Respiration in Plants for NEET UG 2026: Complete Notes, Tricks, MCQs & Revision Guide

1. MOST IMPORTANT CONCEPTS (NEET DIRECT QUESTIONS)

Definition

Respiration = Oxidation of food → Energy release (ATP)

Occurs in:

•    Cytoplasm → Glycolysis
•    Mitochondria → Krebs Cycle + ETS

Overall Equation (VERY IMPORTANT)

C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + Energy

 ATP Yield (FREQUENT MCQ)

Process	ATP
Glycolysis	2 (net)
Crebs Cycle	2
ETS	34 (net)
Total	38 ATP

⚠️ NEET Trick: Sometimes they ask theoretical vs actual ATP → Answer: theoretical = 38

Locations (VERY IMPORTANT: MATCH THE FOLLOWING)

•  Glycolysis → Cytoplasm
•  Krebs Cycle → Mitochondrial matrix
•  ETS → Inner mitochondrial membrane

2. GLYCOLYSIS (HIGH WEIGHTAGE)

Key Points

•  Occurs in all living organisms
•  Anaerobic process
•  Glucose → 2 Pyruvate

Important Outputs:

•  2 ATP (net)
•  2 NADH

MOST ASKED POINTS

•  First ATP used → Glucose → Glucose6phosphate
•  NADH formed at → PGAL → BPGA

MNEMONIC (Steps Memory Trick)

“Goodness Gracious Father Franklin Did Go By Picking Pumpkins to Prepare Pies”

(Glycolysis intermediates sequence)

3. FERMENTATION (VERY SCORING)

 Types:

1. Alcoholic Fermentation (Yeast)

•     Product → Ethanol + CO₂

2. Lactic Acid Fermentation

•     Product → Lactic Acid (Muscle)

NEET TRAPS:

 ATP produced = Only 2 ATP

 Occurs in:

•    Yeast
•    Muscle cells (low O₂)

Important Concept:

•  NADH → NAD⁺ regeneration (VERY IMPORTANT MCQ)

4. AEROBIC RESPIRATION

Steps:

1. Glycolysis
2. Link Reaction (Pyruvate → Acetyl CoA)
3. Krebs Cycle
4. ETS

Link Reaction (NEET FAVOURITE)

 Pyruvate → Acetyl CoA

 Releases:

•    CO₂
•    NADH

5. KREBS CYCLE (VERY IMPORTANT)

Key Outputs (Per Glucose):

•  2 ATP (GTP)
•  6 NADH
•  2 FADH₂
•  4 CO₂

Mnemonic:

“Citrate Is Krebs Starting Substrate For Making Oxaloacetate.”

(Citrate → Isocitrate → αKG → SuccinylCoA → Succinate → Fumarate → Malate → OAA)

6. ETS (ELECTRON TRANSPORT SYSTEM)

MOST SCORING TOPIC

 Key Points:

•  Location → Inner mitochondrial membrane
•  Oxygen = Final electron acceptor

ATP Yield:

•  NADH → 3 ATP
•  FADH₂ → 2 ATP

NEET TRAP:

Without oxygen → ETS stops → entire respiration stops

7. RESPIRATORY QUOTIENT (RQ)

 Formula:

RQ = \frac{CO_2\ released}{O_2\ consumed}

Values:

 NEET TRICK:

•  RQ < 1 → Fat metabolism
•  RQ > 1 → Organic acids

8. MOST COMMON MISTAKES (VERY IMPORTANT)

1. ❌ Thinking glycolysis needs oxygen

   ✔️ It is anaerobic

2. ❌ Confusing ATP count (net vs gross)

   ✔️ Net ATP = 2

3. ❌ Forgetting the location of processes
4. ❌ Mixing fermentation & aerobic respiration
5. ❌ Ignoring NADH role

9. HIGH-YIELD COMPARISON TABLE

Feature	Aerobic	Anaerobic
Oxygen	Required	Not Required
ATP	38	2
End Product	Co2 + H20(net)	Ethanol/Lactic Acid
Total	38 ATP

10. SUPER SHORT REVISION TRICKS

•  “Glyco = Cytoplasm”
•  “Krebs = Matrix”
•  “ETS = Membrane”
•  “38 ATP = Full respiration”
•  “2 ATP = Survival mode”

11. NEET LEVEL ANALYTICAL QUESTIONS

 Q1. If oxygen supply stops, which process stops first?

✔️ Answer: ETS

👉 Because O₂ is the final electron acceptor

 Q2. Net ATP in fermentation?

✔️ Answer: 2 ATP

Q3. Which step produces NADH in glycolysis?

✔️ Answer: PGAL → BPGA

Q4. RQ = 0.7 indicates?

✔️ Answer: Fat metabolism

Q5. Where is ATP synthase located?

✔️ Answer: Inner mitochondrial membrane

FINAL EXAM STRATEGY

Focus 80/20 Rule:

•  Glycolysis → 100% prepare
•  ETS → HIGH PRIORITY
•  RQ → Direct question
•  ATP count → Must revise

LAST MINUTE REVISION (1 LINE)

Glucose → Pyruvate → Acetyl CoA → Krebs → ETS → 38 ATP