Selected MCQ

Current Question
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 1
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 2
Which chromatography technique separates proteins primarily based on size using a gel matrix?
  • A. Ion-exchange chromatography
  • B. Gel filtration (size-exclusion) chromatography
  • C. Affinity chromatography
  • D. Reverse-phase chromatography
Correct Answer: B
Explanation:
Gel filtration chromatography (size-exclusion) separates proteins by size: larger molecules elute first because they enter fewer pores in the matrix, while smaller molecules elute later.
Related Question 3
The insulin receptor has intrinsic kinase activity. Upon insulin binding, which type of residue on the receptor is autophosphorylated?
  • A. Serine
  • B. Threonine
  • C. Tyrosine
  • D. Glycine
Correct Answer: C
Explanation:
The insulin receptor is a tyrosine kinase. Upon ligand binding, it autophosphorylates tyrosine residues on its cytoplasmic domain.
Related Question 4
Gap junction channels between animal cells are formed by which protein?
  • A. Connexin
  • B. Cadherin
  • C. Integrin
  • D. Actin
Correct Answer: A
Explanation:
Connexins assemble into connexons that align between adjacent cells to form gap junction channels for direct cytoplasmic communication.
Related Question 5
Overexpression of the Bcl-2 protein in a cell would most likely result in which effect?
  • A. Increased apoptosis
  • B. Enhanced autophagy
  • C. Resistance to apoptosis
  • D. Increased necrosis
Correct Answer: C
Explanation:
Bcl-2 is an anti-apoptotic protein. Its overexpression makes cells more resistant to apoptotic signals, promoting cell survival.