Biology-Term 1 '24

• Nutrition: The process of obtaining the energy and nutrients needed for growth and development.
• The function of food: To provide energy, to provide building materials for growth and repair, to provide regulating substances like vitamins and minerals. Helps the body stay healthy.
• Proteins are located in all meat, dairy and legumes.
• All enzymes are proteins.
• All anti-bodies are proteins
• Lack of proteins in your diet can lead to: retarded physical and mental growth, decreased resistance to diseases, Kwashiorkor, Marasmus/Starvation.
• Carbohydrates are located in all the grain products, bread, rice, potatoes and sugar products.
• Carbohydrates act as the most important fuel/source of enery
• Respiration uses glucose to supply cells with ATP
• Lack of carbohydrates in the diet can lead to Marasmus
• Fats/Lipids are located in oils, butter, cheese, milks, eggs, nuts, fish and meat.
• Fats act as the body's reserve energy source/fuel
• Fats insulate the body against heat loss
• Fats act as packaging material and shock absorbers in between organs
• Functions of water:

  • It is a medium for chemical reactions
  • It acts as a lubricant that allows the food to move smoother
  • It acts as a solvent that helps nutrients get absorbed
  • It acts as a reagent during hydrolysis
  • It acts as a transport medium for the absorbed nutrients seeing as water is a large component of the blood (2/3 water) and the blood transports all absorbed nutrients.
• Lack of water in the diet include: Dehydration and death
• Functions of minerals and vitamins: They act as regulatory substances in the body for growth and health.
• Lack of vitamins and minerals in the diet include:

  • Anaemia
  • Rickets
  • Goitre
  • Scurvy
  • Night blindness
• Fibre: Includes roughage in the diet mainly consisting of cellulose.
• Sources of fibre include any whole grain products, fruits and vegetables
• The functions of fibre include:

  • It promotes peristalsis
  • It promotes constipation
  • It prevents colon cancer
• Peristalsis is moving food in your body.
• Lack of fibre in the diet include:

  • Constipation, because too little water remains in the food, therefore it slows down peristalsis and it becomes difficult to egest/ defecate.
  • Too much fibre in the diet can cause diarrhoea, because too much water remains in the food and therefore it speeds up peristalsis.
• Ingestion: The intake of food.
• Digestion: The break down of large, complex, insoluble molecules into smaller, more soluble and absorbable molecules.
• Absorption: The movement of small nutrients from the digestive tract into the blood.
• Assimilation: The incorporation of absorbed nutrients into the body tissues e.g. amino acids are used to build muscle.
• Defecation/Egestion: The removal of all the undigested, unabsorbed food remains (faeces) by the colon.
• Oral Cavity/Mouth, teeth and tongue: The teeth chew the food and breaks it into smaller pieces through mechanical digestion. These smaller pieces can be digested faster and absorbed more easily.
• The tongue is a muscle, it performs the following functions:

  1. It is a taste organ
  2. It mixes the food with the saliva
  3. It pushes the food between the teeth so that it can be chewed
  4. It rolls the food into a bolus
  5. It aids the swallowing action by pressing onto the upper hard palate and forcing the bolus into the pharynx (throat)
• Salivary glands secrete saliva.
• Saliva is a slightly alkaline substance that contains the enzyme salivary amylase that breaks down cooked starch to maltose.
• Saliva consists mainly of water, but also contains mucous that helps to bind the food and the lubricate it can be more easily swallowed.
• The oesophagus stretches from the pharynx/throat to the stomach.
• Food is pushed forward through peristalsis until it reaches the stomach.
• The epiglottis closes the opening to the airways/trachea (the glottis) during the swallowing process to prevent choking.
• Peristalsis refers to the rhythmical contractions of the intestinal muscles to push the food forward.
• Stomach is the only part of the digestive tract that contains an acid medium.
• The stomach juice contains hydrochloric acid (HCL) and enzymes that digest proteins especially.
• The stomach:

  1. It is antiseptic
  2. It breaks down some sugars
  3. It creates the correct pH for enzymes to function in the stomach.
  4. It is also lined with a mucous membrane that protects it against the functioning of the enzymes and hydrochloric acid.
  5. When food enters the stomach strong churning movements start to mix the food with the stomach juice and break it down.
  6. Food that leaves the stomach is called chyme.