Important Questions for Class 11 Biology-Respiration in Plants

For gaseous exchange, plants do not have a specialized system as seen in animals. Plant structures like lenticels and stomata carry out the gaseous exchange in plants. Living cells in plants have their surfaces exposed to the air. Life processes require energy that is obtained from oxidation of several macromolecules which is known as food. Through the process of photosynthesis, only cyanobacteria and plants can prepare their own food as they are capable of capturing sunlight and converting it into chemical energy which is accumulated in the bonds of carbohydrates such as sucrose, starch, and glucose. Read on to learn more about how plants respire.

Very Short Answer Type Questions

Q.1. How is the energy released and stored during oxidation of compounds in respiration?
A.1. The energy released is directly collected in ATP in the form of chemical bonds. ADP + IP + energy → ATP This bond is broken and utilized whenever required ATP → ADP + IP + energy
Q.2. What is ‘Energy Currency’. Name the substance in animals and plants that act as an energy currency.
A.2. Energy is required by every cell to function. Energy currency releases and stores energy as and when required in the cell. In both plants and animals, ATP is known as the energy currency.
Q.3. In man and yeast, when does anaerobic respiration take place?
A.3. In man, it occurs when there is a lack of oxygen during cellular respiration, hence pyruvic acid is reduced to lactic acid by the lactate dehydrogenase. In yeasts also it occurs in the absence of oxygen.
Q.4. On oxidation, which of these releases more energy? Organize them in an arranging order.
a) 1gm of fat
b) 1gm of protein
c) 1gm of glucose
d) 0.5gm of protein + 0.5gm of glucose
A.4. 1gm of fat releases most energy. The following is the ascending order: 1gm of glucose < 0.5 gm of protein + 0.5gm of glucose < 1gm of protein < 1gm of fat.
Q.5. Fo-F1 particles are involved in the synthesis of?
A.5. They are both present in the inner mitochondrial membrane and are involved in the synthesis of ATP which is the energy currency of the cell.
Q.6. What is the product of the following?
a) Aerobic glycolysis in skeletal muscle
b) Anaerobic fermentation in yeast
A.6. a) Pyruvic acid b) C2H5OH + CO2

Short Answer Type Questions

Q.1. Why is a person fed with glucose or a fruit juice instead of a cheese sandwich that might give more energy, when a person is feeling dizzy?
A.1. Glucose gives instant energy as it is absorbed and reaches the blood. Cheese sandwich, however, requires time to digest and absorb. As sick people need an immediate energy supply, they are fed with glucose or given fruit juice.
Q.2. Aerobic respiration has more efficiency. Justify.
A.2. In this process, a single molecule of glucose can yield up to 36 ATP molecules. In anaerobic respiration or fermentation, there are only 2 molecules of ATP from every molecule of glucose, which in comparison is lesser than aerobic respiration. Hence aerobic respiration is more efficient.
Q.3. The final product of glycolysis is pyruvic acid. Write the three metabolic fates of the pyruvic acid in anaerobic and aerobic conditions as seen in the diagram below.Glycolysis
A.3. Lactic acid – Formed by oxidation of pyruvic acid in skeletal muscles under anaerobic conditions. Ethanol – Formed by oxidation of pyruvic acid under anaerobic condition in yeasts Acetyl Co-A – Formed by the oxidation of pyruvic acid occurring within the mitochondria under aerobic conditions.
Q.4. Anaerobic respiration is observed in entities living such as human and angiosperms in aerobic conditions. Why?
A.4. In normal conditions in human beings, aerobic respiration takes place. In intense conditions such as heavy exercises, muscles require too much energy(ATP) hence consume more energy to be able to produce that energy which results in lack of oxygen thereby causing the muscle cells to make lactic acid through anaerobic respiration to meet their energetic needs. Under deficient conditions of oxygen, yeast cells carry out anaerobic respiration to form ethyl alcohol and carbon dioxide.
Q.5. State why the respiratory pathway is referred to as an amphibolic pathway.
A.5. Fatty acids and proteins are degraded to acetyl CoA to enter the respiratory pathway. Substances are withdrawn from the respiratory pathway during the synthesis of fats and proteins and are used in anabolism. Formation of substances is called anabolism and breakdown of substances is known as catabolism. Since the respiratory pathway is responsible for both catabolism and anabolism, it is known as the amphibolic pathway.

Long Answer Type Questions

Q.1. Explain the significance of Oxygen in aerobic respiration in the context of ETS.
A.1. The aerobic process of respiration occurs in the existence of oxygen and the function of oxygen is limited to the final phase of the process. Presence of oxygen is important as it drives the process by eliminating hydrogen from the system. Oxygen serves as the last hydrogen acceptor. In respiration, the energy of oxidation-reduction is used as opposed to the process of photophosphorylation where light energy is used for the generation of proton gradient that is required for phosphorylation. Hence it is called oxidative phosphorylation. Without oxygen, electrons cannot pass through the co-enzymes and in turn proton pump will not take place hence ATP will not be produced.
Q.2. What are some of the assumptions we make in the respiratory balance sheet? Are these valid enough to be applied to living systems? State comparisons between aerobic respiration and fermentation corresponding to respiration.
A.2. Following are the assumptions:

  • The sequential pathway that follows – TCA cycle, glycolysis, and ETS in the cytoplasm, mitochondrial matrix, and inner mitochondrial membrane respectively.
  • NADH, synthesized in glycolysis enters into ETC for phosphorylation
  • In the pathway, not one of the intermediates are utilized for the synthesis of compounds
  • Glucose forms the respiratory substrate

These assumptions do not apply to the living system as:

  • The pathways occur simultaneously and not one after the other
  • Utilization of ATP only when required
  • Rate of enzyme actions is regulated by several means

Listed below is the comparison between fermentation and aerobic respiration

Fermentation Aerobic respiration
It is the incomplete disintegration of glucose A complete breakdown of glucose
Oxidation of NADH to NAD+ is a slow process In aerobic respiration, it is a vigorous reaction
2 ATP molecules generated 38 ATP generated

Q.3. Explain Glycolysis. State where it occurs and its end products. In both aerobic and anaerobic respiration, determine the fate of these products.
A.3. It takes place in the cytoplasm of the cell and is seen in all living entities. In this, glucose goes through partial oxidation for the formation of pyruvic acid(2 molecules). It is obtained from sucrose in plants which is the resulting product of photosynthesis. Invertase converts sucrose into fructose and glucose which enter into the glycolytic pathway. These are phosphorylated to produce glucose-6-phosphate which isomerizes to generate fructose-6-phosphate. A sequence of 10 reactions regulated by different enzymes occurs in glycolysis to yield pyruvate from glucose. The chief product of glycolysis is pyruvic acid. The cellular need decides pyruvate’s metabolic fate. The three modes in which various cells manage pyruvic acid produced by glycolysis are – lactic acid fermentation, aerobic respiration, and alcoholic fermentation. Under anaerobic conditions in unicellular eukaryotes and prokaryotes, fermentation takes place. Kreb’s cycle or aerobic respiration is observed in entities for the complete oxidation of glucose into carbon dioxide and water which requires the supply of oxygen. Discover more about biology and concepts related to respiration in plants by registering at BYJU’S.

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