Exam questions

Cell Biology Exam Practice Notes

1. FRAP Experiment and Fluorescence Recovery

  • Question: A FRAP experiment shows very slow fluorescence recovery after bleaching. Which condition explains this?

    • Answer Options:

    • A. High temperature and low cholesterol

    • B. High cholesterol at moderate temperature

    • C. High unsaturated fatty acids

    • D. Increased protein mobility

  • Correct Answer: Need to reference experimental results to confirm. Answer B

2. Observations Supporting Membrane Asymmetry

  • Question: Which observation BEST supports membrane asymmetry?

    • Answer Options:

    • A. Lipid lateral movement

    • B. Protein rotation

    • C. Carbohydrates only extracellular

    • D. Membrane fluidity

  • Correct Answer: C. Carbohydrates only extracellular - supports the notion that different surfaces of membranes have different compositions.

3. Cell Shrinkage in Hypertonic Solutions

  • Question: A cell shrinks in hypertonic solution because:

    • Answer Options:

    • A. Solute enters

    • B. Water leaves

    • C. ATP pumps water

    • D. Ion channels open

  • Correct Answer: B. Water leaves - In a hypertonic solution, the concentration of solutes outside the cell is greater than inside, leading to water movement out of the cell.

4. Indirect Active Transport Mechanism

  • Question: Which uses indirect active transport?

    • Answer Options:

    • A. O2 diffusion

    • B. Na+ diffusion

    • C. Glucose with Na+

    • D. K+ leak

  • Correct Answer: C. Glucose with Na+ - Glucose enters the cell along with the sodium ion, which is transported based on its gradient.

5. Effects of Stopping the Na+/K+ Pump

  • Question: If Na+/K+ pump stops:

    • Answer Options:

    • A. Na+ decreases inside

    • B. K+ accumulates outside

    • C. Na+ gradient collapses

    • D. Glucose increases

  • Correct Answer: C. Na+ gradient collapses - Without the pump, sodium cannot be extruded from the cell, leading to equal concentrations inside and outside.

6. Consequences of Adenylyl Cyclase Failure

  • Question: If adenylyl cyclase fails:

    • Answer Options:

    • A. ATP rises

    • B. cAMP not made

    • C. GTP not bind

    • D. Ligand fails

  • Correct Answer: B. cAMP not made - Adenylyl cyclase catalyzes the conversion of ATP to cAMP, a secondary messenger crucial for signal transduction.

7. Role of Enzymes

  • Question: Enzymes:

    • Answer Options:

    • A. Make endergonic spontaneous

    • B. Lower activation energy only

    • C. Change equilibrium

    • D. Increase products

  • Correct Answer: B. Lower activation energy only - Enzymes facilitate reactions by lowering the necessary activation energy but do not change the equilibrium or make non-spontaneous reactions spontaneous.

8. Effects of Competitive Inhibition

  • Question: Competitive inhibition causes:

    • Answer Options:

    • A. ↓ Vmax

    • B. ↑ Km

    • C. Permanent stop

    • D. No binding

  • Correct Answer: B. ↑ Km - Competitive inhibitors increase the apparent Km value without affecting Vmax.

9. NAD+ Role in Glycolysis

  • Question: NAD+ in glycolysis:

    • Answer Options:

    • A. Makes ATP

    • B. Donates electrons

    • C. Accepts electrons

    • D. Phosphorylates

  • Correct Answer: C. Accepts electrons - NAD+ is reduced to NADH by accepting electrons during glycolysis.

10. Consequences of Oxygen Absence

  • Question: No oxygen means:

    • Answer Options:

    • A. ATP synthase stops directly

    • B. NADH not made

    • C. No final electron acceptor

    • D. No gradient

  • Correct Answer: C. No final electron acceptor - Oxygen is essential for the electron transport chain as the final electron acceptor, without which aerobic metabolism cannot proceed.

11. Fluidity Restoration in Cold Conditions

  • Question: A membrane becomes rigid in cold conditions. What change restores fluidity?

    • Answer Options:

    • A. More saturated fats

    • B. More cholesterol

    • C. More unsaturated fats

    • D. Less proteins

  • Correct Answer: C. More unsaturated fats - Unsaturated fats introduce kinks in the fatty acid chains, preventing tight packing and enhancing fluidity.

12. Impact of Blocking Na+ Gradient

  • Question: A drug blocks Na+ gradient. What process fails?

    • Answer Options:

    • A. Simple diffusion

    • B. Facilitated diffusion

    • C. Secondary active transport

    • D. Osmosis

  • Correct Answer: C. Secondary active transport - Many secondary active transport mechanisms rely on the sodium gradient to transport other substances across the membrane.

13. Consequence of ATP Binding Mutation on Na+/K+ Pump

  • Question: A mutation prevents ATP binding to Na+/K+ pump. Result?

    • Answer Options:

    • A. Faster pumping

    • B. No ion movement

    • C. Reverse pumping

    • D. Only Na+ moves

  • Correct Answer: B. No ion movement - ATP is required for the function of the Na+/K+ pump; its absence means no active transport can occur.

14. GPCR and G-Protein Activation Failure

  • Question: A GPCR cannot activate G-protein. What fails?

    • Answer Options:

    • A. Ligand binding

    • B. GDP-GTP exchange

    • C. ATP production

    • D. Protein synthesis

  • Correct Answer: B. GDP-GTP exchange - The activation of G-proteins relies on the exchange of GDP for GTP, which is prevented in this scenario.

15. Reasons for Slow Enzyme Activity

  • Question: Enzyme works but reaction still slow. Why?

    • Answer Options:

    • A. ΔG positive

    • B. High activation energy

    • C. Low substrate

    • D. High temp

  • Correct Answer: B. High activation energy - The reaction may still be slow if the activation energy is high, despite the presence of an enzyme.

16. ATP Inhibition of PFK-1

  • Question: High ATP inhibits PFK-1. This is:

    • Answer Options:

    • A. Competitive

    • B. Allosteric

    • C. Irreversible

    • D. Covalent

  • Correct Answer: B. Allosteric - ATP acts as an allosteric inhibitor to PFK-1, regulating glycolysis based on energy needs.

17. Effects of NADH Accumulation without Oxygen

  • Question: NADH accumulates without oxygen. Why is glycolysis affected?

    • Answer Options:

    • A. No ATP

    • B. No NAD+ regeneration

    • C. Glucose gone

    • D. Enzymes denature

  • Correct Answer: B. No NAD+ regeneration - Without oxygen, NADH accumulates and cannot be oxidized back to NAD+, inhibiting glycolysis.

18. Inner Mitochondrial Membrane Folding

  • Question: Inner mitochondrial membrane is folded to:

    • Answer Options:

    • A. Store DNA

    • B. Increase surface area

    • C. Reduce diffusion

    • D. Hold enzymes

  • Correct Answer: B. Increase surface area - The folds, called cristae, increase surface area for ATP production processes.

19. Activation of Uncoupling Proteins

  • Question: Uncoupling proteins active. What happens?

    • Answer Options:

    • A. More ATP

    • B. Heat produced

    • C. No gradient

    • D. No oxygen use

  • Correct Answer: B. Heat produced - Uncoupling proteins dissipate the proton gradient, generating heat instead of ATP.

20. Effects of Mutation Blocking Ras Signaling

  • Question: A mutation blocks Ras signaling. What is affected?

    • Answer Options:

    • A. GPCR signaling

    • B. RTK downstream signaling

    • C. Ion channels

    • D. Glycolysis

  • Correct Answer: B. RTK downstream signaling - Ras is integral to relay signals from receptor tyrosine kinases to various downstream effectors, impacting cell proliferation and differentiation.