The gaseous product of a process in plants is a requirement for another vital process that releases energy. Given below are four combinations of the process and product. Identify the correct answer.
- (a)Respiration and Nitric oxide
- (b)Transpiration and Water vapour
- (c)Photosynthesis and Oxygen
- (d)Germination and Carbon dioxide
Correct — C, Photosynthesis and Oxygen. Photosynthesis produces oxygen as its gaseous product. That oxygen is exactly what respiration — the energy-releasing process — needs to break down glucose and release energy. So the gaseous product (oxygen) of one process (photosynthesis) is the requirement of the other vital, energy-releasing process (respiration), which the clue in the question points to.
- (a)Respiration and Nitric oxide — Respiration is itself the energy-releasing process, not the supplier, and its gaseous product is carbon dioxide, not nitric oxide.
- (b)Transpiration and Water vapour — Transpiration releases water vapour, but water vapour is not the gas consumed by an energy-releasing process — respiration needs oxygen.
- (d)Germination and Carbon dioxide — Germination is not a gas-producing 'process' feeding energy release; carbon dioxide is a product of respiration, not the gas that a plant burns to release energy.
Photosynthesis and respiration are complementary. In photosynthesis, plants use carbon dioxide and water with light energy to make glucose and release oxygen. In respiration, cells use that oxygen to break down glucose and release energy (as ATP), giving out carbon dioxide and water. The oxygen output of one is the oxygen input of the other.
The question describes 'a gaseous product needed by an energy-releasing process' — the energy-releasing process is respiration, and the gas it needs is oxygen, which photosynthesis makes. Spotting that respiration (not photosynthesis) is the energy-releaser, and that its required gas is oxygen, points straight to option (c).
- Photosynthesis: CO2 + water + light energy → glucose + oxygen.
- Respiration: glucose + oxygen → energy (ATP) + CO2 + water.
- Oxygen released by photosynthesis is the gas required for aerobic respiration.
- Respiration is the energy-releasing process; photosynthesis is energy-storing.
- Thinking respiration is the 'supplier' — it is the energy-releasing consumer of oxygen.
- Confusing the gases: photosynthesis releases O2 and takes in CO2; respiration does the reverse.
Asked by linking a process to its gaseous product, or by contrasting the inputs and outputs of photosynthesis and respiration.
Consider the following: 1. Photosynthesis 2. Respiration 3. Decay of organic matter 4. Volcanic action. Which of the above add carbon dioxide to the carbon cycle on Earth?
- (a) 1 and 4 only
- (b) 2 and 3 only
- (c) 2, 3 and 4 only
- (d) 1, 2, 3 and 4
Answer(c) 2, 3 and 4 only
Same concept — the complementary gas exchange of photosynthesis and respiration. Photosynthesis removes CO2 (and releases O2) while respiration releases CO2 (and consumes O2), the exact contrast this NDA question rests on.
- practice — not a real PYQ
During photosynthesis, the gas released by green plants is
- (a)Carbon dioxide
- (b)Nitrogen
- (c)Oxygen
- (d)Hydrogen
Answer(c) Oxygen — a product of the light reactions of photosynthesis.
- practice — not a real PYQ
Aerobic respiration in cells requires which gas?
- (a)Carbon dioxide
- (b)Oxygen
- (c)Nitrogen
- (d)Methane
Answer(b) Oxygen — used to break down glucose and release energy.