Catalysts and Enzymes

This final section focuses on the role of catalysts and enzymes in biological processes, a crucial topic for GCSE Biology B3 revision notes.

Key points include:

1. Enzymes are biological catalysts that speed up chemical reactions without being consumed in the process.
2. The rate of chemical reactions in living organisms is controlled by enzymes.
3. Enzymes have specific 3D shapes that allow other molecules to fit into them, enabling their catalytic function.
4. The bonds that hold proteins (including enzymes) together are sensitive to temperature and pH changes.
5. If these bonds are broken, the enzyme's shape may be lost, potentially rendering it non-functional – a process called denaturation.

Definition: Denaturation occurs when an enzyme's structure is altered due to changes in temperature or pH, often resulting in a loss of function.

Understanding the nature and function of enzymes is essential for answering AQA GCSE Biology digestive system exam questions and comprehending the broader concepts of biological organisation.

This section ties together the previous information on food chemistry and digestion, providing a comprehensive overview of how the body processes nutrients at a molecular level.

The Human Digestive System

This section delves into the structure and function of the human digestive system, a key topic in GCSE Biology organisation revision notes. The digestive system breaks down large, insoluble food molecules into smaller, soluble molecules that can be absorbed and utilized by cells.

The main components of the digestive system include:

1. Mouth: Physically breaks down food
2. Salivary glands: Produce saliva containing enzymes
3. Oesophagus: Transports food to the stomach
4. Liver: Releases bile into the small intestine to aid fat digestion
5. Stomach: Churns food with acids and enzymes
6. Pancreas: Produces digestive enzymes
7. Small intestine: Absorbs small, soluble molecules into the bloodstream
8. Large intestine: Main site of water absorption
9. Rectum: Stores feces before excretion
10. Anus: Muscular ring for feces excretion

Highlight: The small intestine is crucial for nutrient absorption and uses muscular tissue to physically push material along the digestive tract.

The text also introduces the main digestive enzymes:

1. Amylase: Breaks down carbohydrates into simple sugars
2. Protease: Breaks down proteins into amino acids
3. Lipase: Breaks down lipids into glycerol and fatty acids

Vocabulary: Bile is not an enzyme but plays a vital role in digestion by increasing pH for lipase to work effectively and emulsifying lipids to increase surface area for enzyme action.

This comprehensive overview of the digestive system is essential for answering B3 organisation and the digestive system exam-style questions.