BB 6 - Enzymes Flashcards
(26 cards)
What are enzymes?
Highly specific globular proteins that are biological catalysts produced by living things.
What do enzymes do?
Speed up chemical reactions in cells and organisms
What is the main purpose of enzymes?
Allow reactions to be regulated and controlled
How is an enzyme-substrate complex formed?
When a substrate binds to the active site of the enzyme.
What happens to the enzyme after the substrate binds?
The enzyme changes shape slightly to fit the substrate more exactly (induced-fit model).
What is the induced-fit model?
Occurs after a substrate molecule binds to the active site of the enzyme, where the enzyme slightly changes shape to fit the substrate more exactly.
How do enzymes increase reaction rate?
- Lower activation energy of a biological reaction.
- Bring substrate molecules together in correct orientation for a reaction to occur (induced-fit model).
- Put stress on chemical bonds of the substrate molecule, causing the bonds to break and reform with less energy input.
What factors can influence enzyme activity?
Temperature pH Inhibitors (Competitive and Non-competitive) Reactant Concentration Enzyme Concentration
How does temperature affect enzyme activity?
Different enzymes work at different optimal temperatures.
What happens when the enzyme is at optimal temperature?
The enzyme maintains its shape and has greatest number of successful collisions with substrate molecules.
What happens when the temperature of a reaction is too low?
The kinetic energy in the enzyme and substrate molecules is low, which causes less successful collisions to occur.
What increases as temperature increases?
Kinetic energy
What happens when the temperature of a reaction is too high?
The protein denatures (loses tertiary shape and converts back to secondary or primary structure.
How do proteins denature when the temperature is too high?
The high amount of energy (heat) overcomes the secondary bonding (hydrogen bonding) between the amino acids.
What happens when an enzyme loses its tertiary shape?
Can no longer recognise and bind to its substrate due to loss of specificity, slowing down reaction rate.
What happens when the pH is lower or higher than the optimum?
The enzyme denatures causing it lose its shape, slowing down reaction rate.
How many types of inhibitors are there?
Two
What are the two types of inhibitors?
Competitive
Non-competitive
How do competitive inhibitors affect enzyme activity?
Have similar shape to the substrate molecule which competes to bind to the active site of the enzyme.
How can the effect of competitive inhibitors be overcome?
Increasing the substrate concentration to increase chances of substrate binding to the active site of the enzyme instead of the inhibitor.
How do non-competitive inhibitors affect enzyme activity?
Have a different shape to the substrate molecule, which binds to the allosteric site instead of the active site.
When the inhibitor binds, the shape of the enzyme becomes distorted, causing the active site to be no longer complementary to the substrate molecule.
They do not compete with substrate molecules for binding.
How can the effect of non-competitive inhibitors be overcome?
The effect cannot be overcome by increasing substrate concentration.
How does reactant / substrate concentration affect enzyme activity?
Increases the rate of a biological reaction.
When is the maximum reaction rate achieved?
When all the enzyme’s active sites are occupied by substrate molecules
