Selected MCQ

Current Question
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 1
The smooth endoplasmic reticulum (SER) is primarily involved in which of the following cellular functions?
  • A. Synthesis of secretory and membrane proteins
  • B. Detoxification of xenobiotics and synthesis of lipids
  • C. ATP production via oxidative phosphorylation
  • D. Packaging and modification of proteins in vesicles
Correct Answer: B
Explanation:
The smooth ER specializes in lipid and steroid synthesis, as well as the detoxification of drugs and other harmful compounds. (Protein synthesis occurs on the rough ER; packaging occurs in the Golgi.)
Related Question 2
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 3
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 4
Which organelle is primarily involved in the detoxification of hydrogen peroxide (H₂O₂) in eukaryotic cells?
  • A. Lysosome
  • B. Mitochondrion
  • C. Peroxisome
  • D. Golgi apparatus
Correct Answer: C
Explanation:
Peroxisomes contain the enzyme catalase, which converts H₂O₂ to water and oxygen. They specialize in detoxifying reactive oxygen species.
Related Question 5
The 5′ cap added to eukaryotic mRNAs is:
  • A. A string of adenine residues at the 5′ end
  • B. A modified guanosine (7-methylguanosine) linked 5′→5′
  • C. A poly-uridine sequence at the 3′ end
  • D. A phosphate group at the 5′ end
Correct Answer: B
Explanation:
The 5′ cap is a 7-methylguanosine joined via a 5′-to-5′ triphosphate linkage to the first nucleotide of the mRNA, protecting it from degradation and aiding translation.