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Solved 2025: FYUG Even Semester Exam, 2025 Biotechnology (2nd Semester) Cell Biology and Biochemistry (BTCDSM-151)

Time: 3 Hours | Full Marks: 70 | Pass Marks: 28

UNIT-I

Question 1 (Answer any two) 2 x 2 = 4

(a) Differentiate between nucleus and nucleoid.

Feature Nucleus Nucleoid Occurrence Eukaryotic cells Prokaryotic cells Membrane Double-membrane bound No membrane

(b) Point out the components of cell membrane.

  • Phospholipids: Form the basic bilayer structure.
  • Proteins: Peripheral and integral proteins for transport and signaling.
  • Carbohydrates: Attached to lipids or proteins for recognition.
  • Cholesterol: Maintains membrane fluidity.

    • (c) Write a note on cell recognition.

    Cell recognition is the process by which a cell interacts with its environment or other cells by identifying specific molecules on the cell surface

    . This is primarily mediated by glycoproteins and glycolipids that act as molecular "tags" or receptors.

    Question 2 (Answer any one) 10

    Option A

    (a) Give an account of cell theory. Describe the ultrastructure of a prokaryotic cell. 4 + 6 = 10

    Cell Theory:
  • All living organisms are composed of one or more cells.
  • The cell is the basic structural and functional unit of life.
  • All cells arise from pre-existing cells.

    • Ultrastructure of Prokaryotic Cell:
  • Cell Wall: Rigid outer layer made of peptidoglycan.
  • Plasma Membrane: Regulates the entry and exit of substances.
  • Cytoplasm: Contains enzymes and ribosomes.
  • Nucleoid: Region containing the single circular DNA molecule.
  • Ribosomes (70S): Sites of protein synthesis.
  • Flagella/Pili: Used for locomotion and attachment.
    • Option B

    (b) Describe fluid mosaic model of cell membrane with a labelled diagram. Add a note on membrane transport. 7 + 3 = 10

    Fluid Mosaic Model:

    Proposed by Singer and Nicolson, the model describes the membrane as a "mosaic" of proteins floating in or on a "fluid" lipid bilayer

    . The phospholipids provide fluidity, while proteins perform specific functions like transport and enzymatic activity.

    Membrane Transport:
  • Passive Transport: Movement of substances along the concentration gradient without energy (e.g., Diffusion, Osmosis).
  • Active Transport: Movement against the gradient using ATP (e.g., Sodium-Potassium pump).

    • UNIT-II

    Question 3 (Answer any two) 2 x 2 = 4

    (a) Give a short account of vacuoles.

    Vacuoles are membrane-bound sacs used for storage, waste disposal, and maintaining turgor pressure in plant cells

    .

    (b) Write a note on lysosomes.

    Known as "suicide bags," lysosomes contain hydrolytic enzymes that break down macromolecules, old organelles, and foreign substances

    .

    (c) Write briefly about nucleolus.

    The nucleolus is a dense region within the nucleus responsible for the synthesis of ribosomal RNA (rRNA) and the assembly of ribosome subunits

    .

    Question 4 (Answer any one) 10

    Option A

    (a) Describe chloroplast with a labelled diagram. Point out the features of cytoskeleton. 7 + 3 = 10

    Chloroplast: A double-membrane organelle containing thylakoids (stacked into grana) and stroma

    . It is the site of photosynthesis where light energy is converted into chemical energy.

    Cytoskeleton:
  • Composed of Microtubules, Microfilaments, and Intermediate filaments.
  • Provides structural support, maintains cell shape, and assists in organelle movement.
    • Option B

    (b) Give an account of Golgi complex. Add a note on endoplasmic reticulum. 5 + 5 = 10

    Golgi Complex: A series of flattened sacs (cisternae) involved in modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles

    .

    Endoplasmic Reticulum (ER):
  • Rough ER: Studded with ribosomes; involved in protein synthesis.
  • Smooth ER: Lacks ribosomes; involved in lipid synthesis and detoxification.

    • UNIT-III

    Question 5 (Answer any two) 2 x 2 = 4

    (a) Write a note on first prophase of meiosis.

    Prophase I is a complex phase involving Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis

    . It is crucial for crossing over and genetic recombination.

    (b) Define oncogenes.

    Oncogenes are mutated genes that have the potential to cause cancer by promoting uncontrolled cell growth and division.

    (c) Write a note on DNA.

    Deoxyribonucleic acid (DNA) is the hereditary material in organisms, composed of two polynucleotide chains forming a double helix

    .

    Question 6 (Answer any one) 10

    Option A

    (a) Describe Watson-Crick model of DNA. Differentiate between Purines and Pyrimidines. 8 + 2 = 10

    Watson-Crick Model:
  • DNA consists of two helical strands coiled around a common axis.
  • The strands are antiparallel.
  • Bases are on the inside: Adenine pairs with Thymine (A=T); Guanine pairs with Cytosine (G≡C).

    • Differences:
  • Purines: Double-ring structure (Adenine, Guanine).
  • Pyrimidines: Single-ring structure (Cytosine, Thymine, Uracil).

    • UNIT-IV

    Question 7 (Answer any two) 2 x 2 = 4

    (a) Point out the properties of carbohydrates.

    Carbohydrates are optically active, act as reducing agents (reducing sugars), and serve as primary energy sources

    .

    (b) Write a note on forces stabilizing protein structure.

    Structures are stabilized by hydrogen bonds, disulfide bridges, ionic interactions (salt bridges), and hydrophobic interactions

    .

    (c) Write about chemical properties of proteins.

    Proteins exhibit amphoteric behavior, undergo denaturation when heated or exposed to pH changes, and can be hydrolyzed into amino acids

    .

    Question 8 (Answer any one) 10

    Option B

    (b) Give an account of different levels of structural organization of proteins. 10

  • Primary: Linear sequence of amino acids.
  • Secondary: Folding into alpha-helices or beta-sheets via H-bonds.
  • Tertiary: Three-dimensional folding of a single polypeptide.
  • Quaternary: Assembly of multiple polypeptide chains.

    • UNIT-V

    Question 10 (Answer any one) 10

    Option A

    (a) Give an illustrated account of glycolysis. Add a note on cofactors. 7 + 3 = 10

    Glycolysis is a 10-step process occurring in the cytosol where 1 glucose is converted to 2 pyruvate molecules, yielding 2 ATP and 2 NADH

    .

    Cofactors: Non-protein chemical compounds (like Mg2+ or NAD+) required for an enzyme's activity

    .

    Exam Focus Enhancements

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    Exam Tips: In Cell Biology, always draw labeled diagrams for Chloroplast, Mitochondria, and Cell Membrane to secure full marks

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    Common Mistakes: Do not confuse Mitosis (equational) with Meiosis (reductional)

    . Ensure you mention the specific phase names in Prophase I.

    Important Formulas List:

  • Net Yield: C6H12O6 -> 2 Pyruvate + 2 ATP + 2 NADH
  • Chargaff's Rule: A + G = T + C
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    Answer Presentation Strategy: Use tables for differences (e.g., DNA vs RNA or Nucleus vs Nucleoid) as it is highly scannable for examiners

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