This set of Biology Multiple Choice Questions & Answers (MCQs) focuses on “Respiration in Plants”.
1. Where does the energy required to carry life processes come from?
Explanation: All the energy required for life processes is obtained by the oxidation of some macromolecules that we call as food. All living organisms need energy to carry out daily life activities.
2. Which of the following can synthesise their food?
a) Yellow plants
b) Green plants
Explanation: Only green plants and cyanobacteria can prepare their food, by the process of photosynthesis. They trap light energy and convert it into chemical energy that is stored in the bonds of carbohydrates.
3. What kind of organisms are fungi?
Explanation: Fungi are generally saprophytes which are dependent on dead and decaying matter. Animals are heterotrophic, i.e., they obtain food from plants directly (herbivores) or indirectly (carnivores).
4. In green plants, all the cells, tissues and organs carry out photosynthesis.
Explanation: In green plants, not all cells, tissues and organs photosynthesise, only cells containing chloroplasts, that are most often located in the superficial layers, carry out photosynthesis.
5. What is meant by cellular respiration?
a) Breakdown of water
b) Breakdown of air to consume energy
c) Breakdown of food materials to release energy
d) Breakdown of soil to release energy
Explanation: Cellular respiration is the mechanism of breakdown of food materials within the cell to release energy and the trapping of this energy for the synthesis of ATP.
6. Where does the photosynthesis take place in eukaryotes?
Explanation: Photosynthesis takes place within the chloroplasts in the eukaryotes whereas the breakdown of complex molecules to yield energy takes place in the cytoplasm and the mitochondria.
7. The breaking of which of the following bonds leads to release of energy?
a) P-P bonds
b) C-C bonds
c) N-N bonds
d) S-S bonds
Explanation: The breaking of the C-C bonds of complex compounds through oxidation within the cells, leads to the release of a considerable amount of energy. This process is known as respiration.
8. Which of the following compounds are not oxidised to release energy?
Explanation: Nucleic acids like DNA and RNA are never oxidised to release energy because these are integrated parts of the cell and they are used to carry or express different genes in the human beings which carry out different functions like the formation of proteins, fats and carbohydrates.
9. During oxidation within a cell, all the energy is released into a single step.
Explanation: During oxidation within a cell, all the energy contained in the respiratory substrate is not released in a single step because then all the energy would be lost in a single step and the cell would not be able to store the synthesised energy for its future use.
10. Which of the following acts as the energy currency of the cell?
Explanation: ATP or Adenosine Triphosphate acts as the energy currency of the cell. The energy which is released by the oxidation of respiratory substrates is stored in ATP so that we can use it for future purposes.
11. Which of the following is used as a precursor for the biosynthesis of other molecules?
a) Phosphorous substrate
b) Nitrogen substrates
c) Carbon skeletons
d) Sulphur skeletons
Explanation: Carbon skeletons are used as precursors for the biosynthesis of other biomolecules as the oxidation of these carbon skeletons leads to the formation of ATP which is stored by the cells to be utilised in various-energy requiring processes of the organisms.
12. Which of the following gases do plants require for respiration?
Explanation: Plants do not require CO2, N2 or water vapour for respiration. Like human beings, plants also require oxygen for respiration so that they can release CO2. It is through photosynthesis, that they require carbon dioxide and release oxygen in a very large amount.
13. By the use of which of the following structures, plants exchange gases?
Explanation: Plants, unlike animals, have no specialised organs for gaseous exchange but they use stomata and lenticels for this purpose. Plants can easily get along without any specialised respiratory organs.
14. Why plants can get along without the need for specialised respiratory organs?
a) It would be an extra expense
b) They don’t like it
c) Each plant part takes care of its own needs
d) Oxygen is easily available for all the parts of the plants
Explanation: There are several reasons why plants can get along without respiratory organs.
i. Each plant part takes care of its own gas-exchange needs
ii. Plants do not present great demands for gas exchange
iii. The distance that gases must diffuse is not large.
15. What are lenticels?
a) Openings on the surface of the bark
b) Openings on the surface of roots
c) Pores on leaves
d) Pores on stem
Explanation: In stems, the living cells are organised in thin layers inside and beneath the bark. They also have openings called lenticels. The cells in the interior are dead and only provide mechanical support.
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