BIO101 – Topic 25: Cellular Respiration and Energy
Production
Course Code: BIO 101 | Course Name: General Biology
© Lesuyai Organic Guides 2025 (Original | Educational | Professional | Plagiarism-Free | A4
Format)
25.1 Introduction
Every living cell requires energy to perform essential life processes such as movement, growth,
repair, and reproduction. This energy is derived from the breakdown of food molecules in a process
known as cellular respiration. Cellular respiration converts biochemical energy from nutrients into
adenosine triphosphate (ATP) — the energy currency of the cell.
25.2 Definition of Cellular Respiration
Cellular respiration is a biochemical process by which cells break down glucose and other organic
molecules to release energy in the form of ATP. It ensures that energy stored in food is made
available for biological functions.
25.3 Types of Cellular Respiration
1. **Aerobic Respiration** – Occurs in the presence of oxygen. Produces large amounts of ATP and
mainly takes place in the mitochondria. 2. **Anaerobic Respiration (Fermentation)** – Occurs in the
absence of oxygen. Produces less ATP and takes place in the cytoplasm.
25.4 Stages of Aerobic Respiration
**1. Glycolysis (in cytoplasm)** Glucose (6C) is broken down into 2 molecules of pyruvate (3C).
This process yields 2 ATP and 2 NADH. **2. Krebs Cycle (Citric Acid Cycle)** Takes place in the
mitochondria. Pyruvate is oxidized into carbon dioxide while producing NADH, FADH■, and 2 ATP.
**3. Electron Transport Chain (ETC)** Occurs on the inner mitochondrial membrane. Electrons from
NADH and FADH■ are transferred to oxygen, producing about 34 ATP and water as a byproduct.
25.5 Summary of Aerobic Respiration Equation
C■H■■O■ + 6O■ → 6CO■ + 6H■O + 38ATP Meaning: One glucose molecule combines with
oxygen to produce carbon dioxide, water, and 38 ATP molecules.
25.6 Anaerobic Respiration (Fermentation)
Production
Course Code: BIO 101 | Course Name: General Biology
© Lesuyai Organic Guides 2025 (Original | Educational | Professional | Plagiarism-Free | A4
Format)
25.1 Introduction
Every living cell requires energy to perform essential life processes such as movement, growth,
repair, and reproduction. This energy is derived from the breakdown of food molecules in a process
known as cellular respiration. Cellular respiration converts biochemical energy from nutrients into
adenosine triphosphate (ATP) — the energy currency of the cell.
25.2 Definition of Cellular Respiration
Cellular respiration is a biochemical process by which cells break down glucose and other organic
molecules to release energy in the form of ATP. It ensures that energy stored in food is made
available for biological functions.
25.3 Types of Cellular Respiration
1. **Aerobic Respiration** – Occurs in the presence of oxygen. Produces large amounts of ATP and
mainly takes place in the mitochondria. 2. **Anaerobic Respiration (Fermentation)** – Occurs in the
absence of oxygen. Produces less ATP and takes place in the cytoplasm.
25.4 Stages of Aerobic Respiration
**1. Glycolysis (in cytoplasm)** Glucose (6C) is broken down into 2 molecules of pyruvate (3C).
This process yields 2 ATP and 2 NADH. **2. Krebs Cycle (Citric Acid Cycle)** Takes place in the
mitochondria. Pyruvate is oxidized into carbon dioxide while producing NADH, FADH■, and 2 ATP.
**3. Electron Transport Chain (ETC)** Occurs on the inner mitochondrial membrane. Electrons from
NADH and FADH■ are transferred to oxygen, producing about 34 ATP and water as a byproduct.
25.5 Summary of Aerobic Respiration Equation
C■H■■O■ + 6O■ → 6CO■ + 6H■O + 38ATP Meaning: One glucose molecule combines with
oxygen to produce carbon dioxide, water, and 38 ATP molecules.
25.6 Anaerobic Respiration (Fermentation)
