Selected MCQ

Current Question
Which feature of mitochondrial structure most directly facilitates ATP synthesis via oxidative phosphorylation?
  • A. Large pores in the outer membrane allowing free movement of ions
  • B. Extensive folding of the inner membrane into cristae
  • C. Circular DNA encoding the majority of electron transport proteins
  • D. Abundant ribosomes within the mitochondrial matrix
Correct Answer: B
Explanation:
The inner mitochondrial membrane is highly folded into cristae, increasing surface area for the electron transport chain complexes and ATP synthase to produce ATP.
Related Question 1
A mutation in nuclear lamin would most directly impair which cellular structure?
  • A. Alignment of chromosomes during metaphase
  • B. Anchoring of the nucleus to the cytoskeleton
  • C. Organization and structural integrity of the nuclear envelope
  • D. Export of mRNA through nuclear pores
Correct Answer: C
Explanation:
Lamins are intermediate filament proteins that form a network lining the inner nuclear membrane. Mutations disrupt the nuclear envelope’s stability and organization.
Related Question 2
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 3
A mutation prevents dynein from binding microtubules in eukaryotic cells. Which of the following processes would be most directly impaired?
  • A. Skeletal muscle contraction
  • B. Movement of vesicles from the Golgi apparatus to the endoplasmic reticulum
  • C. Movement of chromosomes toward the spindle poles during mitosis
  • D. Sliding of microtubule doublets in eukaryotic cilia and flagella
Correct Answer: D
Explanation:
Dynein motor proteins drive the sliding of microtubule doublets in cilia and flagella. Without functional dynein, ciliary and flagellar motion would be impaired. (Other processes involve myosin or different motor proteins.)
Related Question 4
Which structural feature is shared by B-DNA, A-DNA, and Z-DNA?
  • A. Right-handed double helix
  • B. 10 bases per turn
  • C. Uniform major groove
  • D. Two strands paired by base complementarity
Correct Answer: D
Explanation:
All DNA forms (B, A, Z) are double-stranded helices with complementary base pairing. However, B and A are right-handed (10 and ~11 bp/turn), and Z is left-handed.
Related Question 5
In a DNA molecule, 5′ to 3′ synthesis means:
  • A. New nucleotides are added at the 5′ end of the new strand
  • B. New nucleotides are added at the 3′ end of the new strand
  • C. DNA is always read 5′ to 3′ on the template
  • D. The sugar backbone runs from 5′ to 3′
Correct Answer: B
Explanation:
DNA polymerases add nucleotides to the 3′-OH end of a growing strand, so synthesis proceeds in the 5′→3′ direction (extending at the 3′ end).