digestive system sec 2

Front

carbohydrates

Back

• - provide a primary source of energy for activities, such as growth and movement

Front

fats

Back

• - provide twice the amount of energy compared to carbohydrates of the same mass

• - stored under the skin to insulate the body from exceesive heat loss

Front

proteins

Back

• - for the growth of new cells and tissues

• - repair of damaged tissues

• - sources of energy when carbohydrates and fats are not available

Front

digestion

Back

• - break down large and complex undigested food substances into small and simple digested food substances

• - when food is digested by enzymes, they become small and soluble and can pass through the intestinal walls, which is then absorbed into the bloodstream and transported to all parts of the body

Front

breaking down of different classes of food into simpler substances

Back

carbohydrates -> maltose -> glucose

fats -> glycerol and fatty acids

proteins ->polypeptides -> amino acids

Front

physical digestion

Back

• - physical breakdown of large pieces of food into smaller pieces

• - chemical properties of food substances remain unchanged, so no new products are formed

• purpose : to increase the surface area

• where it occurs : mouth - chewing action

• stomach- churning action

Front

chemical

Back

• - it is a process where by large and complex food substance are chemically broken down to form small and simple new substances

• purpose : to allow food substances to enter the bloodstream through the intestinal wall

• where it occurs : mouth and oesophagus - starch

• stomach - proteins

• small intestine - carbohydrates, fats and proteins

Front

enzymes

Back

carbohydrases -> speed up breakdown of carbohydrates into simple sugars

proteases -> they speed up the breakdown of proteins into amino acids

lipases -> they speed up the breakdown of fats into fatty acids and glycerol

Front

human digestive system

Back

made of : mouth, oesophagus, stomach, small instestine, large intestine, rectum and anus

*not part of digestive system :

Front

mouth

Back

physical digestion - the teeth chew food to cut and grind it into smaller pieces

chemical digestion - carbohydrases partially digest starch

saliva contains salivary amylase ( a type of carbohydtase) that digests starch into maltose

• - no proteins or fats are digested