NIOS Biology Intext Solutions Chapter 12
INTEXT QUESTIONS 12.1
1. How do plant and other organisms obtain energy for various activites such as growth?
The green Plants convert solar energy to chemical energy and store it in the form of complex organic molecules. During respiration, they are oxidised and a large amount of energy is released. This is stored as ATP. Plants use this ATP for metabolic activities.
2. Name the energy-rich molecule formed during respiration from food.
In the form of ATP
3. Give two differences between aerobic and anaerobic respiration.
| Aerobic Respiration | Anaerobic Respiration |
| 2. Leads to complete oxidation of the organic substrate. | 1. Takes place in the complete absence of oxygen. |
| 3. Takes place in lower organisms such as bacteria, fungi, and in higher animals under limiting conditions of oxygen (e.g., in muscles when oxygen present is insufficient). | 1. Takes place in the presence of oxygen. |
| 3. It is most common in higher organisms (both plants and animals). | 3. Takes place in lower organisms such as bacteria, fungi, and in higher animals under limiting conditions of oxygen (e.g. in muscles when oxygen present is insufficient). |
| 4. C6H12O6 → 6CO2 + 6H2O + 6O2 +38 ATP | 2. Incomplete oxidation of the organic substrate takes place. |
| 5. It takes place in the cytoplasm and mitochondria in eukaryotes and the plasma membrane in prokaryotes. | 5. Takes place in the cytoplasm. |
INTEXT QUESTIONS 12.2
1. Name the surfaces that help plants in taking up oxygen from the atmosphere.
Gaseous exchange takes place through the general body surface of the plants, through the stomata, and through the lenticels.
2. Name the process by which oxygen is taken up by the plants from the atmosphere.
Diffusion
3. Name the gases given out by plants during daytime and night.
Oxygen; carbon dioxide
4. Why do plants not have any special respiratory organs like animals? Give two reasons.
- (a) They have a large surface area to allow exchange of gases from and
- (b) their requirement of oxygen is much less.
INTEXT QUESTIONS 12.3
1. Why is pyruvic acid converted into alcohol or lactic acid during fermentation?
In the presence of O2, it is completely broken down to simple forms such as CO2 and H2O.
2Pyruvic acid + 6O2 → 6CO2 + 6H2O + 30ATP
(8ATP are obtained from glycolysis)
In the absence of O2, they carry out alcoholic fermentation.
2Pyruvic acid → 2Ethyl alcohol + 2CO2
2. Why is there less release of energy during anaerobic respiration?
This is because organic molecules are only partially oxidised in anaerobic respiration, and much of the energy remains in the end products, such as alcohol or lactic acid.
3. List the three phases of aerobic respiration of glucose. Where in the cell do these reactions take place?
Glycolysis in the cytosol, Krebs’ Cycle-matrix of mitochondria
E.T.C.-inner membrane of mitochondria
4. What is the role of O2 in aerobic respiration?
O2 acts as the terminal acceptor of electrons and H2, removed from the glucose molecule and is reduced to H2O.
5. Name the substrate and products of Krebs’ Cycle.
Substrate- Acetyl CoA
Product-2 CO2, 3 NADH2, 1 FADH2, 1 ATP
6. How do fatty acids enter Krebs’ Cycle?
Fatty Acid undergoes β-oxidation and produce acetyl-CoA. This can enter the Krebs’ Cycle
7. When the amount of CO2 uptake during photosysthesis is equal to the amount of CO2 generated through respiration, it is called …..
Compensation point.
8. What is amphibolic pathway?
The amphibolic pathway is the occurrence of both photosynthetic and respiratory pathways simultaneously, as seen in green plants. Here, the green plants carry out photosynthesis, during which CO2 and H2O are utilised in the presence of sunlight to synthesize starch and energy. At the same time, respiration breaks down glucose molecules by oxidising them to yield CO2, H2O, and energy.
INTEXT QUESTIONS 12.4
1. What is the R.Q. for carbohydrates and fats?
R.Q. is 1
2. What is the effect of high concentration of O2 on respiration?
The rate of respiration increases up to a point, and beyond this point, its rate of increase falls.
3. What is the ideal temperature for the process of respiration?
30-35°C
4. Define R.Q.
It is the ratio of the volume of CO2 evolved to the volume of O2 consumed in respiration. It gives us an idea of the kind of substrate used for respiration.
5. What is the limiting factor of respiration in dry seeds?
Water for the hydration of respiratory enzymes.
INTEXT QUESTIONS 12.5
1. Name the products that are formed when RUBP combines with O2. Name the enzyme that is responsible for this reaction.
Products are 1 P.G.A. and 1 Phosphoglycolate
2. Give one point of difference between respiration and photorespiration.?
| Respiration | Photorespiration |
| 1. Occurs in cytoplasm and mitochondria | 1. Occurs in the cytoplasm and mitochondria |
| 2. Substrate is glucose | 2. Substrate is RUBP |
| 3. ATP, CO2 and H2O are given out as products | 4. Takes place in C3 as well as C4 plants |
| 1. It involves 3 organelles: chloroplast, mitochondria peroxisome | 4. Takes place in green plants (C3-plants) |
| 5. Occurs at both day and night | 5. Takes place under high O2 and low CO2 and high temperature. Therefore occurs only during the day. |
| 6. Makes energy available for metabolic activities. | 3. The products are only CO2 and P.G.A., and no ATP is generated |
3. State the conditions under which photorespiration occurs?
- (a) Light
- (b) High concentration of O2
- (c) Low concentration of CO2
Additional Study Materials
- Chapter 06 Root system
- Chapter 07 Shoot system
- Chapter 08 Absorption, Transport, and Water Loss in Plants
- Chapter 09 Nutrition in plants – Mineral Nutrition
- Chapter 10 Nitrogen Metabolism
- Chapter 11 Photosynthesis
