| Question | Answer |
| digestion | the breaking down of the nutrients in food, so that they can be absorbed into the bloodstream from the alimentary canal. |
| aim of digestion | to break down the large insoluble molecules in food into small soluble molecules so you can absorb them into your blood plasma or lymph. |
| mechanical/physical digestion | the breakdown of large particles of food into small ones, by teeth and the churning movements produced by muscles. allows food to pass easily through the digestive system and provides larger surface area for chemical digestion. |
| chemical digestion | the large molecules (that are too big to pass through the cell membranes) after physical digestion broken down into small ones with the help of enzymes so they can pass through cell membranes. involves chemical changes from one sort of molecule 2 another |
| enzymes | biological catalysts that speed up reactions without being used up. proteins made by living organisms. |
| 3 main types of digestive enzyme | carbohydrase (inluding amylase, maltase), protease, lipase |
| enzyme to break down starch | amylase |
| enzyme to break down maltose | maltase |
| enzyme to break down protein | protease |
| enzyme to break down fats (lipids) | lipase |
| breaking down of starch | starch -> amylase -> maltose -> maltase -> glucose |
| breaking down of proteins | proteins -> protease -> amino acids |
| breaking down of lipids (fats) | lipids -> lipase -> glycerol + fatty acids |
| substrate | a substance on which enzymes act |
| active site | part of enzyme molecule in which substrate binds.1 enzyme will only accept 1 substrate. |
| why are enzymes highly specific? | The active site has to be the right shape for the substrate molecules to fit into. This means that enzymes have a high specificity for their substrate – a particular type of enzyme will only work with one or a smaller number of substrates. |
| properties of enzymes | enzymes are proteins, catalysts, are made inactive at high temperatures, work best at a particular pH (optimum pH), work best at a particular temp (optimum temp) |
| what happens as temperatures increase to enzymes? | speeds up rate of reaction until optimum temperature is passed when it denatures (lose shape, structure, function) |
| what happens at low temperatures to enzymes? | stops working, doesn't denature |
| what happens at extreme high/low pH to enzymes? | denature |
| pepsin optimum pH | low (stomach acid) |
| enzyme at small intestine optimum pH | high |
| most enzyme optimum pH | 7 |
| optimum temperature for most enzymes | body temperature |
| where is protease active | stomach |
| where is lipase active | small intestine |
| oseophagus | oesophagus connects mouth to stomach, carries food from mouth to stomach |
| stomach | (stomach) protein digestion starts in strongly acidic conditions, where the enzyme pepsin works best |
| stomach | (stomach) HCl acid released here kills germs |
| Liver | (liver) bile salts made by liver which also breaks down many waste products in blood |
| Gall bladder | (gall bladder in liver) stores biles until they are secreted to small intestine via bile duct |
| Duodenum | (duodenum - 1st 30cm of small intestine) has many small glands in its walls which produce enzymes such as maltase and peptidase |
| Pancreas | (pancreas) produces several enzymes including amylase, lipase and peptidase enzymes. they are released through the pancreatic duct into the duodenum |
| Duodenum | enzyme lipase breaks down fats which have already been split into tiny drops by bile salts, occurs her/ |
| Small Intestine | small soluble molecules pass through into blood stream. fold on inner surface called villi provide a larger surface area for absorption. |
| Large intestine | water passes from gut to blood stream |
| Rectum | only a small proportion of the faeces is made up of indigestible remains of food. faeces are mostly intestinal secretions, dead cells and an enormous amount of bacteria. faeces are stored in the rectum. |
| Anus | faeces are egested (removed from body) in anus |
| monosaccharide | a simple sugar; a sugar whose molecules are made up of a single sugar unit (e.g. glucose, fructose) |
| disaccharide | a sugar made of molecules which consist of 2 monosaccharide units joined together with no intermediates (e.g. maltose, sucrose) |
| polysaccharide | a carbohydrate such as starch or cellulose, whose molecules are made of many sugar units joined together (not sweet, e.g. starch) |
| food types for balanced diet | carbohydrates/starch, sugar, mineral salts, vitamins, water, fibre, protein, fat |
| food types associated with energy | starch, sugar, fat |
| health | fibre, water, vitamins, mineral salts, protein |
| growth | protein |
| foods which contain fat | butter, cake, milk, chocolate, chips |
| foods which contain protein | fish, eggs, chicken, milk, cheese |
| foods which contain simple sugars | fruit, chocolate, sweets |
| foods which contain starch | potatoes, rice, bread |
| food test: STARCH. solution, original colour, is heat needed, final colour if the result is positive | iodine, orange, no, blue-black |
| food test: SIMPLE SUGARS. solution, original colour, is heat needed, final colour if the result is positive | Benedict's solution, blue, yes, green -low, yellow -med, red -high. |
| food test: FAT. solution, original colour, is heat needed, final colour if the result is positive | pure ethanol, clear, no, milky emulsion |
| food test: PROTEIN. solution, original colour, is heat needed, final colour if the result is positive | Biuret's (KOH CuSO4), blue, no, purple/violet (the > the protein, the richer the colour) |
| bile salts | enzymes in the small intestine work best in alkaline conditions but food is acidic after stomach. Bile is alkaline substance. it emulsifies fats in small intestine - important, because it provides a larger surface area in which the lipases can work. |
| Chief cell | Site of production of pepsinogen |
| Parietal cells | site of production of HCL |
