Selected MCQ

Current Question
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 1
Activation of a Gq-coupled receptor leads to which immediate change in second messenger levels?
  • A. Activation of adenylate cyclase and an increase in cAMP
  • B. Activation of phospholipase C (PLC) and increase in IP3 and DAG
  • C. Opening of potassium channels and membrane hyperpolarization
  • D. Activation of tyrosine kinase receptors and phosphorylation of STAT proteins
Correct Answer: B
Explanation:
Gq proteins activate phospholipase C, which cleaves PIP2 into IP3 and DAG. IP3 increases intracellular Ca2+, and DAG activates protein kinase C.
Related Question 2
In Western blotting, proteins are typically detected using:
  • A. DNA probes
  • B. RNA probes
  • C. Enzyme-linked antibodies
  • D. Radioactive amino acids
Correct Answer: C
Explanation:
Western blot uses antibodies (often enzyme-linked) that bind specific proteins on the membrane, allowing visualization via a colorimetric or chemiluminescent reaction.
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
Binding of extracellular matrix protein fibronectin to a cell’s integrin receptor most directly triggers which intracellular signaling pathway?
  • A. cAMP/PKA pathway
  • B. MAP kinase (ERK) pathway
  • C. JAK/STAT pathway
  • D. Hedgehog signaling pathway
Correct Answer: B
Explanation:
Integrin activation often activates focal adhesion kinase and the MAPK/ERK cascade, promoting cell survival and proliferation.
Related Question 5
In tissue engineering, a scaffold material must typically be:
  • A. Non-biodegradable only
  • B. Biocompatible and biodegradable
  • C. Made of metal only
  • D. Radioactive
Correct Answer: B
Explanation:
Tissue scaffolds are usually biocompatible (non-toxic, no immune response) and biodegradable so that they eventually degrade as new tissue forms in the scaffold’s place.