Gaokao Biology: Cell Biology and Metabolism Flashcards

The P/O ratio in cellular respiration refers to:

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.

Which of the following best describes a secondary active transport mechanism?

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.

In the light-harvesting complex of chloroplasts, energy from absorbed photons is transferred to the reaction center by:

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.

Lysosomes are formed by budding from which organelle?

Answer: Golgi apparatus

Lysosomes are formed when vesicles containing hydrolytic enzymes bud from the trans face of the Golgi apparatus.

The Q10 coefficient in biology measures:

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.

Which stage of mitosis is characterized by chromosomes aligned along the cell's equatorial plate?

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.

Acetyl-CoA enters the Krebs cycle by combining with which 4-carbon molecule?

Answer: Oxaloacetate

Acetyl-CoA (2C) condenses with oxaloacetate (4C) to form citrate (6C), the first compound of the Krebs cycle.