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Solutions for Biology, Class 7, ICSE
Describe the different types of respiration that takes place in plants.
Depending upon the presence or absence of oxygen, respiration is of two types — aerobic respiration and anaerobic respiration.
Aerobic respiration — When the oxidation of food (glucose) takes place in the presence of oxygen, it is called aerobic respiration. In this process, glucose is completely oxidized to form carbon dioxide and water. It takes place in mostly higher animals and plants. In aerobic respiration, 38 ATP molecules are released from oxidation of one glucose molecule.
Glucose + Oxygen ⟶ Carbon dioxide + Water + Energy (38 ATP)
Anaerobic respiration — When the oxidation of food (glucose) takes place in the absence of oxygen, it is called anaerobic respiration. In this process, glucose is not completely oxidized to form carbon dioxide and water. Rather, it is oxidized to produce ethyl alcohol or lactic acid and 2 ATP molecules.
Glucose (in absence of oxygen) ⟶ Carbon dioxide + Ethyl alcohol + Energy (2 ATP)
How does exchange of gases take place through the stomata?
Each stoma has two bean-shaped cells called guard cells. The inner walls of the guard cells are thicker than the outer walls. When the guard cells are full of water, they swell and bulge outwards, opening the stomata. When the stomata is open, the exchange of gases takes place by the process of diffusion. Oxygen and water vapour leave the plant through the stomata while carbon dioxide enters through them.
When the guard cells lose water, they lose their turgidity closing the stomata. When the stomata is closed, no exchange of gases takes place through it.
How does respiration occur in the stems and roots?
The old and mature roots and hard woody stems of certain trees are covered by bark. The bark contains very tiny openings called lenticels. The lenticels enable the oxygen to reach the intercellular spaces of interior tissues and carbon dioxide to be released into the atmosphere. At the base of the lenticels are loosely arranged cells that allow the diffuse gases to pass through them.
Respiration also takes place through the roots of plants. Air is present in the spaces between the soil particles. The oxygen in this air is absorbed by root hairs present on the roots. From root hairs, it is supplied to all the parts of the roots. Carbon dioxide released during respiration is diffused out of the roots through the same root hairs.
Write the differences between respiration in plants and animals.
| Sl. No. | Respiration in Animals | Respiration in Plants. |
|---|---|---|
| 1. | Animals take in oxygen through lungs. | Plants take in oxygen through stomata, lenticels and the general surface of the roots. |
| 2. | Carbon dioxide is released as by-product in the process and is not taken back. | Carbon dioxide is released as a by-product in the process and is reabsorbed for photosynthesis. |
| 3. | The food and oxygen used for respiration are taken from outside. | The food and oxygen used for respiration are produced by the plants themselves. |
| 4. | The rate of respiration is very fast. | The rate of respiration is slow. |
How many ATP molecules are produced during aerobic respiration?
38 ATP molecules are produced during aerobic respiration.
What is absent during anaerobic respiration?
Oxygen is absent during anaerobic respiration.
What are the by-products of anaerobic respiration?
The by-products of anaerobic respiration are ethyl alcohol and carbon dioxide with 2 molecules of ATP.
What are guard cells?
Each stoma has two bean-shaped cells called guard cells. The opening and closing of stomata is regulated by change in turgidity of the guard cells.
What are pneumatophores?
Pneumatophores are the specialized roots of plants growing in salty and marshy area, that grow out of the surface of water. They have many pores on their surface to respire.
............... is the process in which glucose is oxidized in the presence of oxygen to release energy.
Respiration is the process in which glucose is oxidized in the presence of oxygen to release energy.
The glucose combines with oxygen to produce carbon dioxide, water and ............... ATP molecules.
The glucose combines with oxygen to produce carbon dioxide, water and 38 ATP molecules.
In ............... respiration, glucose is not completely oxidized.
In anaerobic respiration, glucose is not completely oxidized.
In anaerobic respiration, glucose is oxidized to form carbon dioxide, ............... and 2 ATP energy molecules.
In anaerobic respiration, glucose is oxidized to form carbon dioxide, ethyl alcohol and 2 ATP energy molecules.
In ..............., energy is released in the form of heat and light and not stored for future use.
In combustion, energy is released in the form of heat and light and not stored for future use.
aerobic and anaerobic respiration
| Sl. No. | Aerobic Respiration | Anaerobic Respiration |
|---|---|---|
| 1. | It takes place in the presence of oxygen. | It takes place in the absence or shortage of oxygen. |
| 2. | Complete oxidation of food takes place. | Incomplete oxidation of food takes place. |
| 3. | 38 ATP molecules are produced by the oxidation of one glucose molecule. | 2 ATP molecules are produced by the oxidation of one glucose molecule. |
| 4. | Its end products are carbon dioxide and water. | Its end products are ethyl alcohol and carbon dioxide. |
respiration and combustion
| Sl. No. | Respiration | Combustion |
|---|---|---|
| 1. | It occurs in the living cells. | It does not occur in the living cells. |
| 2. | It takes place at room temperature. | It takes place at high temperature. |
| 3. | It is a slow process. | It is a fast process. |
| 4. | Energy is released in several steps and stored as ATP. | Energy is released in the form of heat and light. |
| 5. | Enzymes are involved. | No enzyme is involved. |
| 6. | Conversion of carbohydrates to carbon dioxide and water occurs in many steps. | Carbon dioxide and water are produced in one step. |
stomata and lenticels
| Sl. No. | Stomata | Lenticels |
|---|---|---|
| 1. | Stomata are present in leaves and green stems. | Lenticels are present in mature stems, roots and fruits. |
| 2. | Stomata are active only during day time. | Lenticels are active both during day and night. |
| 3. | Stomata have guard cells and they can be opened and closed. | Lenticels do not have guard cells, they are always open. |
photosynthesis and respiration
| Sl. No. | Photosynthesis | Respiration |
|---|---|---|
| 1. | Food is synthesized by plants using carbon dioxide and water. | Food is oxidized using oxygen to release energy. |
| 2. | It takes place only in autotrophs. | It takes place in both autotrophs and heterotrophs. |
| 3. | It takes place only in the cells of green plants that have chloroplast. | It takes place in the mitochondria of all living cells of a plant. |
| 4. | It takes place only during the day time. | It takes place during day and night. |
| 5. | It requires carbon dioxide and water. | It requires glucose and oxygen. |
| 6. | Oxygen is released as a by-product. | Carbon dioxide and water are released as by-product. |
| 7. | It captures energy and stores it in sugars. | It releases the energy stored in sugars. |
The energy released during respiration is stored in energy-rich chemical substances called ............... .
The energy released during respiration is stored in energy-rich chemical substances called ATP (Adenosine Triphosphate).
The entire process of respiration takes place partially in cytoplasm and partially in ............... .
The entire process of respiration takes place partially in cytoplasm and partially in mitochondria.
In aerobic respiration, glucose is completely oxidized to form ............... and water.
In aerobic respiration, glucose is completely oxidized to form carbon dioxide and water.
Only ............... ATP molecules are released by the oxidation of 1 glucose molecule during anaerobic respiration.
Only two ATP molecules are released by the oxidation of 1 glucose molecule during anaerobic respiration.
When the guard cells lose water, they lose their turgidity and the stomata ............... .
When the guard cells lose water, they lose their turgidity and the stomata closes.
............... is a process that takes place in plants throughout the day. It is of ............... types. They are ............... respiration and ...............respiration. In ............... respiration, complete ............... of glucose takes place in the presence of ............... to release ..............., ............... and ............... ATP molecules. In ............... respiration, incomplete ............... takes place in the ............... of oxygen to release ..............., ............... and ...............ATP molecules.
Respiration is a process that takes place in plants throughout the day. It is of two types. They are aerobic respiration and anaerobic respiration. In aerobic respiration, complete oxidation of glucose takes place in the presence of oxygen to release carbon dioxide, water and 38 ATP molecules. In anaerobic respiration, incomplete oxidation takes place in the absence of oxygen to release ethyl alcohol, carbon dioxide and two ATP molecules.
Look at the pictures given below and answer the following questions:
| Sl. No. | Column A | Column B |
|---|---|---|
| 1. | aerobic respiration | found in the old and mature roots and hard woody stems |
| 2. | anaerobic respiration | roots that grow out of the surface of water |
| 3. | stomata | releases carbon dioxide, ethyl alcohol and 2 ATP molecules |
| 4. | lenticels | found in green leaves and stems |
| 5. | pneumatophores | releases carbon dioxide, water and 38 ATP molecules |
| Sl. No. | Column A | Column B |
|---|---|---|
| 1. | aerobic respiration | releases carbon dioxide, water and 38 ATP molecules |
| 2. | anaerobic respiration | releases carbon dioxide, ethyl alcohol and 2 ATP molecules |
| 3. | stomata | found in green leaves and stems |
| 4. | lenticels | found in the old and mature roots and hard woody stems |
| 5. | pneumatophores | roots that grow out of the surface of water |
Forests are called the lungs of the earth. Why?
As the lungs purify (oxygenate) the air we breathe, the plants purify the air of atmosphere by releasing oxygen and absorbing carbon dioxide. Thus, forests serve as lungs of the earth, cleaning and oxygenating the air.
The by-products of photosynthesis are
oxygen and glucose.
Reason — Photosynthesis is the process by which plants form food (glucose) and release oxygen.
How many ATP molecules are produced by the oxidation of 2 molecules of glucose?
76
Reason — Oxidation of one molecule of glucose produces 38 ATP molecules. So, two molecule of glucoses on oxidation will produce 38 x 2 = 76 ATP molecules.
In aerobic respiration, the by-products are
carbon dioxide, water and 38 ATP molecules
Reason — Glucose + Oxygen ⟶ Carbon dioxide + Water + Energy (38 ATP)
Cellular respiration in plants takes place in the
mitochondria
Reason — Cellular respiration in plants takes place in the mitochondria (power house of the cell)
Plants that grow in salty water have specialized roots called
pneumatophores
Reason — They are aerial roots that help in respiration.
During anaerobic respiration, complete oxidation of glucose takes place.
False
Corrected statement — During anaerobic respiration, incomplete oxidation of glucose takes place.
Respiration takes place only in the leaves of a plant.
False
Corrected statement — Respiration takes place in all parts of plant plant like leaves, stem, roots, etc.
When the guard cells are full of water, they swell and bulge outwards opening the stomata.
True
The exchange of gases takes place in the leaves by the process of diffusion.
True
In photosynthesis, no energy is released.
True