nutrition

• Carbohydrates are essential for maintaining normal brain function and providing energy.
• monosaccharide: glucose, fructose, galactose
• disaccharide: sucrose, maltose, lactose
• polysaccharide: starch, cellulose, glycogen
• glucose + glucose = maltose
• glucose + fructose = sucrose
• glucose + galactose = lactose
• carbohydrates provides energy
• basic unit of protein is amino acids
• basic unit of carbohydrate is glucose
• basic unit of fat is fatty acids & glycerol
• protein formation: amino acids -> peptides -> polypeptides -> protein
• 20 types of protein: 9 essential, 11 non-essential
• function of protein: growth, build new tissues, repair damaged cells, replace dead cells
• 2 types of fats: saturated fats & unsaturated fats (healthier)
• functions of fats: insulation, provide energy, protect organs
• enzymes are highly specific
• enzymes can be reused
• enzymes can be affected by: temperature, pH value, concentration of enzyme, concentration of substrate
• digestion: process by which the body breaks down food into smaller substances
• 2 types of digestion: mechanical digestion & chemical digestion
• mechanical digestion: mastication & peristalsis
• chemical digestion: action of enzymes & hydrolysis
• salivary glands secretes salivary amylase to digest starch into maltose in the mouth
• stomach secretes pepsin to digest protein into polypeptides and rennin to digest caseinogen into casein
• pancreas secretes pancreatic amylase to digest starch into maltose in the stomach, trypsin to digest polypeptides into peptides and lipase to digest fat into fatty acid and glycerol
• small intestine secretes erepsin to digest peptide into amino acid, lactase to digest lactose into glucose+galactose, sucrase to digest sucrose into glucose+fructose and maltase to digest maltose into glucose+glucose
• alimentary canal: mouth>oesophagus>stomach>small intestine>large intestine>rectum>anus
• digestive glands: salivary glands, gastric glands, liver, pancreatic glands, intestinal glands
• mouth: beginning of digestion, mucus moistens the food and the tongue shapes it into a bolus
• oesophagus: the bolus is pushed into the stomach by the contraction and relaxation of the walls of the oesophagus, this process is called peristalsis
• stomach: food mixes with gastric juices which contains hydrochloric acid, pepsin, rennin and mucus (secreted by gastric glands)

  hydrochloric acid provides an acidic medium for enzyme action, kills bacteria in food and activates enzymes

  mucus protects stomach wall
• duodenum is the first part of the small intestine and is connected to the liver and pancreas

  bile and pancreatic juice flow to the duodenum during digestion

  bile is a greenish juice produced by the liver and stored in the gall bladder, its main function is to emulsify fat into tiny droplets and increase surface area for action of lipase

  pancreatic juice contains pancreatic amylase, trypsin and lipase
• small intestine secretes intestinal juices which contain erepsin, lactase, sucrase, maltase and water
• absorption of nutrients takes place in the small intestine by diffusion
• water soluble end products: glucose & amino acids enter the blood circulatory system by diffusion and is transported to the liver via hepatic portal vein
• fat soluble end products: fatty acids, glycerol and vitamin A,D,E,K are absorbed by lacteals and carried to the vein by the lymphatic system