Gaokao Biology: Cell Biology and Metabolism Flashcards

Which of the following best describes the function of the smooth endoplasmic reticulum (SER)?

Answer: Lipid synthesis and detoxification

The SER lacks ribosomes and is involved in lipid and steroid synthesis, detoxification of drugs, and calcium storage.

During the Calvin cycle (light-independent reactions), CO₂ is first fixed to produce:

Answer: Two molecules of 3-phosphoglycerate (3-PGA)

RuBisCO catalyzes the carboxylation of RuBP with CO₂ to form an unstable 6-carbon compound that immediately splits into two molecules of 3-PGA.

Which type of transport requires no energy input and moves substances from high to low concentration?

Answer: Facilitated diffusion

Facilitated diffusion uses protein channels or carriers to move substances down their concentration gradient without ATP expenditure.

A competitive inhibitor of an enzyme reduces reaction rate by:

Answer: Occupying the active site and blocking substrate binding

Competitive inhibitors have a structure similar to the substrate and reversibly bind to the active site, competing directly with the substrate.

Which stage of aerobic respiration yields the greatest number of ATP molecules?

Answer: Oxidative phosphorylation (electron transport chain)

Oxidative phosphorylation via the electron transport chain produces approximately 28–32 ATP per glucose, far exceeding the other stages.

In plant cells, the large central vacuole primarily functions to:

Answer: Maintain turgor pressure and store waste products

The central vacuole stores water, ions, and waste products while creating turgor pressure that supports the plant cell and drives cell expansion.

During meiosis, genetic diversity is increased by which two primary mechanisms?

Answer: Crossing over (recombination) and independent assortment

Crossing over during prophase I exchanges segments between homologous chromosomes, while independent assortment randomly distributes homologs to gametes.