CSIR NET Life Sciences Cellular Organization Syllabus

Cellular Organization syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Cellular Organization in CSIR NET Life Sciences, not a summary of it.

1. 1

   Membrane structure and function

   8 topics

   • Structure of model membrane
   • Lipid bilayer and membrane protein diffusion
   • Osmosis
   • Ion channels
   • Active transport
   • Membrane pumps
   • Mechanism of sorting and regulation of intracellular transport
   • Electrical properties of membranes
2. 2

   Structural organization and function of intracellular organelles

   11 topics

   • Cell wall
   • Nucleus
   • Mitochondria
   • Golgi bodies
   • Lysosomes
   • Endoplasmic reticulum
   • Peroxisomes
   • Plastids
   • Vacuoles
   • Chloroplast
   • Structure & function of cytoskeleton and its role in motility
3. 3

   Organization of genes and chromosomes

   5 topics

   • Operon
   • Unique and repetitive DNA
   • Interrupted genes
   • Gene families
   • Structure of chromatin and chromosomes
     • Heterochromatin
     • Euchromatin
     • Transposons
4. 4

   Cell division and cell cycle

   4 topics

   • Mitosis and meiosis
   • Regulation of mitosis and meiosis
   • Steps in cell cycle
   • Regulation and control of cell cycle
5. 5

   Microbial Physiology

   3 topics

   • Growth yield and characteristics
   • Strategies of cell division
   • Stress response

Cellular Organization flashcards for CSIR NET Life Sciences

25 of 53 cards from the Cellular Organization deck — real questions with worked answers.

1. What does the fluid mosaic model (Singer-Nicolson, 1972) propose about membrane structure?

   The membrane is a two-dimensional fluid of a phospholipid bilayer in which globular proteins are embedded (integral) or attached (peripheral) and can diffuse laterally; lipids and proteins form a dynamic 'mosaic'.

2. What are the main types of lipids found in a biological membrane?

   Phospholipids (glycerophospholipids), sphingolipids, glycolipids, and cholesterol (sterols).

3. How does cholesterol affect membrane fluidity at high vs low temperatures?

   It is a fluidity buffer: at high temperatures it restrains phospholipid movement (reduces fluidity), while at low temperatures it prevents tight packing (maintains fluidity, lowers transition temperature).

4. Which type of lipid movement is rare and requires the enzyme flippase?

   Transverse (flip-flop) movement of a lipid from one leaflet to the other; it is energetically unfavorable and catalyzed by flippases (ATP-dependent).

5. Compare lateral diffusion and flip-flop diffusion rates of membrane lipids.

   Lateral diffusion is very fast (a lipid can move ~1 µm in seconds), whereas flip-flop (transverse) diffusion is extremely slow (occurs over hours/days without enzymes).

6. What experiment demonstrated lateral mobility of membrane proteins?

   The Frye-Edidin cell fusion experiment (1970): fusing mouse and human cells labeled with different fluorescent antibodies showed intermixing of surface proteins, proving lateral diffusion.

7. Differentiate integral and peripheral membrane proteins.

   Integral proteins are embedded in/span the bilayer via hydrophobic interactions and need detergents to remove; peripheral proteins are loosely bound to the surface via electrostatic/H-bonds and can be removed by mild salt/pH changes.

8. Define osmosis.

   The net movement of water (solvent) across a semipermeable membrane from a region of lower solute concentration (higher water potential) to higher solute concentration (lower water potential).

9. Define tonicity and the three tonicity conditions for a cell.

   Tonicity is the ability of a solution to change cell volume. Hypotonic: cell gains water and swells; Hypertonic: cell loses water and shrinks (crenation/plasmolysis); Isotonic: no net water movement.

10. Which water channel proteins greatly increase the rate of osmosis across membranes?

    Aquaporins.

11. Distinguish voltage-gated, ligand-gated, and mechanically-gated ion channels.

    Voltage-gated open in response to membrane potential changes; ligand-gated open when a chemical (e.g., neurotransmitter) binds; mechanically-gated open in response to physical deformation/stretch.

12. What is the selectivity filter of the K+ channel and how does it select K+ over Na+?

    A narrow pore lined by backbone carbonyl oxygens (signature TVGYG motif) that mimic the hydration shell of K+; it dehydrates and conducts K+ but the smaller Na+ cannot be coordinated optimally, so it is excluded.

13. Differentiate primary and secondary active transport.

    Primary active transport directly uses ATP hydrolysis to move solutes against a gradient (e.g., Na+/K+ ATPase); secondary active transport uses the electrochemical gradient set up by primary transport (e.g., Na+-glucose symport).

14. Differentiate symport, antiport, and uniport.

    Uniport moves one solute in one direction; symport (cotransport) moves two solutes in the same direction; antiport (exchange) moves two solutes in opposite directions.

15. Describe the stoichiometry and effect of the Na+/K+ ATPase.

    For each ATP hydrolyzed it pumps 3 Na+ out and 2 K+ in against their gradients; it is electrogenic, maintaining low intracellular Na+, high K+, and contributing to the resting membrane potential.

16. What are the four classes of ATP-driven membrane pumps?

    P-type ATPases (phosphorylated intermediate, e.g., Na+/K+, Ca2+ pump), V-type (acidify vacuoles/lysosomes), F-type (ATP synthase, runs in reverse), and ABC transporters (use ATP to pump small molecules).

17. What is the function of the SERCA pump?

    SERCA (Sarco/Endoplasmic Reticulum Ca2+-ATPase) is a P-type pump that transports Ca2+ from the cytosol into the ER/SR lumen, keeping cytosolic Ca2+ low.

18. What sorting signal directs proteins into the ER lumen and which signal retains them there?

    An N-terminal signal sequence (hydrophobic) directs cotranslational entry into the ER; the C-terminal KDEL sequence retains soluble proteins in the ER lumen (retrieved from Golgi).

19. Which coat proteins mediate anterograde and retrograde vesicle transport between ER and Golgi?

    COPII coats vesicles moving anterograde (ER → Golgi); COPI coats vesicles moving retrograde (Golgi → ER); clathrin coats vesicles from the trans-Golgi/plasma membrane.

20. What is the role of SNARE proteins in intracellular transport?

    v-SNAREs on the vesicle pair with t-SNAREs on the target membrane to mediate specific docking and fusion of the transport vesicle with its target compartment.

21. What signal targets enzymes to the lysosome and where is it added?

    Mannose-6-phosphate (M6P), added in the cis-Golgi; M6P receptors in the trans-Golgi network sort the enzymes into clathrin-coated vesicles destined for lysosomes.

22. What is the resting membrane potential and roughly what value does a typical neuron have?

    The voltage difference across the membrane at rest (inside negative), about -70 mV in a typical neuron, set mainly by K+ permeability and the Na+/K+ pump.

23. State the Nernst equation purpose and write it for an ion at 37°C.

    It gives the equilibrium potential of a single ion. E_ion = (61.5/z) log([ion]out/[ion]in) mV at 37°C, where z is the ion's charge.

24. What does the Goldman-Hodgkin-Katz equation calculate?

    The resting membrane potential accounting for the relative permeabilities and concentrations of multiple ions (mainly K+, Na+, Cl-) simultaneously.

25. What is the chemical composition of the plant cell wall vs the bacterial cell wall?

    Plant cell wall: cellulose microfibrils with hemicellulose, pectin, and lignin; bacterial cell wall: peptidoglycan (murein, NAG-NAM chains cross-linked by peptides).

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