Summary Notes - Topic 7 Human Nutrition - CAIE Biology IGCSE

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Page 2: Nutrients and Their Importance

• Essential Nutrients: Humans need a variety of nutrients for survival, which must be consumed in appropriate quantities through a balanced diet.

  • Each individual requires different amounts of nutrients based on:

    • Age

    • Gender

    • Physical activity level

    • Special conditions: Pregnant and breastfeeding women require additional nutrients for the health of both mother and baby.

Types of Nutrients

• Carbohydrates:

  • Sources: Pasta, rice, potatoes.

  • Function: Major energy source for cellular respiration.

• Fats and Oils:

  • Sources: Fatty meats, cheese, butter.

  • Roles in organisms:

    • Energy storage

    • Insulation

    • Waterproofing

    • Structural components

    • Protection of organs.

• Proteins:

  • Sources: Meat, fish, eggs.

  • Function: Broken down into amino acids during digestion. Amino acids are crucial for:

    • Protein synthesis (enzymes, structural components).

    • Hormonal signaling (e.g., hemoglobin for oxygen transport).

• Vitamins:

  • Vitamin C: Found in citrus fruits and vegetables. Necessary for:

    • Protein synthesis for skin, ligaments, blood vessels.

    • Tissue repair.

  • Vitamin D: Found in dairy, eggs, fish oil. Important for:

    • Calcium absorption.

    • Bone health.

• Mineral Ions:

  • Calcium: Needed for bones and teeth, found in dairy and fish, important for blood clotting.

  • Iron: Found in red meat and green vegetables, vital for hemoglobin in blood (oxygen transport); deficiency can cause anemia and fatigue.

• Fibre (Roughage):

  • Sources: Vegetables, fruits, whole grains.

  • Function: Aids the movement of food through the digestive system, adds bulk (not digested).

• Water:

  • Sources: 80% from drinks, 20% from food.

  • Role: Solvent for chemical reactions, temperature regulation, and acts as a metabolite.

Malnutrition

• Defined as an imbalance in nutrient intake, leading to various health conditions:

  • Scurvy: Caused by vitamin C deficiency; symptoms include bleeding, stunted growth, and dry skin/hair.

  • Rickets: Caused by vitamin D deficiency; results in weak bones, deformities, and impaired growth in children.

Page 3: Continued Nutrients and Malnutrition

• Details on malnutrition:

  • Vitamin deficiencies can lead to serious health issues, emphasizing the importance of a balanced diet.

Page 4: Digestive System Overview

• Digestion: Process of breaking down food into smaller components for absorption.

  • Involves Physical Digestion and Chemical Digestion:

    • Physical Digestion: Break down of food into smaller pieces without altering chemical structure (e.g., chewing).

      • Increases surface area for enzymes.

    • Chemical Digestion: Breakdown of large, insoluble molecules into smaller, soluble ones using enzymes (absorption).

  • Absorption: Occurs primarily in the small intestine where nutrients enter the blood.

  • Egestion: Removal of undigested food as feces.

Page 5: Structure of the Digestive System

• Mouth and Salivary Glands:

  • Mechanical digestion by teeth and chemical digestion initiated by salivary enzymes (carbohydrase).

• Oesophagus:

  • Transports food from mouth to stomach via peristalsis.

• Stomach:

  • Contains protease enzymes and hydrochloric acid to digest protein and kill bacteria.

• Small Intestine (duodenum and ileum):

  • Neutralizes stomach acid; secretes necessary digestive enzymes (protease, lipase, amylase).

  • Absorption of digested food occurs here.

• Pancreas:

  • Secretes enzymes for digestion into the small intestine.

• Liver:

  • Produces bile which aids in neutralizing stomach acid and emulsifying fats.

• Gall Bladder:

  • Stores bile until needed.

• Large Intestine:

  • Passes indigestible food; absorbs water and salt.

Page 6: Digestive Processes

• Key Processes:

  • Ingestion: Taking food into the mouth.

  • Digestion: Breakdown of food into simpler molecules (both physical and chemical).

  • Absorption: Primarily in the small intestine.

  • Assimilation: Transport of nutrients to cells via bloodstream for use.

  • Egestion: Removal of waste via anus as feces.

Physical Digestion

• Mechanics:

  • Involves teeth breaking down food into smaller pieces without chemical alteration; increases efficiency of enzyme action.

Page 7: Tooth Structure and Digestion

Tooth Structure

• Enamel: Hard outer layer protecting the tooth.

• Dentine: Softer inner layer beneath enamel, susceptible to decay.

• Pulp: Contains nerves and blood vessels; central part of the tooth.

• Cement: Stabilizes roots of the tooth, covered by gums for protection.

Role of Physical Digestion in Stomach

• Stomach's muscular walls mix and grind food for further processing.

Role of Bile

• Emulsifies fats to increase surface area for digestion by lipases.

Page 8: Chemical Digestion and Enzymes

Chemical Digestion

• Breakdown of large insoluble molecules into small soluble molecules for absorption and metabolic use.

Types of Enzymes

• Amylase: Breaks down starch into maltose; found in saliva and small intestine.

  • Follow-up: Maltase converts maltose to glucose.

• Protease: Breaks down proteins into amino acids; includes pepsin (stomach) and trypsin (small intestine).

• Lipase: Breaks down fats into glycerol and fatty acids; secreted into the small intestine.

Digestion Aids

• Hydrochloric Acid: Increases acidity, crucial for protease activity and sanitizing food by killing bacteria.

• Bile: Alkaline, neutralizes stomach acid for optimal enzyme activity in the small intestine.

Page 9: Absorption of Nutrients

Absorption Mechanism

• Occurs primarily in the small intestine.

• Adaptations for Absorption:

  • Villi and microvilli increase surface area for nutrient uptake.

  • Capillaries in villi transport absorbed nutrients.

  • Maintains high concentration gradient for nourishment diffusion.

  • Lacteals absorb fats.

• Water Absorption: Primarily happens in the small intestine and in the colon.