Biology: Food Tests and Macronutrients

Food Tests

• Iodine Test: Used to identify starch.
• Benedict's Test: Used to detect sugars.
• Biuret Test: Used to identify proteins.
• Ethanol Test: Used to identify lipids.
• Safety Note: Biuret solution is corrosive; ethanol is flammable and harmful.

Similarities and Differences of Macronutrients

• Carbohydrates, lipids, and proteins are vital for the body's structure and function.
• They differ in their structure and functions.

Catalysts and Enzymes

• Catalysts: Substances that speed up chemical reactions without being used up.
• Enzymes: Proteins that are biological catalysts, accelerating metabolic reactions.
• Active Site: The specific region on an enzyme where the substrate binds.
• Mechanism: Enzymes decrease the activation energy, enabling reactions to proceed faster.
• Specificity: Each enzyme is tailored to a specific substrate (lock-and-key).
• Optimal Conditions: Enzymes function best at specific temperatures and pH levels.
• Denaturation: High temperatures or extreme pH can alter enzyme shape and function.
• Metabolism: Enzymes are essential in building and breaking down molecules in cells.
• Examples: Amylase (starch), lipase (fats), and protease (proteins) are examples of enzymes.

Digestive Enzymes and their Function

• Practical Experiment: Practical work involving the breakdown of hydrogen peroxide by catalase.
• Digestion: Enzymes break down food molecules into smaller absorbable units.
• Diverse Digestive Enzymes: Different digestive enzymes function in distinct sections of the digestive tract, at varying pH levels.
• Carbohydrate Digestion: Carbohydrases like amylase break down carbohydrates to sugars. Amylase originates in salivary glands and pancreas
• Protein Digestion: Proteases break down proteins into amino acids; these enzymes are found in the stomach, pancreas, and small intestine.
• Fat Digestion: Lipases break down fats into fatty acids and glycerol; these enzymes are in the pancreas and small intestine.
• Effect of pH on Amylase: The rate of amylase activity is influenced by pH; investigations involve exploring the effect of different pH levels on amylase activity.

Learning Objectives

• Understand the digestion process, role of digestive enzymes, and the breakdown of different food types.

Key Points

• Digestive enzymes are specialized cells in glands and digestive tract lining.
• They accelerate the breakdown of carbohydrates, proteins, and fats.

Synoptic Links

• Further information on moving substances across cell membranes is available in relevant chapters.

Historical Context

• Dr. William Beaumont's studies on Alexis St. Martin (stomach fistula) advanced understanding of digestion.

Digestive Enzymes: Further Details

• Enzymes accelerate food breakdown for absorption.
• Optimal Temperature: Enzymes function best at body temperature (37°C).
• pH Levels: Different enzymes operate optimally at varying pH levels.
• Stomach Acidity: Hydrochloric acid maintains a low pH in the stomach.
• Pancreatic Enzymes: These enzymes work best in alkaline conditions.
• Bile's Role: Bile emulsifies fats, increasing the surface area for lipase action.
• Gallstones: Can block bile ducts, causing pain.
• Stomach Mucus: Thick mucus coating protects the stomach lining from acid.
• Acid Attack: Stomach lining damage can occur by acid and enzymes, leading to discomfort.
• Surface Area: Increased food surface area can influence digestion efficiency.