The correct option is A is false but R is true
Explanation
The question addresses the pathways of anaerobic respiration (breakdown of glucose in the absence of oxygen) in different organisms. While the initial step of breaking down glucose into pyruvate (glycolysis) is common to all organisms, the subsequent fate of pyruvate depends on the presence of oxygen and the type of cell involved.
Analysis of Assertion (A):
Incorrect. During heavy physical exercise, the demand for energy is high, but the supply of oxygen to muscle cells may be insufficient. In this anaerobic condition, human muscle cells break down pyruvate to produce Lactic Acid and energy. They do not produce ethanol and carbon dioxide. The accumulation of lactic acid is often associated with muscle cramps.
Analysis of Reason (R):
Correct. Yeast is a unicellular fungus that respires anaerobically. In the absence of oxygen, yeast cells convert pyruvate into Ethanol and Carbon Dioxide. This process is known as alcoholic fermentation and is widely used in the brewing and baking industries.
Conclusion:
Since the Assertion claims that human muscles produce ethanol (which is false) and the Reason correctly describes fermentation in yeast, the Assertion is false, and the Reason is true.
Key Takeaway:
Anaerobic respiration yields different products based on the organism: Lactic Acid in animal muscle cells and Ethanol + Carbon Dioxide in yeast cells.