Chapter 4: Enzymes Flashcards
What are enzymes made of?
Globular proteins.
Why do enzymes have hydrophilic R groups on their surface?
To ensure they are soluble in water.
What is the active site of an enzyme?
The region where the substrate binds.
What does the induced fit hypothesis describe?
Enzymes and substrates change shape slightly to ensure a perfect fit.
What happens to enzymes after catalyzing a reaction?
They remain unchanged.
What is a substrate?
The molecule that binds to the enzyme’s active site.
What is an enzyme-substrate complex?
The temporary structure formed when a substrate binds to an enzyme.
How do enzymes lower activation energy?
By holding substrates in a position that facilitates reaction.
What happens to the bacterial cell wall when lysozyme acts on it?
It loses rigidity and the cell bursts.
What type of reaction does lysozyme catalyze?
Hydrolysis.
What determines an enzyme’s specificity?
The shape of its active site.
What is activation energy?
Energy required to start a chemical reaction.
What is the effect of low temperature on enzymes?
Slower movement of molecules
=> Smaller KE
=> Less collisionsions with active site
=> Slower reaction rates.
What happens to enzymes above their optimal temperature?
They denature
=> Loses functions.
What does denaturation mean?
Loss of enzyme shape and function.
How does pH affect enzymes?
Alters the ionic bonds
=> Change 3D structure of enzymes.
What happens to enzymes at extreme pH levels?
They denature.
How does substrate concentration affect reaction rate initially?
The rate increases with substrate concentration.
Molecules more chance to interact with active site
What happens when enzymes are saturated with substrate?
The reaction rate plateaus.
Why does the reaction rates plateau when substrate concentration increase indefinitely?
Enzymes reached max rate, all enzymes are linked to molecules
=> Add more won’t help
What is competitive inhibition?
An inhibitor competes with the substrate for the active site.
What are competitive inhibitors?
Molecules with similar shape to enzyme’s substrate.
Can competitive inhibition be reversed?
Yes, by increasing substrate concentration to compete again.
Can competitive inhibition stop all reactions?
Competitive inhibitors can’t compete with all, substrate can still bind to active site.
What is non-competitive inhibition?
An inhibitor binds to an allosteric site
Can non-competitive inhibition be reversed by increasing substrate?
No
What is the allosteric site?
A site on the enzyme other than the active site.
What is end-product inhibition?
When the end product of a reaction inhibits the enzyme’s activity.
Why is end-product inhibition beneficial?
It prevents overproduction and waste of resources.
What is the role of enzymes in metabolism?
To catalyze reactions.
What happens when inhibitors bind to the active site?
They block substrate binding.
How does an allosteric inhibitor affect the active site?
It distorts the site, making it forever insuitable for substrates
=> irreversible
What happens in a hydrolysis reaction?
A molecule is broken down by water.
What prevents substrate binding in competitive inhibition?
The inhibitor occupies the active site.
What type of inhibition does not depend on substrate concentration?
Non-competitive inhibition.
What is negative feedback in enzyme activity?
Regulation where the product inhibits the process.
What happens to reaction rates when enzymes are at their optimum?
They are at their peak.
Why does adding substrate not always increase reaction rates?
Enzymes have a saturation point.
Why are enzymes reusable?
They are unchanged after the reaction.
How is the reaction rate related to enzyme concentration?
Higher enzyme concentration increases the rate
What happens when an inhibitor binds to the allosteric site?
It causes a conformational change in the enzyme.
How does the cell control enzyme activity in metabolic pathways?
Through feedback mechanisms like end-product inhibition.
What makes non-competitive inhibition irreversible in some cases?
Strong binding of the inhibitor to the enzyme.
How does the induced fit model benefit enzyme efficiency?
It enhances the binding between enzyme and substrate.
What happens to the enzyme once the product is released?
It is free to catalyze another reaction.
What is the lock-key hypothesis?
Active sites are fixed and specific
=> 1 type of enzyme binds to 1 type of substrate.
