BIOTECHNOLOGY: Biochemistry (BTCDSC-151T)
FYUG Even Semester Exam, 2024

Course No: BTCDSC-151T | Full Marks: 70 | Pass Marks: 28

Subject: Biotechnology

Paper Name: Biochemistry

Semester: 2nd Semester

Exam Year: 2024

SECTION-A (Answer any ten) 2 × 10 = 20 Marks

1. What is amino acid? Write about peptide bond.

An amino acid is an organic molecule containing both an amino group (-NH2) and a carboxyl group (-COOH), serving as the building block of proteins. A peptide bond is a covalent chemical bond formed between the carboxyl group of one amino acid and the amino group of another, releasing a molecule of water.

2. Write about fibrous and globular protein.

3. Write down the physical properties of proteins.

Physical properties of proteins include solubility (varies with pH and salt concentration), viscosity, optical activity, and denaturation (loss of structure due to heat or chemicals).

4. Define monosaccharides. Draw the structure of glucose.

Monosaccharides are the simplest form of carbohydrates that cannot be hydrolyzed into smaller units. They are the basic units (monomers) of all sugars.

Structure of Glucose (C6H12O6):

CHO — CHOH — CHOH — CHOH — CHOH — CH2OH

5. Write down the function of monosaccharides.

  • Act as the primary energy source for cells (e.g., Glucose).
  • Serve as building blocks for complex carbohydrates like starch and cellulose.
  • Component of nucleic acids (e.g., Ribose in RNA).

6. What is mucopolysaccharide?

Mucopolysaccharides (also known as Glycosaminoglycans) are long chains of sugar molecules found throughout the body, often in mucus and in fluid around the joints. They provide structural support and lubrication.

7. Define fatty acid.

A fatty acid is a carboxylic acid with a long aliphatic chain, which is either saturated or unsaturated. They are key components of lipids.

8. What is steroid?

A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration. Examples include cholesterol and various hormones like testosterone.

9. Write a note on purines and pyrimidines.

Purines (Adenine, Guanine) are nitrogenous bases with a double-ring structure, while Pyrimidines (Cytosine, Thymine, Uracil) have a single-ring structure. They are the essential components of nucleotides in DNA and RNA.

10. Define active site of an enzyme.

The active site is a specific region of an enzyme where substrate molecules bind and undergo a chemical reaction. It is usually a small pocket or cleft on the enzyme's surface.

11. What is cofactor?

A cofactor is a non-protein chemical compound or metallic ion that is required for an enzyme's activity as a catalyst.

12. Write a note on lock-and-key model.

The lock-and-key model, proposed by Emil Fischer, suggests that the enzyme and substrate possess specific complementary geometric shapes that fit exactly into one another.

13. What is the fate of pyruvate under aerobic and anaerobic condition?

  • Aerobic: Pyruvate enters the mitochondria and is converted into Acetyl-CoA to enter the TCA cycle.
  • Anaerobic: In animals, pyruvate is reduced to Lactate; in yeast, it is converted to Ethanol and CO2.

14. What is TCA cycle?

The TCA (Tricarboxylic Acid) cycle, or Krebs cycle, is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.

15. Write a note on gluconeogenesis.

Gluconeogenesis is a metabolic pathway that results in the generation of glucose from certain non-carbohydrate carbon substrates like pyruvate, lactate, and glycerol.

SECTION-B (Answer any five) 10 × 5 = 50 Marks

16. Describe the different levels of structural organization of proteins. Forces stabilizing protein structure.

Proteins have four distinct levels of structure:

  1. Primary Structure: The linear sequence of amino acids in a polypeptide chain.
  2. Secondary Structure: Local folding into patterns like Alpha-helices and Beta-sheets, stabilized by hydrogen bonds.
  3. Tertiary Structure: The overall three-dimensional shape of a single protein molecule, resulting from R-group interactions.
  4. Quaternary Structure: The arrangement of multiple folded protein subunits in a multi-subunit complex.

Stabilizing Forces: Hydrogen bonds, Ionic bonds (salt bridges), Hydrophobic interactions, and Disulfide bridges (covalent).

20. What are essential and non-essential fatty acids? Add a note on phospholipid and glycolipid.

  • Essential Fatty Acids: Those that cannot be synthesized by the body and must be obtained from the diet (e.g., Linoleic acid).
  • Non-essential Fatty Acids: Those that can be synthesized by the body from other nutrients.

Phospholipids: Lipids containing a phosphate group, forming the primary component of cell membranes (lipid bilayer).

Glycolipids: Lipids with a carbohydrate attached by a glycosidic bond, important for cell recognition and signaling on the cell surface.

21. Describe the structure of DNA. Add a note on properties of nucleic acids.

DNA Structure: DNA exists as a double helix of two antiparallel polynucleotide chains. Each nucleotide consists of a deoxyribose sugar, a phosphate group, and a nitrogenous base (A, T, C, G). Bases pair specifically (A=T and C≡G) via hydrogen bonds.

Properties of Nucleic Acids: They exhibit UV absorption (at 260 nm), denaturation (melting) when heated, and hybridization capability.

22. Nomenclature and classification of enzymes. Add a note on enzyme inhibition.

Enzymes are classified into six major classes by the IUBMB:

  1. Oxidoreductases: Catalyze oxidation-reduction reactions.
  2. Transferases: Transfer functional groups.
  3. Hydrolases: Catalyze hydrolysis.
  4. Lyases: Add or remove groups to form double bonds.
  5. Isomerases: Catalyze structural shifts (isomers).
  6. Ligases: Join two molecules using ATP.

Enzyme Inhibition: This involves molecules (inhibitors) that decrease enzyme activity. It can be Competitive (binds to active site) or Non-competitive (binds elsewhere).

24. Describe the steps of glycolysis. Add a note on glycogenolysis.

Glycolysis: A 10-step pathway that converts one molecule of glucose into two molecules of pyruvate, generating a net of 2 ATP and 2 NADH.

  • Preparatory Phase: Glucose is phosphorylated and cleaved into two 3-carbon units (requires 2 ATP).
  • Pay-off Phase: Oxidation and phosphorylation produce 4 ATP and 2 NADH.

Glycogenolysis: The biochemical breakdown of glycogen into glucose-1-phosphate and glucose to maintain blood sugar levels during fasting or exercise.

Exam Focus Enhancements

  • Exam Tips: Always mention the antiparallel nature when describing DNA. In metabolic pathways, highlight the rate-limiting enzymes (e.g., PFK-1 in glycolysis).
  • Common Mistakes: Don't confuse Gluconeogenesis (making glucose) with Glycogenolysis (breaking down glycogen).
  • Important Formulas: Net Reaction of Glycolysis: Glucose + 2NAD+ + 2ADP + 2Pi → 2 Pyruvate + 2NADH + 2H+ + 2ATP + 2H2O.
  • Strategy: In 10-mark questions like Q22, list all 6 classes of enzymes for full credit.

© 2026 Knowlet | Academic Excellence