Enzymes

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What is an enzyme?
A biological catalyst which increases the speed of a reaction without being changed or used up in the reaction
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What is a substrate?
A molecule that is changed in a reaction
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What is an active site?
The part where a substrate joins on to an enzyme - specific to a substrate
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What affect can changing the temperature have on an enzyme?
Below optimum temperature, it will increase the rate of reaction, as the particles will have more energy, giving a higher collision rate. Above optimum temperature, bonds holding the active site together will break down - the enzyme will be denatured
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What is pepsin and what its optimum pH?
It is an enzyme used to break down proteins in the stomach and its optimum pH is 2
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Describe the experiment to investigate the effect of temperature on enzyme activity, by measure of the rate at which the product is produced
Put hydrogen peroxide in a test tube with a source of catalase (potato). Put test tube in water bath. Connect to delivery tube and measure how fast oxygen is produced. Repeat with water bath at different temperatures
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Describe the experiment to investigate the effect of temperature on enzyme activity, by measure of the rate at which the substrate disappears
Put starch solution and amylase enzyme in test tube in water bath. Drop mixture every minute onto iodine on spotting tile. If starch is present, the iodine solution will turn from browny-orange to blue-black.
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How do you know when the starch has been broken down?
The iodine solution will stay browny-orange
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What does amylase do?
It breaks down starch into maltose
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What does maltase do?
It breaks down maltose into glucose
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What does protease do?
It breaks down proteins into amino acids
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What does lipase do?
It breaks down lipids into glycerol and fatty acids
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What is the purpose of bile?
It is alkaline, so it neutralises the hydrochloric acid from the stomach to allow enzymes in the small intestine to work best. Also emulsifies fats into tiny droplets, giving them a bigger surface area for lipase to work on, making digestion faster
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Where is bile produced and stored?
It is produced in the liver, stored in the gall bladder and released into the small intestine
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What enzyme do the salivary glands produce?
Amylase
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What are the functions of the stomach?
To pummel food with its muscular walls, produce the protease enzyme, pepsin, and produce hydrochloric acid in order to kill bacteria and give the right pH for pepsin (pH 2)
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What is the oesophagus?
A muscular tube that connects the mouth and the stomach
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What enzymes does the pancreas produce?
Protease, amylase and lipase to release into the small intestine
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What is the function of the small intestine?
To produce lipase, amylase and protease enzymes to complete digestion, and to absorb nutrients out of the alimentary canal and into the body
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What is the function of the large intestine?
This is where excess water is absorbed from food
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Describe peristalisis
The contraction of circular muscles along the alimentary canal that squeeze boluses through the gut
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What is ingestion?
Putting food or drink in your mouth
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What is digestion?
The break-down of large insoluble molecules into small soluble molecules by mechanical methods (teeth and stomach muscles) and chemical methods (enzymes and bile)
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What is absorption?
The process of moving molecules through the walls of the intestine into the blood. Digested food molecules are absorbed in the small intestine, and water is mainly absorbed in the large intestine
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What is assimilation?
When digested molecules are moved into body cells and become part of the cells, e.g. when amino acids are assimilated they are used to make cellular proteins
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What is egestion?
The process of undigested matter exiting the body in the form of faeces
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How is the small intestine adapted for absorption of food?
It's very long, allowing more time to absorb all food. It has a very big surface area, due to millions of villi, which in turn have microvilli, a single permeable layer of surface cells and a good blood supply
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Card 2

Front

What is a substrate?

Back

A molecule that is changed in a reaction

Card 3

Front

What is an active site?

Back

Preview of the front of card 3

Card 4

Front

What affect can changing the temperature have on an enzyme?

Back

Preview of the front of card 4

Card 5

Front

What is pepsin and what its optimum pH?

Back

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