Respiration Notes – Complete Biology Notes for OTET, CTET, OSSTET, B.Ed & Competitive Exams

RESPIRATION – COMPLETE BIOLOGY NOTES

Biology Study Material
Topic: Respiration
Useful for OTET, CTET, OSSTET, B.Ed, Junior Teacher, Constable and other competitive examinations.

1. Meaning of Respiration

Respiration is the biochemical process of breaking down food to release energy. This energy is stored in the form of ATP (Adenosine Triphosphate).

• Glucose is the main respiratory substrate.
• ATP is called the energy currency of the cell.
• Respiration occurs in all living cells.

2. Types of Respiration

A. Aerobic Respiration

• Occurs in the presence of oxygen.
• Complete breakdown of glucose takes place.
• Produces carbon dioxide, water and energy.
• Glycolysis occurs in cytoplasm; later stages occur in mitochondria.

B. Anaerobic Respiration

• Occurs without oxygen.
• Incomplete breakdown of glucose takes place.
• Produces less energy.
• Occurs in the cytoplasm.

3. Equation of Respiration

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy

Anaerobic respiration in yeast: Glucose → Ethanol + Carbon dioxide + Energy.

In human muscles: Glucose → Lactic acid + Energy.

4. Steps of Cellular Respiration

1. Glycolysis

• Occurs in the cytoplasm.
• One glucose molecule breaks down into two pyruvate molecules.
• Net gain: 2 ATP and 2 NADH per glucose molecule.

2. Krebs Cycle

• Also called the citric acid cycle or TCA cycle.
• Occurs in the mitochondrial matrix in eukaryotic cells.
• Releases carbon dioxide and produces energy carriers.

3. Electron Transport Chain (ETC)

• Occurs in the inner mitochondrial membrane.
• Produces most of the ATP during aerobic respiration.
• Oxygen acts as the final electron acceptor.

5. Human Respiratory System

The human respiratory system helps in taking oxygen into the body and removing carbon dioxide.

• Nose: Filters, warms and moistens air.
• Pharynx: Common passage for food and air.
• Larynx: Voice box.
• Trachea: Windpipe.
• Bronchi: Two main branches of the trachea.
• Bronchioles: Smaller branches of bronchi.
• Alveoli: Main site of gaseous exchange.
• Lungs: Main respiratory organs.
• Diaphragm: Major muscle involved in breathing.

6. Mechanism of Breathing

Inhalation (Inspiration)

• Diaphragm contracts and moves downward.
• Ribs move upward and outward.
• Chest cavity volume increases.
• Air enters the lungs.

Exhalation (Expiration)

• Diaphragm relaxes and moves upward.
• Ribs move downward and inward.
• Chest cavity volume decreases.
• Air moves out of the lungs.

7. Important Facts About Respiration

Topic	Answer
Energy currency	ATP
Site of glycolysis	Cytoplasm
Site of Krebs cycle	Mitochondrial matrix
Site of ETC	Inner mitochondrial membrane
Powerhouse of cell	Mitochondria
Voice box	Larynx
Windpipe	Trachea
Air sacs	Alveoli
Respiratory pigment	Haemoglobin
Major breathing muscle	Diaphragm

8. Respiration in Plants

• Plants perform respiration both day and night.
• Oxygen enters through stomata, lenticels and root surfaces.
• Exchange of gases mainly occurs by diffusion.
• Mitochondria are the main sites of aerobic respiration.

9. Difference Between Breathing and Respiration

Breathing	Respiration
Physical process	Biochemical process
Occurs through respiratory organs	Occurs in cells
Involves exchange of gases	Involves release of energy
Does not directly produce ATP	Produces ATP

10. Important One-Liners for Competitive Exams

1. Respiration releases energy from food.
2. ATP stands for Adenosine Triphosphate.
3. Mitochondria are called the powerhouse of the cell.
4. Glycolysis occurs in the cytoplasm.
5. Krebs cycle is also called the citric acid cycle.
6. Alveoli are the functional units for gaseous exchange in lungs.
7. Haemoglobin transports oxygen in blood.
8. Anaerobic respiration in yeast produces alcohol.
9. Lactic acid may accumulate in muscles during intense exercise.
10. Diaphragm is the major muscle involved in breathing.
11. Normal adult resting respiratory rate is approximately 12–20 breaths per minute.
12. Oxygen is the final electron acceptor in aerobic respiration.

EXAM TIP: Remember these three locations:
Glycolysis – Cytoplasm
Krebs Cycle – Mitochondrial Matrix
ETC – Inner Mitochondrial Membrane.

Prepare for Competitive Examinations

Study regularly, revise important Biology concepts and practise MCQs to improve your examination performance.

By Laxmidhar Sir
Laxmidhar Sir Official

Biology NotesRespirationOTETCTETOSSTETB.Ed