Gaokao Exam Gaokao Biology: Cell Biology and Metabolism 1 — Questions and Answers
Question 1: Which organelle is responsible for the production of ATP through aerobic cellular respiration in eukaryotic cells?
- Chloroplast
- Ribosome
- Mitochondria (Correct answer)
- Golgi apparatus
Correct answer: Mitochondria
Mitochondria are the site of aerobic respiration, producing the majority of ATP via oxidative phosphorylation in the inner membrane.
Question 2: During the light-dependent reactions of photosynthesis, which molecule acts as the primary electron donor?
- NADPH
- Water (H₂O) (Correct answer)
- Carbon dioxide (CO₂)
- Glucose
Correct answer: Water (H₂O)
Water is split by photolysis in Photosystem II, donating electrons to replace those lost by chlorophyll and releasing O₂ as a byproduct.
Question 3: The fluid mosaic model of the cell membrane describes the membrane as composed primarily of:
- Glycogen and cholesterol
- A phospholipid bilayer with embedded proteins (Correct answer)
- Cellulose fibers with channel proteins
- A single layer of lipids and carbohydrates
Correct answer: A phospholipid bilayer with embedded proteins
The fluid mosaic model describes the membrane as a dynamic phospholipid bilayer in which proteins float and move laterally.
Question 4: An enzyme-catalyzed reaction proceeds 1000 times faster than the uncatalyzed reaction. The enzyme achieves this by:
- Increasing the overall free energy change (ΔG)
- Providing an alternative pathway with lower activation energy (Correct answer)
- Increasing substrate concentration
- Changing the equilibrium constant of the reaction
Correct answer: Providing an alternative pathway with lower activation energy
Enzymes lower the activation energy by stabilizing the transition state, allowing more substrate molecules to reach the transition state at a given temperature.
Question 5: In which phase of mitosis do sister chromatids separate and move to opposite poles of the cell?
- Prophase
- Metaphase
- Anaphase (Correct answer)
- Telophase
Correct answer: Anaphase
During anaphase, cohesin proteins are cleaved, allowing sister chromatids to separate and be pulled to opposite poles by spindle fibers.
Question 6: Which of the following statements about cellular respiration is CORRECT?
- Glycolysis requires oxygen and occurs in the mitochondrial matrix
- The Krebs cycle produces a net of 34 ATP per glucose molecule
- Glycolysis converts one glucose molecule into two pyruvate molecules with a net gain of 2 ATP (Correct answer)
- Oxidative phosphorylation occurs in the cytoplasm
Correct answer: Glycolysis converts one glucose molecule into two pyruvate molecules with a net gain of 2 ATP
Glycolysis in the cytoplasm converts glucose (6C) into two pyruvate molecules (3C each), with a net gain of 2 ATP and 2 NADH.
Question 7: The sodium-potassium pump (Na⁺/K⁺-ATPase) maintains the resting membrane potential by:
- Moving 2 Na⁺ out and 3 K⁺ into the cell per cycle
- Moving 3 Na⁺ out and 2 K⁺ into the cell per cycle using ATP (Correct answer)
- Allowing passive diffusion of both ions down their gradients
- Using NADPH energy to pump equal numbers of both ions
Correct answer: Moving 3 Na⁺ out and 2 K⁺ into the cell per cycle using ATP
The pump actively transports 3 Na⁺ out and 2 K⁺ in per ATP hydrolyzed, creating the electrochemical gradient essential for nerve and muscle function.
Gaokao Exam Gaokao Biology: Cell Biology and Metabolism 1
Which organelle is responsible for the production of ATP through aerobic cellular respiration in eukaryotic cells?