(A) How is the movement of leaves of a sensitive plant different from the downward movement of the roots? OR (B) There is a hormone which regulates carbohydrate, protein and fat metabolism in our body. Name the hormone and the gland which secretes it. Why is it important for us to have iodised salt in our diet?

Q: (A) How is the movement of leaves of a sensitive plant different from the downward movement of the roots? OR (B) There is a hormone which regulates carbohydrate, protein and fat metabolism in our body. Name the hormone and the gland which secretes it. Why is it important for us to have iodised salt in our diet?

(A) The movement of leaves of a sensitive plant (*Mimosa pudica*) is a **nastic movement**, which is growth-independent and occurs rapidly due to changes in turgor pressure in response to touch. In contrast, the downward movement of roots is a **tropic movement** (specifically positive geotropism), which is growth-dependent and occurs slowly in response to gravity. OR (B) The hormone is **Thyroxin**, and it is secreted by the **Thyroid gland**. It is important to have iodised salt in our diet because iodine is essential for the synthesis of thyroxin. Thyroxin regulates carbohydrate, protein, and fat metabolism in the body to provide the best balance for growth. Its deficiency can lead to Goitre, characterized by a swollen neck.

Chemical Reactions and Equations

Exothermic Processes and Metabolism

Official Answer

(A) The movement of leaves of a sensitive plant (Mimosa pudica) is a nastic movement, which is growth-independent and occurs rapidly due to changes in turgor pressure in response to touch. In contrast, the downward movement of roots is a tropic movement (specifically positive geotropism), which is growth-dependent and occurs slowly in response to gravity.

(B) The hormone is Thyroxin, and it is secreted by the Thyroid gland. It is important to have iodised salt in our diet because iodine is essential for the synthesis of thyroxin. Thyroxin regulates carbohydrate, protein, and fat metabolism in the body to provide the best balance for growth. Its deficiency can lead to Goitre, characterized by a swollen neck.

Nastic movementTropic movementThyroxinThyroid glandIodineMetabolism

Marking Scheme

11 mark for distinguishing between growth-independent (nastic) and growth-dependent (tropic) movements.
20.5 mark for naming Thyroxin and Thyroid gland.
30.5 mark for explaining the importance of iodine (synthesis of thyroxin/prevention of goitre).

Hint

For (A), consider whether the movement involves growth. For (B), recall the gland located in the neck region.

Quick Oral Answer

Why is respiration called an exothermic reaction? Because energy is released during the process as glucose is oxidized.

Analysis & Explanation

The text links metabolism to chemical reactions, specifically mentioning that respiration is an exothermic process where glucose ( $C_6H_{12}O_6$ ) combines with oxygen to provide energy ( $C_6H_{12}O_6(aq) + 6O_2(aq) ightarrow 6CO_2(aq) + 6H_2O(l) + ext{energy}$ ). Hormones like thyroxin act as chemical messengers that regulate the rate of these metabolic chemical reactions. Plant movements, while physical in appearance, are driven by underlying chemical and electrochemical changes in cells.

Common Mistakes

1Confusing geotropism with phototropism.
2Spelling 'Thyroxin' or 'Thyroid' incorrectly.
3Forgetting to mention that plant leaf movement is growth-independent.

Interesting Facts

The 'drooping' of sensitive plant leaves happens in less than a second, which is one of the fastest movements in the plant kingdom.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2024?

This question carries 2 marks in the CBSE Class 10 Science 2024 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Chemical Reactions and Equations" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Exothermic Processes and Metabolism" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2024 paper?

This is a Very Short Answer question from Section B in the CBSE Class 10 Science 2024 paper.