UPSC Prelims 2013 Q50: Science & Technology – Biology
Consider the following minerals:
1. Calcium
2. Iron
3. Sodium
Which of the minerals given above is/are required by human body for the contraction of muscles?
- (a) 1 only
- (b) 2 and 3 only
- (c) 1 and 3 only
- (d) 1, 2 and 3
Answer: (d) 1, 2 and 3
Explanation
Minerals needed for the contraction of muscles
| Mineral | Needed for muscle contraction? (official key) | Role |
|---|---|---|
| 1. Calcium | Yes | Calcium ions let actin and myosin filaments slide over each other |
| 2. Iron | Yes | Part of myoglobin and haemoglobin, which bring oxygen to working muscle |
| 3. Sodium | Yes | Carries the nerve impulse that triggers contraction |
Other minerals and muscles:
| Mineral | Role |
|---|---|
| Potassium | Works with sodium to reset the muscle after an impulse |
| Magnesium | Helps the muscle relax |
Lack of minerals:
| Deficiency | Effect |
|---|---|
| Calcium | Muscle cramps and spasms |
| Iron | Anaemia, weakness, fatigue |
| Sodium | Cramps, weakness |
Answer: (d) 1, 2 and 3.
Why each option is right or wrong
- (a) Incorrect. Iron and sodium are also needed.
- (b) Incorrect. Calcium is the most direct requirement.
- (c) Incorrect. The official key also counts iron.
- (d) CORRECT. Calcium, iron and sodium are all required for muscle contraction.
Key point
Muscle contraction: calcium (actin-myosin sliding), sodium and potassium (nerve impulse), iron (oxygen through myoglobin).
Remember
Muscles need calcium, sodium and iron.
Common mistakes
- Leaving out iron, whose role through oxygen supply is indirect.
- Forgetting sodium's role in the nerve impulse.
- Thinking only calcium matters for muscles.
Exam tip
Signal (sodium), slide (calcium), supply (iron).
Sources
- NCERT Class XI — Biology (Locomotion and Movement: mechanism of muscle contraction)
- NCERT Class XI — Biology (Neural Control and Coordination)