Problem 3 - Biology of Humans: Concepts, Applications, and Issues

Question

Choose the incorrect statement: a. Cellular respiration requires oxygen. b. Glycolysis occurs in both cellular respiration and fermentation. c. Cellular respiration yields more ATP per molecule of glucose than does fermentation. d. Fermentation occurs in mitochondria.

Step-by-Step Solution

Answer

d. Fermentation occurs in mitochondria is incorrect.

Step 1: Identify and Understand Each Statement

Read each statement carefully to understand its meaning: - (a) Cellular respiration requires oxygen. - (b) Glycolysis occurs in both cellular respiration and fermentation. - (c) Cellular respiration yields more ATP per molecule of glucose than does fermentation. - (d) Fermentation occurs in mitochondria.

Step 2: Verify Statement (a)

Statement (a) is correct because cellular respiration is an aerobic process that requires oxygen.

Step 3: Verify Statement (b)

Statement (b) is correct. Glycolysis is the first step in both cellular respiration and fermentation.

Step 4: Verify Statement (c)

Statement (c) is correct. Cellular respiration produces significantly more ATP per glucose molecule compared to fermentation.

Step 5: Verify Statement (d)

Statement (d) is incorrect. Fermentation occurs in the cytoplasm, not in the mitochondria.

Step 6: Conclusion

After verifying all statements, it is clear that the incorrect statement is (d).

Key Concepts

aerobic process

An aerobic process is a type of cellular respiration that requires oxygen to produce energy. Cellular respiration, specifically, depends on oxygen to convert glucose into ATP (adenosine triphosphate), which cells use for energy. This process takes place primarily within the mitochondria, the powerhouse of the cell. One of the main advantages of aerobic respiration is its efficiency in producing ATP. For each molecule of glucose, aerobic respiration can generate up to 36-38 ATP molecules. This sufficiency makes it the preferred method of energy production in most eukaryotic cells. Also, consider that aerobic processes contribute to the breakdown of by-products like carbon dioxide and water, making it a clean and efficient energy cycle. Oxygen, hence, acts as the final electron acceptor in the electron transport chain, a series of reactions in the mitochondria.

anaerobic process

An anaerobic process is another way cells produce energy, but it does not require oxygen. Fermentation is a common anaerobic process. While less efficient than aerobic respiration, it allows organisms to generate ATP when oxygen is scarce. In the absence of oxygen, cells rely on fermentation to convert glucose into energy. The process primarily occurs in the cytoplasm of the cell, bypassing the mitochondria. There are two main types of fermentation: lactic acid fermentation and alcoholic fermentation. Lactic acid fermentation occurs in muscle cells and certain bacteria, producing lactic acid as a byproduct. Alcoholic fermentation, on the other hand, takes place in yeast and some types of bacteria, producing ethanol and carbon dioxide. Despite only generating 2 ATP molecules per glucose molecule, fermentation is vital for short bursts of energy, especially in anaerobic environments.

ATP production

ATP (adenosine triphosphate) is the energy currency of the cell. Both aerobic and anaerobic processes aim to produce ATP from glucose to fuel cellular activities. In cellular respiration, the process unfolds in several stages: glycolysis, the Krebs cycle, and the electron transport chain. Glycolysis breaks down glucose molecules into pyruvate, generating 2 ATP molecules. The Krebs cycle further processes pyruvate in the mitochondria to produce more electron carriers for the electron transport chain. The final step, the electron transport chain, produces the majority of ATP, up to 34 molecules. Conversely, in fermentation, glycolysis remains the primary method for ATP production, as the pyruvate is converted into either lactic acid or ethanol. Despite its lower yield, fermentation is essential for survival in oxygen-poor conditions. Understanding ATP production is critical for grasping why different organisms rely on different metabolic pathways given their environments.