digestion

• metabolism is?


  the sum of all of the chemical reactions in a living organism
• Digestion


  Is an important process that helps us break down large insoluble molecules by breaking the bonds in between the individual molecules. When the bond are broken yo are left with small soluble molecules. This is done by adding water, this is hydrolysis
• carbohydrates made up of …CHO

  carbon hydrogen oxygen
• lipids are made of …

  carbon hydrogen oxygen
• nucleic acids are made of

  carbon hydrogen oxygen nitrogen
• starch is 


  storage in plants
• glycogen is 


  storage in animals
• pepsin, a protease


  works in the stomach

  optimum pH = 2
• amylase


  Works in the mouth + small intestine

  optimum pH = 7.5
• carbohydrate digested in


  mouth, small intestine
• lipids source


  milk, cheese
• saturated vs unsaturated 


  saturated get from milk / cheese

  unsaturated get from sunflower seeds +peanuts
• lipids uses

  energy stores because they are insoluble in water, they provide insulation, steroid hormones
• lipids digested 


  in small intestine
• proteins sources


  meat, fish, eggs
• protein uses 


  enzymes, transport molecules (haemoglobin), structured materials, hormones (insulin), defence against disease
• protein digested in 


  stomach, small intestine
• …% of our body i is water

  70
• 2/3 of the water is inside

  cytoplasms of cells
• 1/3 is in

  tissue fluid and blood plasma
• humans lose around … L of water by

  1.5L, by crying, sweating, breathing, urinating, throwing up
• if we lose 5% of our water we 


  fall unconscious
• if we lose 10% of our water it is


  fatal
• we replace water by

  drinking
• dietary fiber is indigestible providing


  Bulk to your faeces, its main component is cellulose
• cellulose comes from 


  skin of fruit
• fibre in our diet

  stretches the muscular walls of our gut and helps push food along by peristalsis
• consequence of low dietary fibre is

  constipation
• peristalsis happens along the tubes of the gut, not just in the oesophagus
• the stomach churns its contents mixing the food into a creamy liquid called chyme. food enter the first part of the small intestine called the duodenum
• the liquid chyme that contains partly digested food is moved onto the small intestine where digestion is completed
• amylase


  converts starch into maltose
• maltose


  a type of sugar
• the process of getting glucose from starch is 2 steps: convert starch to maltose by amylase then break it down into glucose
• trypsin (a protease) converts proteins into amino acids
• as the chyme is coming from the stomach the pH is acidic so <7. the pancreas will secrete hydrogencarbonate to neutralise the acid from the stomach
• bile


  bile is made in the liver but stored in the gall bladder.

  bile emulsifies fats. Large lipid droplets into smaller ones.

  this increases the surface area for the lipase to work on.

  bile also contains hydrogencarbonate, to neutralise the stomach acid.
• large intestine


  digestive juices are largely made of water, this is one of the major requirement of water in the body.digestive juices are largely made of water, this is one of the major requirement of water in the body.

  apart from being a solvent for biochemical reactions it is also needed for hydrolysis.

  the juices contain mucus which protecct the gut wall from being digested
• there are some substances in food we cannot digest, this is usually from plant material such as the cellulose in cell walls. this makes up dietary fibre
• water is absorbed from the chyme in the large intestine and the indigestible food is expelled, this is egestion