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MCQ Practice

General Science (Everyday Science) MCQs

Which level of protein structure is most directly stabilized by hydrogen bonds between backbone groups?

  • A. Primary
  • B. Secondary
  • C. Tertiary only
  • D. Quaternary only
Explanation:
(\alpha)-helices and (\beta)-sheets arise from backbone hydrogen bonding patterns.

Enzyme specificity is primarily determined by the:

  • A. Number of peptide bonds
  • B. Shape and chemical environment of the active site
  • C. Presence of DNA in the cytoplasm
  • D. Color of the substrate
Explanation:
Complementary structure and chemistry of the active site govern substrate binding and catalysis.

In oxidative phosphorylation, oxygen serves as the terminal:

  • A. Electron donor
  • B. ATP inhibitor
  • C. Electron acceptor
  • D. Proton source only
Explanation:
(O_2) accepts electrons at the end of the mitochondrial electron transport chain.

Which process occurs in the thylakoid membranes of chloroplasts?

  • A. Calvin cycle carbon fixation
  • B. Light-dependent reactions
  • C. Glycolysis
  • D. DNA replication only
Explanation:
Photosystems and electron transport chains of photosynthesis are membrane embedded.

The primary role of ribosomes is to:

  • A. Replicate DNA
  • B. Synthesize proteins
  • C. Digest lipids
  • D. Store calcium
Explanation:
Ribosomes translate mRNA into polypeptides.

Which molecule is the immediate donor of phosphate in many cellular energy-transfer reactions?

  • A. NADH
  • B. ATP
  • C. DNA
  • D. Glycogen
Explanation:
ATP hydrolysis commonly drives endergonic reactions via phosphate transfer.

Independent assortment occurs because homologous chromosome pairs:

  • A. Replicate at different times
  • B. Align randomly at metaphase I
  • C. Separate in mitosis only
  • D. Undergo mutation during cytokinesis
Explanation:
Random orientation of homologs generates different combinations in gametes.

Crossing over during meiosis contributes directly to:

  • A. DNA replication arrest
  • B. Genetic recombination
  • C. Chromosome number doubling
  • D. Cytokinesis prevention
Explanation:
Exchange between homologous chromatids creates new allele combinations.

Which mutation is least likely to alter protein sequence?

  • A. Missense mutation
  • B. Nonsense mutation
  • C. Silent mutation
  • D. Frameshift mutation
Explanation:
Due to genetic code degeneracy, a silent change can preserve the same amino acid.

In eukaryotes, transcription occurs primarily in the:

  • A. Ribosome
  • B. Cytosol
  • C. Nucleus
  • D. Mitochondrial matrix only
Explanation:
Nuclear DNA is transcribed in the nucleus before most mRNA is exported.