Enzymes Flashcards
Define an enzyme and its structure.
An enzyme is a biological catalyst - speeding up the rate of reaction without being changed or used up in the process.
It is made up of long chains of amino acids that are folded into unique shapes.
Describe the ‘Lock and Key’ model of enzyme action.
The shape of the substrate is complementary to the shape of the active site of the enzyme.
So, enzymes can only catalyse specific reactions.
When they bond, this forms an enzyme-substrate complex.
Once bonded, the reaction takes place and the products are released, but the enzyme remains unchanged.
How does temperature affect enzyme activity?
At first, an increase in temperature increases the rate of reaction - to an optimum (around 37 degrees celsius).
This is due to more collisions between enzymes and substrates as they are moving faster.
Once the temperature becomes too hot, the bonds holding the enzyme together begin to break, which changes the shape of the active site.
So, the enzyme will not be able to bind to the substrate and becomes denatured.
How does pH affect enzyme activity?
Enzymes have an optimum pH where the activity is at maximum.
If the pH becomes too acidic / alkaline, the shape of the active site is changed.
So, the enzyme becomes denatured.
Describe a method to investigate the effect of pH on amylase activity.
- Put a drop of iodine solution into each well of a spotting tile.
- Using a syringe, add 2cm^3 of amylase solution to one test tube, 2cm^3 of starch solution to another test tube and 2cm^3 of a pH 5 buffer solution to a final test tube.
- Place all 3 test tubes in a water bath at 35 degrees celsius, and wait 10 minutes for the solutions to reach the correct temperature.
- Combine all 3 solutions into one test tube and mix with a stirring rod, then immediately return the test tube to the water bath.
- Start a stopwatch, after 30 seconds add a drop of the solution into a well.
- Use continuous sampling every 30 seconds, until the solution turns from blue-black to brown-orange.
- Record the time it took for the solution to turn browny-orange - when starch is no longer present.
- Repeat the experiment with different pH buffer solutions.
What is the formula to calculate rate of reaction, and what are the units?
Rate = 1000/time
Units are s^-1
What is the function of digestive enzymes?
Digestive enzymes break down large, insoluble molecules into smaller, more soluble molecules.
What is the function of proteases?
Proteases break down proteins into amino acids.
There are found in : the stomach, pancreas and small intestine.
What is the function of carbohydrases?
Carbohydrases break down carbohydrates into simple sugars.
Eg.)
Starch consists of a long chain of glucose molecules.
Starch is broken down by amylase to produce maltose.
What is the function of carbohydrases, and where are they produced?
Carbohydrases break down carbohydrates into simple sugars.
Eg.)
Starch consists of a long chain of glucose molecules.
Starch is broken down by amylase to produce maltose.
Amylase is found in : the salivary glands, pancreas and small intestine.
What is the function of lipases, and where are they produced?
Lipases break down lipids to produce glycerol and fatty acids.
Lipids consist of one glycerol molecule attached to three molecules of fatty acid.
Lipase is found in : the pancreas and the small intestine.
Describe and explain the role of bile in digestion.
Bile is produced in the liver, stored in the gall bladder and then released into the small intestine.
Bile emulsifies lipids by breaking them down into smaller droplets, increasing their surface area so that lipase can work faster.
Bile is alkaline to neutralise the acidic conditions in the stomach, creating alkaline conditions in the small intestine.
So, this increases the rate of lipid digestion by lipase.
