Respiration Of Plants

Step 1: Understanding Substrate-Level Phosphorylation

Substrate-level phosphorylation (SLP) is a process in which a phosphate group is directly transferred from a high-energy substrate to ADP, forming ATP. This occurs in glycolysis and the Krebs cycle.

Step 2: Analyzing the Reactions

- 1,3-bisphosphoglyceric acid → 3-phosphoglyceric acid:
Substrate-level phosphorylation occurs here (ATP is generated).
- 3-phosphoglyceric acid → 2-phosphoglyceric acid:
This is a simple isomerization reaction and does not involve ATP formation.
- Phosphoenol pyruvate → Pyruvic acid:
ATP is generated via substrate-level phosphorylation.
- Succinyl CoA → Succinic acid:
ATP (or GTP) is generated in this step via substrate-level phosphorylation.
Thus, the reaction where substrate-level phosphorylation does not occur is option (B).

Step 1: Analyze the Diagram Labels (Standard Monocot Embryo):

• A (Top shield-shaped structure): This is the single cotyledon of the grass family, called the Scutellum.
• B (Region enclosed by sheath): The label points to the shoot tip region, which is the Shoot apex (plumule), enclosed by the coleoptile.
• C (Side flap): This represents the remains of the second cotyledon, called the Epiblast.
• D (Bottom tip): The label points to the protective covering at the very tip of the root (radicle). This is the Root cap (covered further by the coleorhiza).

Step 2: Evaluate Options:
Option (B) matches all labels correctly: A-Scutellum, B-Shoot apex, C-Epiblast, D-Root cap. Option (D) incorrectly uses the term "Mesoblast".

1. Photophosphorylation produces ATP and NADPH, not hexose sugar.
2. Hexose sugar is synthesized during the Calvin cycle (carbon fixation).
3. Proton gradient → ATP synthesis, C3 plants → 3-PGA, PEP carboxylase → OAA are all correct.
4. Hence incorrect match is (3) Photophosphorylation - Hexose sugar synthesis.

Ubiquinone (Coenzyme Q) is a lipid-soluble electron carrier in the mitochondrial electron transport chain. It transfers electrons: - From Complex I (NADH dehydrogenase) to Complex III (cytochrome bc1). - From Complex II (succinate dehydrogenase) to Complex III. It does not interact with Complex IV directly; cytochrome c carries electrons from III to IV. Therefore, the correct pairs are I & II.

1. Photophosphorylation produces ATP and NADPH, not hexose sugar.
2. Hexose sugar is synthesized during the Calvin cycle (carbon fixation).
3. Proton gradient → ATP synthesis, C3 plants → 3-PGA, PEP carboxylase → OAA are all correct.
4. Hence incorrect match is (3) Photophosphorylation - Hexose sugar synthesis.