Selected MCQ

Current Question
Release of cytochrome c from mitochondria into the cytosol leads to which cellular process?
  • A. Necrosis
  • B. Apoptosis
  • C. Autophagy
  • D. Mitosis
Correct Answer: B
Explanation:
Cytosolic cytochrome c triggers formation of the apoptosome, leading to caspase activation and programmed cell death (apoptosis).
Related Question 1
Small interfering RNAs (siRNAs) are primarily involved in which cellular process?
  • A. DNA replication
  • B. RNA interference (RNAi) leading to mRNA degradation
  • C. Protein synthesis
  • D. Glycolysis
Correct Answer: B
Explanation:
siRNAs guide the RNA-induced silencing complex (RISC) to complementary mRNA, causing its cleavage and degradation, a form of RNA interference.
Related Question 2
Activation of a Gs protein-coupled receptor typically leads to stimulation of which enzyme to increase intracellular cAMP?
  • A. Protein kinase C
  • B. Adenylyl cyclase
  • C. Phosphodiesterase
  • D. Guanylyl cyclase
Correct Answer: B
Explanation:
Gs α-subunit activates adenylyl cyclase, which converts ATP to cAMP, raising second-messenger levels.
Related Question 3
DNA methylation at CpG islands in gene promoters typically leads to:
  • A. Transcriptional activation
  • B. Transcriptional silencing
  • C. Increased mutation rate
  • D. Immediate DNA repair
Correct Answer: B
Explanation:
Methylation of cytosines in promoters condenses chromatin and represses transcription, silencing the gene.
Related Question 4
Which organelle contains hydrolytic enzymes and is involved in the degradation of cellular components during autophagy?
  • A. Lysosome
  • B. Proteasome
  • C. Golgi apparatus
  • D. Smooth endoplasmic reticulum
Correct Answer: A
Explanation:
Lysosomes contain acid hydrolases that fuse with autophagosomes to degrade cellular organelles and proteins.
Related Question 5
Phospholipase C (PLC) activation results in the generation of which second messenger that releases Ca²⁺ from the endoplasmic reticulum?
  • A. cAMP
  • B. cGMP
  • C. IP₃
  • D. DAG
Correct Answer: C
Explanation:
PLC cleaves PIP₂ into IP₃ and DAG. IP₃ diffuses to the ER, causing Ca²⁺ release, while DAG activates PKC.