Digestive System-Enzymes Flashcards
Describe the role of enzymes in digestion
Enzymes are required for most of the chemical reactions that occur in organisms. These reactions occur in the breakdown of chemical molecules in the digestive system.
Describe how enzyme activity is affected by
temperature and pH changes.
Higher temperatures disrupt the shape of the active site, which will reduce its activity, or prevent it from working. The enzyme will have been denatured. Enzymes are also sensitive to pH. Changing the pH of its surroundings will also change the shape of the active site of an enzyme.
Explain enzyme action using the ‘lock and key
theory
The substrate – the molecule or molecules taking part in the chemical reaction – fits into the active site. Once bound to the active site, the chemical reaction takes place. In an organism, the active site of each enzyme is a different shape. One enzyme is therefore specific to one substrate’s chemical reaction, or type of chemical reaction.
Recall the sites of production and the reactants and products of
amylase, proteases and lipases.
Amylase breaks down starch into glucose. It is produced in the pancreas and salivary glands.
Proteases break down proteins into amino acids. It is produced in the small intestine and stomach and pancreas.
Lipases break down lipids into fatty acids and glycerol. It is produced in the pancreas.
Describe a method to investigate the effect of pH
on the rate of reaction of amylase enzyme
1) Place single drops of iodine solution on dimple tile
2) Label a test tube with the pH to be tested
3) Use the syringe to place 2cm3 of amylase in the test tube
4) Add 1cm3 of buffer solution to the test tube using a syringe
5)Use another test tube to add 2cm3 of starch solution to the
amylase and buffer solution, start the stopwatch whilst mixing
using a pipette
6) After 10 seconds, use a pipette to place one drop of the mixture
on the first drop of iodine
7) Wait another 10 seconds and place another drop of the mixture
on the second drop of iodine
8) Repeat every 10 seconds until iodine solution remains orange-
brown
9) Repeat experiment at different pH values
Explain what the products of digestion are used for
in the body.
Carbohydrate is turned into glucose, which our bodies need to make energy.
Protein is turned into amino acids, required for cell growth and repair.
Lipids are turned into fatty acids and glycerol, needed to insulate our bodies and make cell membranes.
Give the sites of production and storage of bile
Is produced in the liver, but stored and concentrated in the gall bladder.
Describe the function of bile and explain why it is
alkaline
Contains sodium hydrogencarbonate, which is an alkali. It neutralises stomach acid and produces the optimum pH for pancreatic enzymes.
