Question

Choose the equation of reaction that correctly represents anaerobic respiration in muscles:

• A. Glucose $\rightarrow$ Pyruvate $\xrightarrow{\text{Absence of O}_2}$ Ethanol + CO$_2$ + Energy
• B. Glucose $\xrightarrow{\text{O}_2}$ Pyruvate $\xrightarrow{\text{O}_2}$ Energy
• C. Glucose $\xrightarrow{\text{O}_2}$ Pyruvate $\xrightarrow{\text{Lack of oxygen}}$ Ethanol + Energy
• D. Glucose $\rightarrow$ Pyruvate $\xrightarrow{\text{Lack of oxygen}}$ Lactic acid + Energy

Hint:

Anaerobic respiration in muscles → Lactic acid formation. Yeast → Ethanol, Humans → Lactic acid.

Answer 1

The Correct Option is D

Concept: Anaerobic respiration is the breakdown of glucose in the absence of oxygen. In human muscle cells, this process leads to the formation of lactic acid. Explanation:

• During intense exercise, oxygen supply to muscles becomes insufficient.
• Glucose is first converted into pyruvate.
• In the absence of oxygen, pyruvate is converted into lactic acid with release of a small amount of energy.

Correct Reaction: \[ \text{Glucose} \rightarrow \text{Pyruvate} \xrightarrow{\text{Lack of oxygen}} \text{Lactic acid} + \text{Energy} \] Why Other Options Are Incorrect:

• (A) Ethanol formation occurs in yeast, not in human muscles.
• (B) Represents aerobic respiration (presence of oxygen).
• (C) Ethanol formation again applies to yeast fermentation.

Conclusion: In human muscles, anaerobic respiration produces lactic acid and energy in the absence of oxygen.