Selected MCQ

Current Question
Which organelle is primarily responsible for lipid synthesis and detoxification of drugs in liver cells?
  • A. Rough endoplasmic reticulum
  • B. Smooth endoplasmic reticulum
  • C. Golgi apparatus
  • D. Mitochondrion
Correct Answer: B
Explanation:
Smooth ER contains enzymes involved in lipid metabolism and drug detoxification (e.g., cytochrome P450s), especially in hepatocytes.
Related Question 1
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 2
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).
Related Question 3
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 4
In flow cytometry, cells are labeled with fluorescent antibodies and passed in a stream through a laser. This technique primarily measures:
  • A. Cell size and internal complexity
  • B. DNA sequence variants
  • C. Protein structure by X-ray diffraction
  • D. Glycolytic activity
Correct Answer: A
Explanation:
Flow cytometry measures light scattering (size and granularity) and fluorescence from labeled markers, allowing rapid analysis of cell populations (size, complexity, marker expression).
Related Question 5
SDS-PAGE separates proteins primarily based on:
  • A. Charge only
  • B. Size (molecular weight)
  • C. Hydrophobicity
  • D. Isoelectric point
Correct Answer: B
Explanation:
SDS denatures proteins and coats them with a negative charge that is proportional to their length. In SDS-PAGE, proteins are separated by size; smaller proteins migrate faster.