Multiple Choice Questions
Question 1
Carbohydrates are stored by plants in the form of:
- Starch
- Proteins
- Fats
- Glucose
Answer
Starch
Reason — Glucose is formed in leaves very rapidly during the photosynthesis and it cannot be transported to other parts with the same rapidity. So, several molecules of glucose join together to form insoluble starch for temporary storage.
Question 2
Stomata are present on the surface of:
- Leaves
- Roots
- Stem
- Flower petals
Answer
Leaves
Reason — Stomata are present on the surface of leaves to facilitate exchange of gases between the leaf and the atmosphere.
Question 3
Which one of the following is the immediate end-product of photosynthesis?
- Fructose
- Glucose
- Cellulose
- Lactose
Answer
Glucose
Reason — Fructose, Cellulose and lactose are polymers of glucose.
Short Answer Questions
Question 1
Why do leaves generally look green?
Answer
Leaves generally look green because of the presence of chlorophyll, a pigment that imparts green colour to leaves.
Question 2
Which four of the following are needed for photosynthesis in a leaf?
- Carbon dioxide
- Oxygen
- Nitrates
- Water
- Chlorophyll
- Soil
- Light
Answer
Following are the four things which are needed for photosynthesis in a leaf:
- Carbon dioxide
- Water
- Chlorophyll
- Light
Question 3
What is the source of energy for photosynthesis?
Answer
The source of energy for photosynthesis is Sunlight.
Question 4
Which gas is taken in and which one is given out by a green leaf in bright sunlight?
(i) Taken in: ............... (ii) Given out: ...............
Answer
(i) Taken in: Carbon dioxide (ii) Given out: Oxygen
Question 5
Suppose we compare the leaf with a factory, match the items in Column A with those in Column B.
| Sl. No. | Column A | Column B |
|---|---|---|
| 1. | Cells in the leaf | Raw materials |
| 2. | Chloroplast | Power |
| 3. | Sunlight | Machinery |
| 4. | Oxygen and water | End product |
| 5. | Carbon dioxide and water | By product |
| 6. | Glucose | Work room |
Answer
| Sl. No. | Column A | Column B |
|---|---|---|
| 1. | Cells in the leaf | Work room |
| 2. | Chloroplast | Machinery |
| 3. | Sunlight | Power |
| 4. | Oxygen and water | By product |
| 5. | Carbon dioxide and water | Raw materials |
| 6. | Glucose | End product |
Question 6
State whether the following statements are True or False:
(i) Green plants prepare their food by using two raw materials, oxygen and water.
(ii) The chlorophyll enables the plants to use light energy.
(iii) The free oxygen in the atmospheric air is the result of photosynthesis.
(iv) Photosynthesis occurs only in chlorophyll-containing parts of the plant.
Answer
(i) False
Corrected Statement — Green plants prepare their food by using two raw materials; Carbon dioxide and water.
(ii) True
(iii) True
(iv) True
Question 7
Differentiate between aerobic and anaerobic respiration. Write the overall chemical equations of the two kinds of respiration in plants.
(i) Aerobic: ...............
(ii) Anaerobic: ...............
Answer
| Sl. No. | Aerobic Respiration | Anaerobic Respiration |
|---|---|---|
| 1. | It utilizes oxygen. | It does not utilize oxygen. |
| 2. | Food molecules (glucose) completely break down. | Food molecules (glucose) partially break down. |
| 3. | Carbon dioxide and water are formed. | Ethanol along with carbon dioxide (in plants) and lactic acid (in animals) are formed. |
| 4. | More energy is released (38 ATP molecules). | Less energy is released (2 ATP molecules). |
Chemical equations of the two kinds of respiration in plants are:
(i) Aerobic:
Glucose + Oxygen Carbon dioxide + water + Energy (38 ATP)
(ii) Anaerobic:
Glucose Ethanol + Carbon dioxide + Energy (2 ATP)
Question 8
Explain how photosynthesis is different from respiration.
Answer
The differences between Photosynthesis and Respiration are explained below:
| Sl. No. | Photosynthesis | Respiration |
|---|---|---|
| 1. | Food is synthesized. | Food is broken down. |
| 2. | Oxygen is released as a by-product. | Carbon dioxide is released as a by-product. |
| 3. | Occurs in plant cells containing chlorophyll. | Occurs in all cells of both plants and animals. |
| 4. | Occurs only during the day. | Occurs both during the day and the night. |
Question 9
Do the plants respire all day and night or only during the day? Give reasons.
Answer
Plants respire all day and night as plants require a constant supply of energy for all the different processes that go on inside the cells of the plant body. Energy is required for the growth of the plant, for root cells to penetrate the soil and absorb water and minerals and so many other such activities. Thus, Respiration occurs continuously in plants, during both day and night.
Question 10
What happens to the energy liberated during respiration?
Answer
The energy liberated during respiration is utilized for all the different processes that go on inside the cells of the plant body. Energy is required for the growth of the plant, for root cells to penetrate the soil and absorb water and minerals.
Long Answer Questions
Question 1
In order to carry out photosynthesis, what are the substances that a plant must take in? Also mention their sources.
Answer
In order to carry out photosynthesis, the substances that a plant must take in are Carbon dioxide and Water. Photosynthesis also require the presence of Chlorophyll and Sunlight.
Following are their sources:
- Carbon dioxide — Atmosphere
- Water — Soil
- Sunlight — Sun
- Chlorophyll — contained in the leaves.
Question 2
What is the role of chlorophyll in photosynthesis?
Answer
Chlorophyll is found in mesophyll cells of leaf, inside the plastids called chloroplast. Chlorophyll is very important as it absorbs the sunlight which provides energy for the process of photosynthesis. This energy is used to split water molecules (H2O) into hydrogen ions (H+) and hydroxyl ions (OH-). Oxygen from the hydroxyl ion is released into the air and hydrogen ions combine with carbon dioxide to form glucose.
Question 3
Do plants need oxygen? If so, what is its source?
Answer
Plants need oxygen for respiration. The source of oxygen is atmosphere.