Edexcel A Level (IAL) Biology -7.1 Overview of Respiration- Study Notes- New Syllabus

Aerobic Respiration

🌱 Introduction

Aerobic respiration is the process by which cells release energy from organic molecules (like glucose) in the presence of oxygen. It provides energy for all cellular activities and is more efficient than anaerobic respiration.

1. Overall Reaction

Organic molecules (respiratory substrates, e.g., glucose) are split. Hydrogen atoms are reunited with oxygen. Carbon is released as carbon dioxide (CO₂). Large amounts of energy are released and stored in ATP molecules.

General equation:
\[ \text{Glucose} + O_2 \rightarrow CO_2 + H_2O + \text{Energy (ATP)} \]

Key points:

• CO₂ is a waste product.
• Oxygen is the final hydrogen acceptor.
• Energy is captured in ATP molecules.

2. Respiration as a Stepped Process

Aerobic respiration does not release all energy at once. It occurs in a series of small, controlled steps, allowing energy to be harvested efficiently. Each step is catalysed by a specific intracellular enzyme. Stepwise release prevents energy loss as heat and allows ATP production.

🟢 Key Points

• Glucose is gradually broken down → CO₂ + H₂O + energy.
• Hydrogen from glucose is passed to oxygen to form water.
• Each step is enzyme-controlled → prevents uncontrolled reactions.
• Occurs in all aerobic cells, mainly in mitochondria.

📋 Summary Table