NCERT Class 10 Science — Chapter 1: Life Processes

mcqeasy

The accumulation of which compound in muscle cells leads to cramps during sudden physical activity or anaerobic respiration?

Official previous-year question

Verified 1 Aug 2026.

Options

AAcetone
BLactic acid
CMethane
DEthanol

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Solution

The correct option is Lactic acid.

Explanation

Cellular respiration is the biochemical process by which cells break down glucose to release energy. While this typically occurs in the presence of oxygen (aerobic respiration), muscle cells can switch to anaerobic respiration when oxygen supply is insufficient to meet the energy demand.

Analysis of the Process:

Glycolysis: The first step of respiration involves breaking down glucose (a 6-carbon molecule) into pyruvate (a 3-carbon molecule) within the cytoplasm.
Anaerobic Respiration in Muscles: During sudden physical activity, the oxygen supply to muscle cells may be inadequate. In this situation, pyruvate is converted into lactic acid (a 3-carbon molecule) and energy.
Cause of Cramps: The rapid accumulation of lactic acid in the muscle tissues leads to acidity and fatigue, resulting in muscle cramps.
Comparison with Other Options:
- Ethanol: This is produced during anaerobic respiration (fermentation) in yeast, along with carbon dioxide, not in human muscles.
- Acetone and Methane: These are not byproducts of glucose metabolism in human muscle cells.

Key Takeaway: Muscle cramps occur due to the accumulation of lactic acid, which is produced when muscle cells break down glucose anaerobically due to a lack of oxygen.

Your note

More from Chapter 1: Life Processes

Which enzyme, present in saliva and pancreatic juice, is primarily responsible for the breakdown of starch into simpler sugars?

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Which hair-like structures lining the upper respiratory tract help in filtering air by trapping dust and particles?

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In the circulatory system of fishes, the heart is characteristically composed of how many chambers?

easy

With reference to maintenance functions in organisms, consider the following statements: 1. The transfer of energy source from outside to inside is referred to as respiration. 2. These processes require energy sourced from outside the body. 3. All organisms obtain energy directly from sunlight. Which of the statements given above is/are correct?

medium

Consider the following in the context of body design and exchange with the environment: 1. In single-celled organisms, the entire surface can handle intake and waste removal. 2. In multicellular organisms, simple diffusion is sufficient for all cells. 3. Increased body size and complexity necessitate specialised organs. Which of the statements given above are correct?

hard

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The correct option is Lactic acid.

Explanation

Analysis of the Process:

Glycolysis: The first step of respiration involves breaking down glucose (a 6-carbon molecule) into pyruvate (a 3-carbon molecule) within the cytoplasm.
Anaerobic Respiration in Muscles: During sudden physical activity, the oxygen supply to muscle cells may be inadequate. In this situation, pyruvate is converted into lactic acid (a 3-carbon molecule) and energy.
Cause of Cramps: The rapid accumulation of lactic acid in the muscle tissues leads to acidity and fatigue, resulting in muscle cramps.
Comparison with Other Options:
- Ethanol: This is produced during anaerobic respiration (fermentation) in yeast, along with carbon dioxide, not in human muscles.
- Acetone and Methane: These are not byproducts of glucose metabolism in human muscle cells.

Key Takeaway: Muscle cramps occur due to the accumulation of lactic acid, which is produced when muscle cells break down glucose anaerobically due to a lack of oxygen.