Gaokao Exam Gaokao Biology: Cell Biology and Metabolism 3 — Questions and Answers
Question 1: The process by which cells engulf large particles or other cells by membrane folding is called:
- Exocytosis
- Pinocytosis
- Phagocytosis (Correct answer)
- Osmosis
Correct answer: Phagocytosis
Phagocytosis ('cell eating') involves pseudopods engulfing large particles into a phagosome, which then fuses with lysosomes for digestion.
Question 2: Which molecule carries amino acids to the ribosome during translation?
- mRNA
- rRNA
- tRNA (Correct answer)
- snRNA
Correct answer: tRNA
Transfer RNA (tRNA) molecules have anticodons that recognize mRNA codons and carry the corresponding amino acid to the ribosome.
Question 3: Photosystem I (PSI) primarily absorbs light at a peak wavelength of 700 nm and its main function is to:
- Split water molecules and release oxygen
- Reduce NADP⁺ to NADPH (Correct answer)
- Synthesize ATP via chemiosmosis
- Fix carbon dioxide into organic compounds
Correct answer: Reduce NADP⁺ to NADPH
PSI uses light energy to transfer electrons to ferredoxin, which ultimately reduces NADP⁺ to NADPH for use in the Calvin cycle.
Question 4: Which of the following is a characteristic feature distinguishing prokaryotic cells from eukaryotic cells?
- Presence of ribosomes
- Cell membrane made of phospholipids
- Absence of membrane-bound nucleus (Correct answer)
- Ability to carry out cellular respiration
Correct answer: Absence of membrane-bound nucleus
Prokaryotic cells lack a membrane-bound nucleus; their genetic material exists as a nucleoid region in the cytoplasm.
Question 5: The Km (Michaelis constant) of an enzyme is BEST described as:
- The maximum rate of enzyme-catalyzed reaction (Vmax)
- The substrate concentration at which reaction rate is half of Vmax (Correct answer)
- The equilibrium constant of the enzyme-substrate complex
- The number of substrate molecules converted per enzyme per second
Correct answer: The substrate concentration at which reaction rate is half of Vmax
Km represents the substrate concentration at which the reaction velocity is half of Vmax and is an indicator of the enzyme's affinity for its substrate.
Question 6: During interphase, DNA replication occurs in which sub-phase?
- G1 phase
- S phase (Correct answer)
- G2 phase
- M phase
Correct answer: S phase
DNA replication occurs during the S (synthesis) phase of interphase, doubling the cell's genetic material in preparation for cell division.
Question 7: Which product of anaerobic respiration in yeast is commercially important in baking?
- Lactic acid
- Ethanol
- Carbon dioxide (Correct answer)
- Acetyl-CoA
Correct answer: Carbon dioxide
Yeast fermentation produces CO₂ gas that causes bread dough to rise; ethanol is the other product but evaporates during baking.
Gaokao Exam Gaokao Biology: Cell Biology and Metabolism 3
The process by which cells engulf large particles or other cells by membrane folding is called: