human nutrition

• a balanced diet is a diet which contains all the essential nutrients in the right amounts
• the six essential nutrients are: carbohydrates, proteins, lipids, water, minerals and vitamins, and fibre
• increase in fat consumption results in increased fat in the bloodstream, which increases the risk of heart disease
• lack of vitamin C causes scurvy
• lack of vitamin D and calcium causes rickets
• lack of iron causes anemia
• children need more energy as they as growing
• adults need decreasing amounts of energy as they age
• ingestion is the taking in of food through the mouth
• physical digestion is the breaking down of large food pieces into smaller food pieces without a chemical change
• chemical digestion is breaking down large insoluble food molecules into smaller soluble food molecules using enzymes
• absorption is the passing of digested food molecules into the blood through the walls of the small intestine
• assimilation is the movement of digested food molecules into the cells of the body where they are used becoming part of the cell
• egestion is the removal of undigested food through the anus
• incisor: chisel shape for cutting and biting. humans have four at the front of the mouth
• canine: pointed for holding and tearing food
• pre-molar: larger surface, grinds and chews soft food, has two cusps and one or two roots
• molar: largest teeth with flat surfaces to crush hard foods, three or more cusps and multiple roots
• saliva contains amylase, sodium hydrogen carbonate and mucus
• food is moved down the oesophagus by peristalsis
• gastric juice is made up of HCl and the enzyme pepsin
• mechanical digestion happens in the mouth, stomach and small intestine
• pancreatic juice contains amylase, lipase and protease
• bile emulsifies fats and neutralises chyme (physical and chemical)
• the small intestine is made up of the duodenum and the illeum
• the small intestine's job is to break down and digest food into the blood
• the large intestine reabsorbs water from remaining material
• function of the small intestine is to digest and absorb digested food molecules into the blood
• digested food molecules are absorbed through the walls of the small intestine
• adaptations of small intetsine

  1. very long
  2. folded
  3. covered in millions of villi
• adaptations of villi

  1. wall is one cell thick
  2. covered in microvilli
  3. has a lacteal to absorb fatty acids and glycerol
  4. has capillaries to absorb glucose and amino acids
• once glucose and amino acids are absorbed into the blood they are taken by the hepatic portal vein to the liver where the glucose is converted to glycogen and stored
• deamination is the removal of the toxic amine group in the amino acid and the formation of urea from it
• deamination happens in the liver
• the crown is the visible part of the tooth
• the root is the part of the tooth hidden under the gum
• the cement holds the tooth to the gum
• the enamel is a hard, white, calcium salt
• the dentine is living tissue just below the enamel
• the pulp contains the nerves and blood vessels