Enzymes and factors affecting enzyme activity Flashcards
What do enzymes do?
They are large proteins that speed up reactions inside living things by acting as catalysts.
What are catalysts?
A catalyst is a substance which increases the speed of a reaction, without being changed or used up in the reaction.
Describe the ‘lock and key’ model.
Every enzyme has an active site with a unique shape.
The substrate involved in the reaction has to fit into the active site for the enzyme to work. (Enzyme/substrate complex formed).
The enzyme changes shape slightly as the substrate binds.
Enzyme/product complex.
Substrate is broken down, releasing two products.
What factors affect enzyme activity?
Temperature and pH.
How does temperature affect enzyme activity?
Affects the rate of reaction, a higher temperature increases the rate - but an enzyme denatures if it gets too hot so the substrate can’t fit anymore.
What is meant by denaturing?
When the shape of the active site changes as a result of bonds within the enzyme breaking.
What is the optimum temperature?
The temperature that enzymes work best at - around 37 degrees.
How does pH affect enzyme activity?
Affects the rate of reaction - if the pH is too high or too low, it affects the bonds holding the enzyme together and so the enzyme denatures.
What is meant by optimum pH?
The pH that enzymes work best at - optimum pH depends where the enzyme works.
How do you calculate the rate of reaction?
rate = 1000 / time
What do amylase do?
An example of carbohydrases.
Made in the salivary glands, pancreas and small intestine,
Works in the mouth and small intestine.
Breaks down starch into sugars.
What do proteases do?
Made in the stomach, pancreas and small intestine.
They work in the mouth and small intestine.
Breaks down proteins into amino acids.
What do lipases do?
Made in the pancreas and small intestine.
Work in the small intestine.
Breaks down lipids (fats and oils) into glycerol and fatty acids.
What do digestive enzymes do?
They break down big molecules (starch, proteins and fats) into smaller, soluble molecules so that they can be absorbed into the bloodstream.
What are the products of digestion used for?
To build new carbohydrates, lipids and proteins - some glucose is used for respiration.
