CLEP - Biology Cellular Respiration and Photosynthesis Questions and Answers — Questions and Answers
Question 1: Which of the following correctly describes a key difference between the Krebs cycle and the Calvin cycle?
- The Krebs cycle is a catabolic pathway that produces ATP, while the Calvin cycle is an anabolic pathway that consumes ATP. (Correct answer)
- The Krebs cycle occurs in the chloroplast stroma, while the Calvin cycle occurs in the mitochondrial matrix.
- The Krebs cycle is the final stage of photosynthesis, while the Calvin cycle is the first stage of cellular respiration.
- The Krebs cycle utilizes carbon dioxide to produce glucose, while the Calvin cycle breaks down glucose to release carbon dioxide.
Correct answer: The Krebs cycle is a catabolic pathway that produces ATP, while the Calvin cycle is an anabolic pathway that consumes ATP.
The Krebs cycle (part of cellular respiration) is a catabolic process because it breaks down molecules (acetyl-CoA) to release energy, producing ATP. In contrast, the Calvin cycle (part of photosynthesis) is an anabolic process because it uses energy (ATP and NADPH) to build larger molecules (sugars) from smaller ones (CO2).
Question 2: A scientist is studying a cell that has been treated with a chemical that makes the inner mitochondrial membrane permeable to protons (H+). Which of the following cellular processes would be most directly and severely affected?
- Glycolysis
- The Krebs Cycle
- Oxidative Phosphorylation (Correct answer)
- The Calvin Cycle
Correct answer: Oxidative Phosphorylation
Oxidative phosphorylation relies on a proton gradient across the inner mitochondrial membrane to power ATP synthase. If this membrane becomes permeable to protons, the gradient will dissipate, and ATP synthase will be unable to produce large amounts of ATP. Glycolysis occurs in the cytoplasm and does not require a proton gradient. The Krebs cycle occurs in the mitochondrial matrix and while it provides electrons for the ETC, it is not directly inhibited by a leaky membrane. The Calvin Cycle is part of photosynthesis and occurs in chloroplasts.
Question 3: In the overall process of photosynthesis, the oxygen (O2) released comes from which molecule?
- Carbon dioxide (CO2)
- Glucose (C6H12O6)
- Water (H2O) (Correct answer)
- ATP
Correct answer: Water (H2O)
During the light-dependent reactions of photosynthesis, water molecules are split (a process called photolysis) to release electrons, protons (H+), and oxygen gas (O2). The oxygen is then released as a byproduct.
Question 4: Which of the following statements accurately compares the electron transport chains (ETCs) in cellular respiration and photosynthesis?
- Both ETCs are located in the mitochondrial matrix.
- In both processes, the final electron acceptor is oxygen.
- Both processes use the ETC to pump protons and generate a chemiosmotic gradient for ATP synthesis. (Correct answer)
- Photosynthesis uses the ETC to break down glucose, while cellular respiration uses it to build glucose.
Correct answer: Both processes use the ETC to pump protons and generate a chemiosmotic gradient for ATP synthesis.
A primary function of the electron transport chain in both aerobic respiration (in mitochondria) and the light-dependent reactions of photosynthesis (in chloroplasts) is to use the energy from electron flow to pump protons across a membrane. This creates a proton gradient (chemiosmotic gradient) that drives the synthesis of ATP by ATP synthase.
Question 5: The primary function of the light-independent reactions (Calvin cycle) in photosynthesis is to:
- Capture light energy and convert it to chemical energy.
- Use ATP and NADPH to synthesize carbohydrates from carbon dioxide. (Correct answer)
- Split water molecules to release oxygen.
- Break down glucose to produce ATP.
Correct answer: Use ATP and NADPH to synthesize carbohydrates from carbon dioxide.
The Calvin cycle, also known as the light-independent reactions, uses the chemical energy (ATP and NADPH) produced during the light-dependent reactions to fix inorganic carbon (from CO2) into organic sugar molecules.
Question 6: Which process occurs in the cytoplasm of a eukaryotic cell and functions in both aerobic and anaerobic respiration?
- Krebs Cycle
- Electron Transport Chain
- Glycolysis
- Fermentation (Correct answer)
Correct answer: Fermentation
Glycolysis is the initial metabolic pathway that breaks down glucose into pyruvate. It occurs in the cytoplasm and does not require oxygen, making it a universal first step for both aerobic respiration and anaerobic pathways like fermentation.
CLEP - Biology Cellular Respiration and Photosynthesis Questions and Answers
Which of the following correctly describes a key difference between the Krebs cycle and the Calvin cycle?