Chapter 8 delves into human nutrition, beginning with the principal sources and dietary importance of essential nutrients. From carbohydrates and lipids to vitamins and mineral salts, each nutrient plays a critical role in supporting bodily functions and maintaining overall health. Understanding the sources and potential deficiencies of these nutrients is crucial for promoting a balanced and healthy diet.
Principal Sources and Dietary Importance:
- Carbohydrates:
- Sources: Grains, fruits, vegetables.
- Importance: Main energy source; provides fuel for bodily functions.
- Lipids:
- Sources: Oils, nuts, avocados.
- Importance: Energy storage, cell membrane structure; source of essential fatty acids.
- Proteins:
- Sources: Meat, beans, dairy.
- Importance: Building blocks for tissues, enzymes, hormones; essential for growth and repair.
- Vitamins (C and D):
- Sources: C – Citrus fruits, D – Sunlight, fortified foods.
- Importance: C – Antioxidant, collagen synthesis; D – Bone health, calcium absorption.
- Mineral Salts (Calcium and Iron):
- Sources: Calcium – Dairy, leafy greens; Iron – Meat, legumes.
- Importance: Calcium – Bone and teeth formation; Iron – Oxygen transport in blood.
- Fibre (Roughage):
- Sources: Whole grains, fruits, vegetables.
- Importance: Aids digestion, prevents constipation.
- Water:
- Sources: Beverages, fruits, vegetables.
- Importance: Essential for hydration, digestion, and various physiological functions.
Diseases and Symptoms from Deficiencies:
- Vitamin C Deficiency (Scurvy):
- Symptoms: Fatigue, swollen and bleeding gums, joint pain.
- Vitamin D Deficiency (Rickets):
- Symptoms: Soft and deformed bones, delayed growth in children.
- Calcium Deficiency (Osteoporosis in Adults, Rickets in Children):
- Symptoms: Brittle bones, skeletal deformities.
- Iron Deficiency (Anaemia):
- Symptoms: Fatigue, pale skin, weakness.
Balanced Diet Concept:
- Definition: A diet that provides all essential nutrients in appropriate proportions.
- Importance: Supports optimal growth, development, and maintenance of health; prevents nutritional deficiencies or excesses.
Understanding the sources, importance, and potential deficiencies of essential nutrients helps in promoting a balanced and healthy diet for overall well-being.
GCSE Biology – What are Nutrients? Carbohydrates, Lipids, Proteins, Vitamins & Minerals #15
Human Digestive System
1. Main Regions of the Digestive System:
- Mouth, Salivary Glands, Oesophagus, Stomach, Small Intestine (Duodenum and Ileum), Pancreas, Liver, Gallbladder, Large Intestine (Colon, Rectum, and Anus).
2. Need for Digestion:
- Explanation: Most foods must be digested to break down complex molecules into simpler ones for absorption.
- Importance: Allows nutrients to be absorbed and utilised by the body.
3. Physical Digestion:
- Definition: Breakdown of food into smaller pieces without changing the chemical structure of food molecules.
4. Chemical Digestion:
- Definition: Breakdown of large molecules into small molecules through enzymatic action.
5. Relationship Between Physical and Chemical Digestion:
- Surface Area Increase: Physical digestion increases the surface area of food, facilitating enzyme action in chemical digestion.
6. Types of Human Teeth:
- Incisors, Canines, Premolars, Molars.
7. Structure of Human Teeth:
- Components: Enamel, Dentine, Pulp, Nerves, Cement.
- Embedding: Teeth are embedded in the gum.
8. Functions of Types of Human Teeth in Physical Digestion:
- Incisors: Cutting and biting.
- Canines: Tearing and shredding.
- Premolars and Molars: Crushing and grinding.
9. Functions of Main Regions of the Digestive System
- Mouth:
- Ingestion, physical digestion, chemical digestion of starch by amylase.
- Salivary Glands:
- Secretion of saliva containing amylase.
- Stomach:
- Physical digestion, chemical digestion of protein by protease, presence of hydrochloric acid in gastric secretions.
- Small Intestine (Duodenum and Ileum):
- Chemical digestion of starch by amylase, maltose by maltase, protein by protease, and lipids by lipase.
- Liver:
- Production of bile and storage of glycogen.
- Gallbladder:
- Storage of bile.
- Pancreas:
- Alkaline secretion containing amylase, protease, and lipase.
- Ileum and Colon:
- Absorption.
- Rectum and Anus:
- Egestion.
Functions of Enzymes
- Amylase: Breaks down starch to maltose.
- Maltase: Breaks down maltose to glucose.
- Protease (Pepsin and Trypsin): Breaks down protein to amino acids.
- Lipase: Breaks down lipids to fatty acids and glycerol.
Role of Hydrochloric Acid in the Stomach:
- Function: Kills ingested bacteria.
pH Levels and Proteases:
- Explanation: Different proteases in the stomach and duodenum work optimally at different pH levels.
Role of Bile:
- Function: Emulsifies fats, increasing the surface area for lipase action in the chemical digestion of fats to fatty acids and glycerol.
Peristalsis:
- Definition: Waves of contractions of longitudinal and circular muscles moving food through the digestive system.
Understanding the structure, functions, and processes of the human digestive system is crucial for comprehending the breakdown and absorption of nutrients for maintaining overall health.
GCSE Biology – Digestive System #18
Absorption and Assimilation:
1. Small Intestine as the Region of Nutrient Absorption:
- Statement: The small intestine is the primary region where nutrients are absorbed.
2. Absorption Mechanisms:
- Understanding: Nutrients move from the intestines into cells lining the digestive system and then into the blood.
- Mechanisms: Includes diffusion, osmosis, and active transport.
3. Assimilation:
- Definition: The uptake and use by cells of nutrients from the blood.
4. Villus Structure and Roles:
- Structure: Finger-like projections in the small intestine.
- Roles:
- Capillaries: Absorb nutrients (e.g., glucose, amino acids) into the blood.
- Lacteals: Absorb lipids (fats) into the lymphatic system.
5. Significance of Villi and Microvilli:
- Internal Surface Area Increase:
- Villi and microvilli significantly increase the internal surface area of the ileum.
- Enhances nutrient absorption efficiency.
6. Water Absorption:
- Understanding: Water is absorbed from the lumen of the small intestine and the colon.
- Significant Absorption: Most water absorption occurs in the small intestine.
7. Function of Hepatic Portal Vein:
- Statement: The hepatic portal vein serves as the route taken to the liver by most molecules and ions absorbed from the ileum.
- Role: Allows the liver to process and regulate absorbed nutrients before they enter the general circulation.
Understanding the processes of absorption and assimilation, along with the structural adaptations in the small intestine, is crucial for comprehending how nutrients are acquired and utilised by the body.
Small intestine and food absorption | Physiology | Biology | FuseSchool
Exploring the human digestive system reveals a complex network of organs and processes dedicated to breaking down and absorbing nutrients. From the mouth to the small intestine, each region performs specific functions, such as physical and chemical digestion, absorption, and assimilation. Understanding these processes and structural adaptations enhances our comprehension of how nutrients are acquired and utilized by the body, essential for maintaining optimal health and well-being.
