Gaokao Exam Gaokao Biology: Cell Biology and Metabolism 5 — Questions and Answers
Question 1: The P/O ratio in cellular respiration refers to:
- The ratio of pyruvate produced to oxygen consumed in glycolysis
- The number of ATP molecules synthesized per oxygen atom reduced (Correct answer)
- The ratio of NADH to FADH₂ produced in the Krebs cycle
- The partial pressure of oxygen in the mitochondrial matrix
Correct answer: The number of ATP molecules synthesized per oxygen atom reduced
The P/O ratio quantifies oxidative phosphorylation efficiency — approximately 2.5 ATP are produced per NADH and 1.5 ATP per FADH₂ oxidized.
Question 2: Which of the following best describes a secondary active transport mechanism?
- Direct use of ATP to pump a molecule against its gradient
- Co-transport using the electrochemical gradient established by primary active transport (Correct answer)
- Movement of a molecule down its concentration gradient via a channel protein
- Bulk transport of large molecules via membrane vesicles
Correct answer: Co-transport using the electrochemical gradient established by primary active transport
Secondary active transport uses the electrochemical gradient (often Na⁺ gradient created by the Na⁺/K⁺ pump) to co-transport another molecule against its gradient without direct ATP use.
Question 3: In the light-harvesting complex of chloroplasts, energy from absorbed photons is transferred to the reaction center by:
- ATP hydrolysis
- Resonance energy transfer between pigment molecules (Correct answer)
- Electron transport chain proteins
- Proton gradient across thylakoid membrane
Correct answer: Resonance energy transfer between pigment molecules
Excited electrons in antenna pigment molecules transfer energy via resonance (Förster energy transfer) through successive pigment molecules to the reaction center chlorophyll.
Question 4: Lysosomes are formed by budding from which organelle?
- Mitochondria
- Endoplasmic reticulum
- Golgi apparatus (Correct answer)
- Nucleus
Correct answer: Golgi apparatus
Lysosomes are formed when vesicles containing hydrolytic enzymes bud from the trans face of the Golgi apparatus.
Question 5: The Q10 coefficient in biology measures:
- The ratio of enzyme activity at pH 10 versus pH 7
- The ratio of reaction rate at a temperature T+10°C versus temperature T (Correct answer)
- The activation energy required for a reaction at 10°C
- The number of substrates processed per enzyme at 37°C
Correct answer: The ratio of reaction rate at a temperature T+10°C versus temperature T
Q10 is the factor by which a biological process rate changes per 10°C temperature increase; most metabolic reactions have a Q10 of 2–3.
Question 6: Which stage of mitosis is characterized by chromosomes aligned along the cell's equatorial plate?
- Prophase
- Metaphase (Correct answer)
- Anaphase
- Telophase
Correct answer: Metaphase
During metaphase, condensed chromosomes are aligned along the metaphase plate by balanced tension from spindle fibers attached to kinetochores on each sister chromatid.
Question 7: Acetyl-CoA enters the Krebs cycle by combining with which 4-carbon molecule?
- Pyruvate
- Succinate
- Oxaloacetate (Correct answer)
- Fumarate
Correct answer: Oxaloacetate
Acetyl-CoA (2C) condenses with oxaloacetate (4C) to form citrate (6C), the first compound of the Krebs cycle.
Gaokao Exam Gaokao Biology: Cell Biology and Metabolism 5
The P/O ratio in cellular respiration refers to: