Question 15 Marks
Tell the difference between the following:
(a) Photosystem-1 and Photosystem-II
(b) Photo-respiration and photosynthesis.
(a) Photosystem-1 and Photosystem-II
(b) Photo-respiration and photosynthesis.
Answer
View full question & answer→(a) Photosystem-I and Photosystem-II
(b) Photorespiration and Photosynthesis
| Photosystem-I (PS-I) | Photosystem-II (PS-II) |
| 1. It contains 200-400 chlorophyll, 50 carotenoids, one molecule of reaction center (P700), one molecule Cyt. f plastocyanin (PC), reducing substance, two molecules Cyt. b6 and one or two molecules of ferredoxin (Fd) and Fe and Cu. | 1. It contains 200 chlorophyll, 50 carotenoids, one molecular reaction center (P680). Plastoquinone (PQ), Mn++, Cl- and Cyt. b6. |
| 2. PS-I is found on the outer surface of thylakoid. | 2. PS-II is found on the inner surface of thylakoid. |
| 3. In this, a strong reducing substance is released which reduces NADP+ to NADPH + H+. | 3. PS-II finally donates the electron to PSI, which reduces NADP. |
| 4. Molecular O2 is not released from PS-I. | 4. PS-II decomposes water and produces molecular O2. |
| 5. It participates in both cyclic and non-cyclic phosphorylation. | 5. Participates only in noncyclic phosphorylation. |
| Photorespiration | Photosynthesis |
| 1. Requires light. | 1. Requires light. |
| 2. Glycolate is used. | 2. CO2 and H2O are used. |
| 3. It occurs in some plants, like wheat, rice etc. | 3. Occurs in all green plants. |
| 4. This process is completed by peroxisome, chloroplast and mitochondria together. | 4. This process occurs only in chloroplast. |
| 5. Photorespiration intensifies as the concentration of O2 increases. | 5. The action is inhibited by excess O2. |
| 6. In this process hydrogen peroxide (H2O2) is formed. | 6. H2O2 is not formed. |
| 7. Phosphorylation process does not take place | 7. Photophosphorylation occurs. |