reactions to facilitate energy production.

Jaundice

Jaundice is a medical condition characterized by yellow discoloration of the skin, eyes, and mucous membranes. It occurs due to accumulation of bilirubin in the blood.

The condition may result from liver diseases, excessive breakdown of red blood cells, or obstruction of bile ducts.

Vitamin D

Vitamin D is a fat-soluble vitamin that plays a crucial role in maintaining calcium and phosphorus balance in the body.

It promotes absorption of calcium from the intestine and supports healthy bone formation. Deficiency of vitamin D can lead to diseases such as rickets in children and osteomalacia in adults.

Full Forms of Biochemical Abbreviations

Several biochemical molecules are commonly abbreviated in metabolic pathways.

NADH stands for Nicotinamide Adenine Dinucleotide (reduced form).
ATP stands for Adenosine Triphosphate.
TPP stands for Thiamine Pyrophosphate.
UDP stands for Uridine Diphosphate.
UTP stands for Uridine Triphosphate.
NADPH stands for Nicotinamide Adenine Dinucleotide Phosphate (reduced form).

These molecules function as coenzymes or energy carriers in biochemical reactions.

Gout

Gout is a metabolic disorder characterized by excessive accumulation of uric acid in the blood.

When uric acid levels become too high, crystals of urate may deposit in joints, leading to inflammation and severe pain.

This condition is often associated with disorders of purine metabolism.

Structure of ATP

ATP, or adenosine triphosphate, is the primary energy currency of the cell.

It consists of an adenine base attached to a ribose sugar and three phosphate groups. The bonds between the phosphate groups store large amounts of energy.

When ATP is hydrolyzed to ADP, energy is released that can be used for various cellular processes.

Cholesterol

Cholesterol is a sterol lipid found in cell membranes of animal cells. It plays an important role in maintaining membrane fluidity and stability.

Cholesterol also serves as a precursor for the synthesis of steroid hormones, bile acids, and vitamin D.

Section B – Detailed Explanation

Classification of Proteins

Proteins are large biomolecules composed of amino acids linked together by peptide bonds. They perform numerous functions in the body, including structural support, enzymatic activity, and transport of molecules.

Proteins can be classified into simple proteins and conjugated proteins. Simple proteins consist only of amino acids, while conjugated proteins contain additional non-protein components known as prosthetic groups.

Examples include hemoglobin and lipoproteins.

Glycolysis Pathway

Glycolysis is the metabolic pathway that converts glucose into pyruvate while producing energy.

This process occurs in the cytoplasm and consists of ten enzymatic reactions. During glycolysis, glucose is broken down into two molecules of pyruvate.

The pathway generates ATP and NADH, which are used in subsequent stages of cellular respiration to produce additional energy.

Lipids and Their Classification

Lipids are hydrophobic biomolecules that include fats, oils, phospholipids, and sterols.

They serve as energy storage molecules, structural components of cell membranes, and precursors for signaling molecules.

Lipids can be classified into simple lipids, compound lipids, and derived lipids.

Section C – Detailed Explanation

Enzyme Kinetics and Properties of Enzymes

Enzyme kinetics studies the rate of enzyme-catalyzed reactions and how factors such as substrate concentration, temperature, and pH influence reaction speed.

Enzymes possess several properties such as high specificity, catalytic efficiency, and sensitivity to environmental conditions.

They function by lowering the activation energy required for chemical reactions.

Structure of DNA and RNA

DNA and RNA are nucleic acids responsible for storing and transmitting genetic information.

DNA consists of two complementary strands forming a double helix structure. Each strand contains nucleotides composed of a sugar, phosphate group, and nitrogenous base.

RNA is usually single-stranded and plays a role in protein synthesis.

Conversion of Cholesterol into Bile Acids

Cholesterol is converted into bile acids in the liver through a series of enzymatic reactions.

Bile acids help emulsify fats in the digestive tract, allowing digestive enzymes to break down lipids more effectively.

They also aid in the absorption of fat-soluble vitamins.

Genetic Code and Hypercholesterolemia

The genetic code is the system by which sequences of nucleotides in DNA determine the sequence of amino acids in proteins.

Hypercholesterolemia refers to abnormally high levels of cholesterol in the blood, which increases the risk of cardiovascular diseases.

Coenzymes

Coenzymes are small organic molecules that assist enzymes in catalyzing biochemical reactions.

Examples include NAD⁺, FAD, and coenzyme A. These molecules act as carriers of electrons, atoms, or functional groups during metabolic reactions.

Glycogen Metabolism

Glycogen metabolism involves the synthesis and breakdown of glycogen, the storage form of glucose in animals.

Glycogen synthesis occurs when excess glucose is converted into glycogen for storage in the liver and muscles.

During fasting or increased energy demand, glycogen is broken down into glucose through glycogenolysis.

Ketone Body Formation and Utilization

Ketone bodies are produced in the liver from fatty acids during periods of fasting or carbohydrate deficiency.

The main ketone bodies include acetoacetate, beta-hydroxybutyrate, and acetone.

These molecules serve as alternative energy sources for tissues such as the brain and muscles when glucose availability is limited.

Conclusion

Biochemistry provides a detailed understanding of metabolic processes that sustain life. Knowledge of pathways such as glycolysis, glycogen metabolism, and oxidative phosphorylation helps explain how the body produces energy and maintains biochemical balance.

For pharmacy students, understanding these pathways is essential for understanding drug action and disease mechanisms.