B6: Human nutrition

  1. Diet

  • Balanced diet: all of the food groups in the correct proportions

  • Vitamins:

    • Vitamin C:

      • foods that contain it: citrus fruits, raw vegetables

      • why its needed: make collagen, repair tissues

      • deficiency disease: scruvy → causes pain in joints and muscles and bleeding from gums and other places

    • vitamin D

      • butter, egg yolk, sunlight

      • helps calcium absorb for making bones and teeth

      • rickets → bones become soft and deformed

  • Minerals:

    • Calcium: for bones and teeth, for blood clotting.

      • found in: dairy products

    • iron: making haemoglobin

      • found in: liver, red meat,..

  1. Digestive system:

  • Alimentary canal:

    • mouth

    • oesophagus

    • stomach

    • small intestine (duodenum and ileum)

    • large intestine (colon, rectum, anus)

  • Associated organs:

    • salivary glands

    • pancrease

    • gall bladder

  • function: digest food and absorb nutrients

    • ingestion: food/drinks are taken in by the mouth

    • mechanical digestion: food is broken down without chemical change

    • chemical digestion: large insoluble molecules → small soluble molecules

    • absorption: small food molecules and ions move through the wall of the intestine into the blood

    • assimilation: nutrients get absorbed by individual cells and used for energy/make new substances

    • egestion: food that has not been digested/absorbed passes out of the body as feces

  • Digestive system functions:

    • mouth: food is ingested → mechanical digestion

    • salivary glands: secretes saliva into the mouth → lubricates food for swallowing

    • oesophagus: connects mouth to stomach

    • stomach: churns to continue the process of mechanical digestion

      • hydrochloric acid provides suitable pH for enzymes and destroys pathogens in food

    • liver: produces bile → aids digestion of fags and neutrlizes stomach acid as it exits

    • gall bladder: amylase, protease, lipase production

    • small intestine:

      • duodenum: complete chemical digestion

      • iluem: absorbtion of nutrients into the blood via villi

    • large intestine:

      • colon: formation of feces

      • rectum: storage of feces

      • anus: egestion → feces leaves the body

  1. Digestion

  • Physical:

    • breakdown of food into smaller pieces without chemical change

    • increases surface area for enzymes to react

    • carried out:

      • by chewing

      • churning of the stomach

      • emulsification of fats by bile in duodendum

  • Bile in the gallbladder:

    • alkaline to neutralize hydrochloric acid

    • breaks down large drops of fat into smaller ones (emulsification)

  • chemical digestion:

    • after physical digestion: large molecules are broken apart into smaller molecules

    • involves chemical reactions catalysed by enzymes

    • are soluble in water → easier to be absorbed into cells

  • Enzymes in digestion

    • Amylases: produced in the mouth and pancreas (secreted into duodenum)

      • starch → smaller sugars

    • Proteases: secreted in the pancreas → acts in the stomach/duodenum

      • proteins → amino acids

    • Lipases: produced in the pancreas, secreted into the duodenum

      • lipids → fatty acids and glycerol

  • Hydrochloric acid

    • Kills bacteria

    • gives acid pH for enzymes to work

    • helps stomach remain within optimum range for pepsin to work