The sunlight energy used by green plants in photosynthesis is transformed into
- (a)chemical energy
- (b)physical energy
- (c)Both (A) and (B)
- (d)None of the above
Correct — A, chemical energy. In photosynthesis, chlorophyll traps radiant (light) energy from the Sun and uses it to build glucose from carbon dioxide and water. The light energy ends up stored in the chemical bonds of that glucose — i.e. it is converted into chemical energy. Plants (and later the animals that eat them) release this stored chemical energy during respiration.
- (b)physical energy — Photosynthesis stores energy in the chemical bonds of carbohydrate, not as some vague 'physical energy'. 'Physical energy' is not the recognised product of the light reactions.
- (c)Both (A) and (B) — Since the transformation is only into chemical energy, 'both' is wrong — physical energy is not produced.
- (d)None of the above — Wrong — a definite product, chemical energy, is formed, so 'none' cannot be correct.
Photosynthesis is an energy-conversion process: light energy is captured by the green pigment chlorophyll and transformed into chemical energy stored in glucose (C6H12O6). The overall reaction is 6CO2 + 6H2O + light energy -> C6H12O6 + 6O2. Respiration later reverses this, releasing the stored chemical energy for the cell to use.
The trap is the word 'physical'. Exams test whether you know the exact form of the stored energy — it is chemical (bond) energy, not heat, light or 'physical' energy. Anchor the chain: light energy -> chlorophyll -> chemical energy in glucose.
- Photosynthesis converts light (solar) energy into chemical energy stored in glucose.
- Chlorophyll is the pigment that absorbs light to drive the process.
- Site of photosynthesis: the chloroplast in green plant cells.
- Overall: 6CO2 + 6H2O + light -> glucose + 6O2; oxygen is released as a by-product.
- Choosing 'physical energy' or 'both' instead of chemical energy
- Confusing photosynthesis (stores energy) with respiration (releases energy)
MPPSC and UPSC ask this as a one-line energy-conversion fact or by matching the process to its organelle/product. Lock: light energy -> chemical energy (glucose), in the chloroplast.
Which one of the following is the process involved in photosynthesis?
- (a) Potential energy is released to form free energy
- (b) Free energy is converted into potential energy and stored
- (c) Food is oxidized to release carbon dioxide and water
- (d) Oxygen is taken in, and carbon dioxide and water vapour are given out
Answer(b) Free energy is converted into potential energy and stored
Same idea — photosynthesis converts the Sun's radiant (free) energy into stored chemical/potential energy in carbohydrate.
- practice — not a real PYQ
In green plants, photosynthesis takes place mainly in which cell organelle?
- (a)Mitochondrion
- (b)Chloroplast
- (c)Ribosome
- (d)Nucleus
Answer(b) Chloroplast — it contains chlorophyll and is the site of photosynthesis.
- practice — not a real PYQ
During photosynthesis, the trapped light energy is finally stored as chemical energy in:
- (a)water molecules
- (b)oxygen gas
- (c)glucose (carbohydrate)
- (d)soil minerals
Answer(c) glucose (carbohydrate) — its chemical bonds hold the stored energy.