Exercising and working muscles, as athletes do, causes:

• A. a suppression of homeostatic mechanisms regulating body temperature
• B. an increase in cellular respiration and ATP production
• C. a decrease in oxygen demand by muscle cells
• D. a reduction in metabolic waste products such as lactic acid

Answer: (B)

Verified step by step guidance

1. Understand the context: When muscles are exercised, they require more energy to perform their functions. This energy is provided by cellular respiration, which involves the breakdown of glucose to produce ATP (adenosine triphosphate). ATP is the primary energy currency of the cell.
2. Step 1: Analyze the first option: 'a suppression of homeostatic mechanisms regulating body temperature.' This is incorrect because homeostatic mechanisms, such as sweating and increased blood flow to the skin, are activated during exercise to regulate body temperature, not suppressed.
3. Step 2: Analyze the second option: 'an increase in cellular respiration and ATP production.' This is correct because working muscles require more ATP, which is produced through increased cellular respiration. Cellular respiration involves glycolysis, the citric acid cycle, and oxidative phosphorylation, which collectively generate ATP.
4. Step 3: Analyze the third option: 'a decrease in oxygen demand by muscle cells.' This is incorrect because exercising muscles have a higher demand for oxygen to support aerobic respiration. Oxygen is required for the efficient production of ATP in the mitochondria.
5. Step 4: Analyze the fourth option: 'a reduction in metabolic waste products such as lactic acid.' This is incorrect because during intense exercise, when oxygen supply is insufficient, muscles switch to anaerobic respiration, leading to the production of lactic acid as a byproduct.