AP Biology: Cellular Respiration
15 practice questions · 15 flashcards · made from study notes
Terms in this set (15)
- What is the primary purpose of cellular respiration?
- To release energy stored in glucose and capture it as ATP.
- What is the overall chemical equation for cellular respiration?
- C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy
- The first stage of cellular respiration, ___, occurs in the cytoplasm and does not require oxygen.
- Glycolysis
- How many net ATP molecules are produced during glycolysis per glucose molecule?
- 2 ATP
- Define pyruvate oxidation.
- The process where each pyruvate is converted into acetyl-CoA, releasing one CO2 and producing one NADH.
- Where does the Krebs cycle (citric acid cycle) take place?
- In the mitochondrial matrix
- For each turn of the Krebs cycle, how many NADH, FADH2, and ATP (or GTP) molecules are produced?
- 3 NADH, 1 FADH2, 1 ATP (or GTP)
- Oxidative phosphorylation occurs on the ___ mitochondrial membrane.
- inner
- What is the role of oxygen in oxidative phosphorylation?
- It is the final electron acceptor, combining with electrons and protons to form water.
- Define chemiosmosis.
- The coupling of the proton gradient to ATP synthesis by ATP synthase.
- Approximately how many ATP molecules are produced by oxidative phosphorylation per glucose molecule?
- 26 to 28 ATP
- What is the primary function of fermentation?
- To regenerate NAD+ so glycolysis can continue in the absence of oxygen.
- In animal muscle cells, pyruvate is converted to ___ during fermentation.
- lactate
- How do cyanide and carbon monoxide affect cellular respiration?
- They block complex IV of the electron transport chain, preventing electrons from reaching oxygen and collapsing ATP synthesis.
- What is the effect of uncoupling proteins like thermogenin?
- They allow protons to leak across the inner mitochondrial membrane without passing through ATP synthase, releasing energy as heat instead of ATP.
Practice questions (15)
1.In the process of cellular respiration, which stage takes place in the cytoplasm of the cell?
- AGlycolysis
- BThe Krebs cycle
- COxidative phosphorylation
- DPyruvate oxidation
Show answer
Answer: Glycolysis
This question checks the student's understanding of the specific location of the first stage of cellular respiration. Glycolysis is unique among the main stages for occurring in the cytoplasm, while the others are located within the mitochondria.
2.True or False: The Krebs cycle, also known as the citric acid cycle, occurs in the intermembrane space of the mitochondrion.
- ATrue
- BFalse
Show answer
Answer: False
This question tests the student's precise knowledge of the sub-cellular locations for the stages of respiration. The Krebs cycle happens in the mitochondrial matrix, not the intermembrane space, which is where protons are pumped during oxidative phosphorylation.
3.What are the three main products of the Krebs cycle for each molecule of acetyl-CoA that enters it?
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Answer: For each acetyl-CoA, the Krebs cycle produces 3 NADH, 1 FADH2, and 1 ATP (or GTP). It also releases 2 CO2.
This question requires the student to recall the specific outputs of the Krebs cycle, which are crucial for understanding how this stage contributes to the overall energy yield of cellular respiration, primarily by producing electron carriers for the next stage.
4.The process of splitting a 6-carbon glucose molecule into two 3-carbon pyruvate molecules is known as glycolysis. Where does this process occur, and does it require oxygen?
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Answer: Glycolysis occurs in the cytoplasm and it does not require oxygen.
This question assesses the student's ability to identify the location and oxygen requirement of glycolysis, fundamental characteristics that distinguish it from the aerobic stages of respiration.
5.During which stage of cellular respiration are the electron carriers NADH and FADH2 used to generate a proton gradient?
- AGlycolysis
- BOxidative phosphorylation
- CThe Krebs cycle
- DPyruvate oxidation
Show answer
Answer: Oxidative phosphorylation
This question links the electron carriers produced in earlier stages to their function in the final stage. Understanding that NADH and FADH2 'drop off' their electrons to power the electron transport chain is key to seeing how the stages are connected.
6.Pyruvate oxidation is a short but crucial step linking glycolysis to the Krebs cycle. What is the location of this process inside the cell?
Show answer
Answer: Pyruvate oxidation occurs in the mitochondrial matrix.
This question focuses on the specific location of the intermediate step, pyruvate oxidation. Knowing that pyruvate must be transported into the mitochondrial matrix to be converted into acetyl-CoA is important for understanding the sequence and compartmentalization of respiration.
7.True or False: Oxidative phosphorylation, the stage that produces the most ATP, takes place on the inner mitochondrial membrane.
- ATrue
- BFalse
Show answer
Answer: True
This question confirms the student's knowledge of the location of the most productive stage of ATP synthesis. The folding of the inner mitochondrial membrane into cristae increases the surface area for this process, highlighting the importance of this specific location.
8.Which of the following correctly pairs a stage of cellular respiration with its location?
- AKrebs cycle - Cytoplasm
- BGlycolysis - Mitochondrial matrix
- COxidative phosphorylation - Inner mitochondrial membrane
- DPyruvate oxidation - Intermembrane space
Show answer
Answer: Oxidative phosphorylation - Inner mitochondrial membrane
This question challenges students to evaluate multiple pairs of processes and locations, requiring a comprehensive understanding of the geography of cellular respiration. It helps consolidate their knowledge of where each key event happens.
9.Imagine a cell is treated with a poison that specifically blocks the transport of pyruvate into the mitochondrial matrix. Which stage(s) of aerobic respiration would be directly halted?
Show answer
Answer: Pyruvate oxidation and the Krebs cycle would be directly halted because their substrate, pyruvate, cannot reach the mitochondrial matrix where they occur. Oxidative phosphorylation would also stop soon after as the supply of NADH and FADH2 from these stages is cut off.
This question requires students to apply their knowledge of the sequence and location of respiratory stages to a hypothetical scenario. It challenges them to reason about the downstream consequences of a specific disruption, deepening their understanding of the pathway's interconnectedness.
10.True or false: Both aerobic respiration and anaerobic fermentation begin with the process of glycolysis, which occurs in the cytoplasm and splits glucose into pyruvate.
- ATrue
- BFalse
Show answer
Answer: True
This question highlights a critical similarity between the two pathways. It confirms that students recognize glycolysis as the universal first step for breaking down glucose, regardless of whether oxygen is present or not.
11.What is the primary reason that fermentation is necessary for cells in the absence of oxygen, even though it doesn't produce any additional ATP beyond glycolysis?
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Answer: Fermentation is necessary to regenerate NAD+ from the NADH produced during glycolysis. Without oxygen, the electron transport chain cannot operate to recycle NADH back to NAD+. If NAD+ runs out, glycolysis would halt, and the cell would be unable to produce any ATP at all.
This question challenges students to think beyond just ATP yield and understand the critical role of electron carriers. It requires them to connect the halt of the electron transport chain to the need for an alternative pathway (fermentation) to sustain even the minimal ATP production from glycolysis.
12.If a yeast cell is grown in a sealed container with glucose, what final products would you expect to find after it has used up all the glucose?
- ALactate and ATP
- BCO2, water, and ATP
- CPyruvate, NADH, and ATP
- DEthanol, CO2, and ATP
Show answer
Answer: Ethanol, CO2, and ATP
This question asks students to apply their knowledge of anaerobic pathways to a specific organism (yeast). It tests their ability to recall the specific end products of alcoholic fermentation, distinguishing it from lactic acid fermentation and aerobic respiration.
13.Consider the overall chemical equation for aerobic respiration: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O. How does this equation differ from the overall process of anaerobic fermentation in terms of reactants and products?
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Answer: Anaerobic fermentation does not use oxygen (O2) as a reactant. Its products are not CO2 and water; instead, they are either lactate (in lactic acid fermentation) or ethanol and CO2 (in alcoholic fermentation). The breakdown of glucose is incomplete.
This question requires a direct comparison at the level of chemical inputs and outputs. It pushes students to analyze the summary equation for aerobic respiration and contrast it with the outcomes of fermentation, reinforcing the concepts of oxygen requirement and the final products of each pathway.
14.True or false: In aerobic respiration, oxygen is the final electron acceptor in the electron transport chain, but in fermentation, pyruvate (or a derivative of it) serves a similar role by accepting electrons from NADH.
- ATrue
- BFalse
Show answer
Answer: True
This question challenges students to think functionally about the role of different molecules in both processes. Recognizing that pyruvate (or its derivatives like acetaldehyde) acts as an electron acceptor in fermentation to regenerate NAD+ demonstrates a deeper, comparative understanding of the redox reactions that are central to both aerobic and anaerobic metabolism.
15.The enzyme phosphofructokinase is a key regulator of glycolysis, the first stage of cellular respiration. If a cell has a very high concentration of ATP, what effect would this have on the activity of phosphofructokinase?
- AIt would increase its activity, speeding up glycolysis.
- BIt would have no effect on its activity.
- CIt would inhibit its activity, slowing down glycolysis.
- DIt would change its function to produce ATP instead of consuming it.
Show answer
Answer: It would inhibit its activity, slowing down glycolysis.
This question challenges the student to apply the concept of feedback inhibition, a key principle in metabolic regulation. Understanding that high levels of a pathway's final product (ATP) can inhibit an early enzyme (phosphofructokinase) demonstrates a deeper comprehension of how cells efficiently manage their energy resources. It moves beyond simple memorization of the steps to analyzing the control mechanisms.
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