What is Respiration?
Respiration is the process of oxidation of food molecules to release energy in the form of ATP.
General Equation
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP)
Why is Respiration Important?
Releases energy for life processes
Supports growth and development
Powers active transport
Essential for cell division
Maintains metabolism
Types of Respiration
1. Aerobic Respiration
Occurs in presence of oxygen
Complete oxidation of glucose
Produces maximum ATP
2. Anaerobic Respiration
Occurs without oxygen
Partial oxidation of glucose
Produces less ATP
Example
Yeast: Glucose → Ethanol + CO₂ + Energy
Glycolysis
Definition
Breakdown of glucose into pyruvate.
Site
Cytoplasm
Important Facts
First step of respiration
Occurs in all living cells
Does not require oxygen
End Products
2 Pyruvate
2 ATP (Net gain)
2 NADH
NCERT Point
Glycolysis is also known as EMP pathway.
Fate of Pyruvate
Pyruvate can undergo three pathways:
1. Lactic Acid Fermentation
Muscle cells
Pyruvate → Lactic Acid
2. Alcoholic Fermentation
Yeast
Pyruvate → Ethanol + CO₂
3. Aerobic Respiration
Pyruvate enters mitochondria.
Krebs Cycle (Citric Acid Cycle)
Site
Mitochondrial Matrix
Starting Molecule
Acetyl CoA
Products from One Acetyl CoA
3 NADH
1 FADH₂
1 ATP
2 CO₂
NCERT Important Line
Krebs cycle was discovered by Hans Krebs.
Electron Transport System (ETS)
Site
Inner mitochondrial membrane
Components
Complex I
Complex II
Complex III
Complex IV
Function
Transfers electrons and generates ATP.
Final Electron Acceptor
Oxygen
Product Formed
Water
Oxidative Phosphorylation
ATP formation during ETS is called oxidative phosphorylation.
ATP Synthase
Responsible for ATP production.
NCERT Point
ATP synthase is located on the inner mitochondrial membrane.
ATP Yield
Aerobic Respiration
One glucose molecule produces approximately:
36–38 ATP
Anaerobic Respiration
Only:
2 ATP
Amphibolic Pathway
Respiration is called an amphibolic pathway because it participates in:
Catabolism
Anabolism
NEET Favorite Concept
Why is respiration called amphibolic?
Because it acts in both breakdown and synthesis pathways.
Respiratory Quotient (RQ)
Formula
RQ = CO₂ Released / O₂ Consumed
Carbohydrates
RQ = 1
Fats
RQ < 1
Organic Acids
RQ > 1
Mitochondria: Powerhouse of Cell
Structure
Outer membrane
Inner membrane
Cristae
Matrix
Function
ATP production
NCERT Point
Cristae increase surface area for ATP generation.
Aerobic vs Anaerobic Respiration
Feature
Aerobic
Anaerobic
Oxygen
Required
Not Required
ATP Yield
36–38
2
Oxidation
Complete
Partial
End Products
CO₂ + H₂O
Ethanol/Lactic Acid
Most Important NCERT Points
✔ Glycolysis occurs in cytoplasm.
✔ Krebs cycle occurs in mitochondrial matrix.
✔ ETS occurs in inner mitochondrial membrane.
✔ Oxygen is final electron acceptor.
✔ ATP synthase produces ATP.
✔ Respiration is amphibolic.
✔ RQ for carbohydrates is 1.
NEET PYQ Practice Questions
Q1. Glycolysis occurs in:
A. Nucleus
B. Cytoplasm
C. Mitochondria
D. Ribosome
✅ Answer: B. Cytoplasm
Q2. Final electron acceptor in ETS is:
A. Carbon dioxide
B. NADH
C. Oxygen
D. FAD
✅ Answer: C. Oxygen
Q3. Krebs cycle occurs in:
A. Cytoplasm
B. Chloroplast
C. Mitochondrial Matrix
D. Nucleus
✅ Answer: C. Mitochondrial Matrix
Q4. Respiratory Quotient of carbohydrates is:
A. 0.7
B. 0.9
C. 1
D. 1.5
✅ Answer: C. 1
Q5. ATP synthase is located in:
A. Outer membrane
B. Ribosome
C. Inner mitochondrial membrane
D. Matrix
✅ Answer: C. Inner mitochondrial membrane
Final Revision Strategy for NEET
Focus On
Glycolysis steps
Krebs cycle products
ATP calculation
ETS diagram
Respiratory Quotient
Aerobic vs Anaerobic comparison
Conclusion
Respiration in Plants is a high-yield NEET chapter that often contributes direct questions from NCERT. Master glycolysis, Krebs cycle, ETS, ATP production, and RQ concepts to secure easy marks in Biology.
Read NCERT line by line, revise diagrams, and solve PYQs regularly for maximum NEET success. 🚀
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