Respiration in PlantsNEET Botany · Class 11 · NCERT Chapter 14

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• Click "Cristae". Note the folds: this is why mitochondria from heart muscle (very high energy demand) have many more cristae than a quiet skin cell.
• Click "Intermembrane space" to see H+ ions accumulate. The proton motive force = high H+ outside (here) vs low H+ in matrix.
• Click each F1 head (the small pink balls): this is where ATP is made. The F1 heads always face the matrix; this is why ATP is synthesised in the matrix and not in the intermembrane space.

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• Slide the tracker to step 5: cumulative ATP = -2 (we have only spent ATP so far). Slide to step 7: cumulative ATP = 0 (we have just broken even). Slide to step 10: cumulative ATP = +2 (the net yield).
• Click step 3 (PFK). This is the irreversible, committed step of glycolysis. Why is this evolutionarily important? (Hint: it makes regulation simple by gating one step.)
• Click step 6 (G3P dehydrogenase). This is the only step that produces NADH. Note that it happens TWICE per glucose (because of the 2 G3P), giving 2 NADH total.

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• Set turns = 2 (one glucose). Note: 6 NADH + 2 FADH2 + 2 ATP + 4 CO2. The 4 CO2 from Krebs + 2 CO2 from link reaction = 6 CO2 per glucose, matching the overall equation.
• Click step 5: this is where the only direct ATP / GTP of the Krebs cycle is made (substrate-level phosphorylation). All other ATP comes later via the ETC.
• Click step 6: succinate dehydrogenase is unique because it sits in the inner membrane (it is Complex II of the ETC). Its FADH2 hands electrons directly to ubiquinone.

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• Toggle to FADH2: notice that the Complex I proton arrow disappears (no H+ pumped at Complex II). This is why FADH2 yields only 2 ATP vs NADH's 3 ATP.
• Click each complex in order I → III → IV. Notice the H+ arrows go up (matrix → intermembrane space) at I, III, IV. Then click V (ATP synthase): the H+ arrow goes DOWN, and ATP is made.
• Click Complex IV: oxygen is the final electron acceptor. Without O2, electrons stop here. NADH and FADH2 build up. Krebs cycle stops. This is why anaerobic conditions kill aerobic respiration.

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• Toggle to "Alcoholic": notice the 2-step pathway (decarboxylation + reduction). Notice CO2 release in step 1. This is what makes bread rise.
• Toggle to "Lactic": notice the SINGLE step (just reduction). NO CO2. This is why curd / yoghurt does not bubble like beer does.
• Both pathways consume NADH (regenerate NAD+) but produce ZERO additional ATP beyond the 2 from glycolysis. Compare to aerobic respiration's 38 ATP, which is why aerobic life evolved.

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• Toggle to "NEET-key features": you see only the 4 most-tested distinctions (O2, site, end products, ATP yield). These are the highest-yield quiz triggers.
• Look at the ATP row: 38 vs 2. This 19x difference is why aerobic life evolved. Mitochondria are the engines that make this possible.
• Look at the "End product" row: anaerobic respiration is INCOMPLETE oxidation. Glucose still has chemical energy locked in lactate or ethanol; aerobic squeezes much more out of the same molecule.

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• Toggle between aerobic and fermentation. Notice the difference: 38 ATP vs 2 ATP for the same glucose. This is why aerobic life dominates.
• In aerobic mode: count where the 38 ATP come from. Glycolysis: 2 ATP (direct) + 2 NADH × 3 = 8. Link: 2 NADH × 3 = 6. Krebs: 2 ATP (direct) + 6 NADH × 3 + 2 FADH2 × 2 = 24. Total: 8 + 6 + 24 = 38.
• In fermentation mode: notice that NADH from glycolysis (+2) is consumed (-2) in fermentation. Net coenzyme yield is zero. The only ATP is from glycolysis itself.

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• Click "Carbohydrates" first: RQ = 6/6 = 1.0. Now toggle to "Fats": RQ ≈ 0.7. The reason fat RQ is less than 1.0 is fats need extra O2 to oxidise their many C-H bonds.
• Toggle to "Anaerobic": RQ = infinity. CO2 is still produced (from yeast pyruvate decarboxylase), but ZERO O2 is consumed (because the pathway is anaerobic).
• Toggle to "Organic acids": RQ > 1.0 (1.33 for malic acid). The molecule is so oxygenated already that it needs less external O2 than the CO2 it puts out.

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• Click "Acetyl CoA": it is the precursor for fatty acids (when you eat extra glucose, the carbohydrate is converted to acetyl CoA, which is then used to build fat). This is the metabolic basis of weight gain.
• Click "Alpha-ketoglutarate": it makes the glutamate amino acid family. In plants, it is also the precursor for chlorophyll. So a plant respires AND makes chlorophyll using respiratory intermediates.
• Click "Succinyl CoA": it is the precursor for ALL porphyrin pigments (heme, chlorophyll, cytochromes). Without it, there is no oxygen-carrying hemoglobin and no light-capturing chlorophyll.