Photosynthesis And Cellular Respiration Practice Quiz Questions Ap Biology

Photosynthesis and Cellular Respiration Practice Quiz Questions: AP Biology

This comprehensive quiz will test your knowledge of photosynthesis and cellular respiration, two crucial processes in biology. These questions are designed to mimic the style and difficulty of AP Biology exams, helping you prepare for success. We'll cover key concepts, including the light-dependent and light-independent reactions of photosynthesis, glycolysis, the Krebs cycle, and oxidative phosphorylation. Remember to challenge yourself and review any areas where you feel less confident. Good luck!

Section 1: Photosynthesis

1. What is the overall chemical equation for photosynthesis?

(a) C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP (b) 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (c) C₆H₁₂O₆ + 6O₂ + ATP → 6CO₂ + 6H₂O (d) 6CO₂ + 6O₂ → C₆H₁₂O₆ + 6H₂O

Answer: (b) This equation summarizes the conversion of carbon dioxide and water into glucose and oxygen using light energy.

2. Which of the following is NOT a product of the light-dependent reactions of photosynthesis?

(a) ATP (b) NADPH (c) Glucose (d) Oxygen

Answer: (c) Glucose is synthesized during the light-independent reactions (Calvin cycle). ATP, NADPH, and oxygen are all products of the light-dependent reactions.

3. Where in the chloroplast do the light-dependent reactions take place?

(a) Stroma (b) Thylakoid membrane (c) Grana (d) Both (b) and (c)

Answer: (d) The light-dependent reactions occur within the thylakoid membranes, which are stacked to form grana.

4. Explain the role of chlorophyll in photosynthesis.

Chlorophyll is the primary pigment that absorbs light energy, specifically in the red and blue regions of the electromagnetic spectrum. This absorbed energy is then used to excite electrons, initiating the electron transport chain that leads to ATP and NADPH production. Different types of chlorophyll (a and b) and accessory pigments (like carotenoids) broaden the range of wavelengths absorbed, maximizing the efficiency of photosynthesis.

5. Describe the process of photolysis in the light-dependent reactions.

Photolysis, also known as water splitting, is the process where water molecules are broken down into oxygen, protons (H+), and electrons. This occurs in photosystem II and provides the electrons needed to replace those lost by chlorophyll in the electron transport chain. The oxygen is released as a byproduct, while the protons contribute to the proton gradient used for ATP synthesis.

6. What is the role of RuBisCO in the Calvin cycle?

RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase) is the enzyme that catalyzes the first major step of carbon fixation in the Calvin cycle. It incorporates carbon dioxide from the atmosphere into an existing five-carbon molecule (ribulose-1,5-bisphosphate), forming a six-carbon intermediate that quickly breaks down into two molecules of 3-phosphoglycerate.

7. What are the three main stages of the Calvin cycle? Briefly describe each stage.

The three stages are:

• Carbon Fixation: CO₂ is incorporated into RuBP using RuBisCO, forming a 6-carbon intermediate that immediately splits into two 3-carbon molecules (3-PGA).
• Reduction: ATP and NADPH (from the light-dependent reactions) are used to reduce 3-PGA to glyceraldehyde-3-phosphate (G3P), a three-carbon sugar.
• Regeneration: Some G3P molecules are used to synthesize glucose, while others are used to regenerate RuBP, ensuring the cycle can continue.

8. How does C4 photosynthesis differ from C3 photosynthesis?

C4 photosynthesis is an adaptation that minimizes photorespiration, a process that reduces the efficiency of photosynthesis in hot, dry climates. In C4 plants, CO₂ is initially fixed into a four-carbon compound (oxaloacetate) in mesophyll cells, and then transported to bundle sheath cells where the Calvin cycle occurs. This concentrates CO₂ around RuBisCO, reducing its interaction with oxygen. C3 plants, on the other hand, fix CO₂ directly into RuBP in mesophyll cells.

9. What is CAM photosynthesis, and in what types of plants is it found?

CAM (crassulacean acid metabolism) photosynthesis is another adaptation to arid conditions. CAM plants open their stomata at night to take in CO₂, fixing it into organic acids. During the day, the stomata close to conserve water, and the CO₂ is released from the organic acids and used in the Calvin cycle. This temporal separation of CO₂ uptake and the Calvin cycle minimizes water loss. CAM photosynthesis is found in many succulent plants like cacti and pineapple.

10. Explain the concept of photorespiration and its impact on photosynthetic efficiency.

Photorespiration occurs when RuBisCO binds to oxygen instead of carbon dioxide. This results in the production of a two-carbon compound that is not useful in photosynthesis and requires energy to be processed. Photorespiration reduces the net production of glucose and decreases the overall efficiency of photosynthesis, particularly in hot and dry conditions where oxygen concentration is high and CO₂ concentration is low.

Section 2: Cellular Respiration

1. What is the overall chemical equation for cellular respiration?

(a) 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (b) C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP (c) C₆H₁₂O₆ + 6H₂O + ATP → 6CO₂ + 6O₂ (d) 6CO₂ + 6O₂ → C₆H₁₂O₆ + 6H₂O

Answer: (b) This equation summarizes the breakdown of glucose in the presence of oxygen to produce carbon dioxide, water, and ATP.

2. Where in the cell does glycolysis occur?

(a) Mitochondria (b) Cytoplasm (c) Nucleus (d) Endoplasmic reticulum

Answer: (b) Glycolysis occurs in the cytoplasm of the cell.

3. What are the net products of glycolysis?

(a) 2 ATP, 2 NADH, 2 pyruvate (b) 4 ATP, 2 NADH, 2 pyruvate (c) 2 ATP, 2 FADH₂, 2 pyruvate (d) 4 ATP, 2 FADH₂, 2 pyruvate

Answer: (a) Glycolysis produces a net gain of 2 ATP, 2 NADH, and 2 pyruvate molecules per glucose molecule.

4. What is the role of NADH and FADH₂ in cellular respiration?

NADH and FADH₂ are electron carriers that transport high-energy electrons from glycolysis and the Krebs cycle to the electron transport chain. These electrons are passed down the chain, releasing energy used to pump protons across the mitochondrial membrane, creating a proton gradient that drives ATP synthesis.

5. Where does the Krebs cycle take place?

(a) Cytoplasm (b) Mitochondrial matrix (c) Inner mitochondrial membrane (d) Outer mitochondrial membrane

Answer: (b) The Krebs cycle (also known as the citric acid cycle) takes place in the mitochondrial matrix.

6. What are the products of one turn of the Krebs cycle?

One turn of the Krebs cycle produces: 3 NADH, 1 FADH₂, 1 ATP (or GTP), and 2 CO₂.

7. Describe the process of oxidative phosphorylation.

Oxidative phosphorylation is the final stage of cellular respiration, where the majority of ATP is generated. It involves two main processes:

• Electron Transport Chain: Electrons from NADH and FADH₂ are passed down a series of protein complexes embedded in the inner mitochondrial membrane. This electron transport releases energy used to pump protons from the matrix into the intermembrane space, creating a proton gradient.
• Chemiosmosis: Protons flow back into the matrix through ATP synthase, an enzyme that uses the energy of the proton gradient to synthesize ATP from ADP and inorganic phosphate. This process is called chemiosmosis because it involves the movement of ions across a membrane.

8. What is the role of ATP synthase in oxidative phosphorylation?

ATP synthase is an enzyme that acts as a channel allowing protons to flow back into the mitochondrial matrix. The energy released during this proton flow is coupled to the synthesis of ATP from ADP and inorganic phosphate.

9. How does anaerobic respiration differ from aerobic respiration?

Aerobic respiration requires oxygen as the final electron acceptor in the electron transport chain, while anaerobic respiration does not. Anaerobic respiration yields significantly less ATP than aerobic respiration because the electron transport chain is not fully functional without oxygen. Examples of anaerobic respiration include fermentation (lactic acid or alcoholic fermentation).

10. What are the two main types of fermentation? Briefly describe each.

The two main types of fermentation are:

• Lactic Acid Fermentation: Pyruvate is reduced to lactic acid, regenerating NAD+ so glycolysis can continue. This type of fermentation occurs in muscle cells during strenuous exercise and in some microorganisms.
• Alcoholic Fermentation: Pyruvate is converted to acetaldehyde, which is then reduced to ethanol, regenerating NAD+. This process is used by yeast and some bacteria.

This quiz provides a solid foundation for understanding photosynthesis and cellular respiration. Remember to review the concepts and processes discussed to solidify your understanding and prepare for more advanced topics in AP Biology. Good luck with your studies!