Digestion Flashcards
Describe what happens in the digestive system
- Starch (a carb), proteins and fats are insoluble.
- They are broken down into soluble substances by enzymes, so that they can be absorbed in the blood stream in the wall of the small intestine
- in the large intestine excess water is absorbed from the food into the bloodstream
- the indigestible food that remains makes up faeces which leaves the body via the anus
All the parts of the digestive system
How are enzymes important to the digestive system
Enzymes help break down food
- they are large proteins that act as biological catalysts. They increase the rate of chemical reactions and used in the digestive system to break down insoluble molecules into soluble ones to be absorbed in the bloodstream
Features of enzymes
- the shape of an enzyme is vital for the enzymes function, as this decide what substance it can bind to
High temperatures denature enzymes by breaking the bond holding it together , changing the shape of their active sight so they can no long bind to their substrate - different enzymes work best at different pH levels
If it’s too high or low the pH will interfere with the bonds holding the enzyme together
This changes the shape of the active site, denaturing the enzyme
All enzymes have an optimum pH they work best at
Investigating how different pH and temperatures affect enzyme activity
Required practical
1) put a drop of iodine solution into every well of a spotting tile
2) place a tripod and gauze over a Bunsen burner, put a beaker of water on top of the tripod and heat till 35C
All the digestive enzymes
Amylase:
Produced in the salivary glands, pancreas and small intestine
- breaks down starch into glucose in the mouth and small intestine
Protease:
produced by the stomach, pancreas and small intestine
- breaks down proteins into amino acids in the stomach and small intestine
Lipase:
Produced by the pancreas and small intestine
- breaks down lipids into 3 strings of fatty acids and glycerol in the small intestine
What is the job of the stomach
1) pummels foods with its muscular walls
2) produces protease, pepsin
3) produces hcl to kill bacteria and keep the optimum pH for the protease enzyme to work
What is the job of the liver
- produces bile, which is stored in the gallbladder before being released into the small intestine
- bile neutralises the hcl mixed with the food from the stomach, this provides optimum alkaline conditions in which the enzymes in the small intestine can work best in + bile emulsifies fats, this increases the surface area of the fats for lipase enzymes to act on
How do proteins become denatured
- the long chains of amino acids that make up proteins are folded, coiled and twisted to make specific 3d shapes
- it is these shapes that allow allow other molecules to fit into the protein
- the bonds that hold the proteins in these shapes are sensitive to temperature and pH and can easily be broken, lesson to the enzyme becoming denatured
Functions of proteins
- act as hormones
- act as enzymes
- act as antibodies
- act as structural components of tissues
What is the job of the small intestine
- digested food molecules are absorbed from the small intestine to the blood stream to reach cells, this is done by a combination of diffusion and active transport
Diffusion:
digested food molecules are able to diffuse from the small intestine to the blood vessels as there is a very high conc of food molecules in the gut and a much lower conc in the blood. So the food moves down a conc gradient
- the lining of the small intestine is folded into thousands of little projections called villi. These increase the surface area of the gut lining, allowing more food molecules to diffuse at a time
- the lining of the small intestine also has great blood supply, maintaining a steep conc gradient for diffusion
- the lining is one cell thick, decreasing diffusion distance
Active transport:
- as the time from your last meal increases, there will be more food molecules in the blood than the gut, so active transport is used to move the food molecules against a conc gradient
What is the job of the gall bladder
- stores bile and releases it into the small intestine when needed
What are all the food tests
Carbohydrates-
* iodine test for starch
(Yellow red to blue black)
* hot Benedict’s solution for glucose
(Blue to brick red)
Proteins-
* biuret test for proteins
(Blue to purple)
Lipids-
* ethanol test for lipids
(Gives cloudy white layer)
What is the job of the large intestine
- where water is absorbed from the undigested food into the bloodstream
- this leaves feces which are excreted out of the anus
