cofactors + enzyme inhibition Flashcards
(22 cards)
What is a cofactor? (2)
A non-protein compound required for an enzyme’s activity;
There are three types: coenzymes, activators, and prosthetic groups
What are coenzymes? (3)
Organic cofactors that do not bind permanently;
They participate in the reaction and are changed by it, acting as carriers of chemical groups between enzymes;
Most coenzymes are derived from vitamins (e.g., NAD from niacin, which acts as a hydrogen acceptor)
What are activators? (4)
Inorganic metal ions;
That temporarily bind to the enzyme and alter its active site;
Making the reaction more feasible;
They do not directly participate in the reaction and are not used up
What are prosthetic groups? (3)
Cofactors that are permanently attached to the enzyme;
Example: Zn²⁺ is a prosthetic group for carbonic anhydrase;
Which catalyses the production of carbonic acid from water and carbon dioxide in red blood cells
What is an inhibitor? (2)
A substance that slows down or stops a reaction;
By affecting the binding of the substrate to the enzyme
How do competitive inhibitors work? (2)
They have a similar structure to the substrate and bind to the enzyme’s active site;
Competing with the substrate and decreasing the enzyme’s activity
How does substrate concentration affect competitive inhibition? (1)
Increasing substrate concentration reverses the effect by outcompeting the inhibitor
How does competitive inhibition affect product formation? (1)
The amount of product remains the same, but the rate of product formation decreases
How do non-competitive inhibitors work? (2)
They bind to a site away from the active site (allosteric site);
Changing the shape of the active site and preventing substrate binding
How does substrate concentration affect non-competitive inhibition? (1)
Increasing substrate concentration has no effect on non competitive inhibition
What are reversible inhibitors? (3)
Bind to enzyme’s active site through hydrogen bonds or weak ionic interactions;
So they do not bind permanently;
They can be competitive or non-competitive
What are irreversible inhibitors? (2)
Form strong covalent bonds with the enzyme;
Permanently affecting its activity
What are some examples of irreversible inhibitors? (2)
Cyanide;
Heavy metal ions like mercury and silver
How do reverse transcriptase inhibitors work? (2)
Inhibit the enzyme reverse transcriptase;
Preventing viral replication by stopping viral DNA replication
How does penicillin work as an enzyme inhibitor? (3)
Inhibits transpeptidase;
Which weakens bacterial cell walls;
Causing the bacterial cell to burst and die
How does cyanide affect metabolic reactions? (2)
Irreversible inhibitor of cytochrome oxidase;
Preventing respiration and causing cell death
What metabolic enzymes do malonate and arsenic inhibit? (2)
Malonate inhibits succinate dehydrogenase;
Arsenic inhibits pyruvate dehydrogenase, both of which catalyse respiration reactions
What is product inhibition? (1)
Occurs when an enzyme is inhibited by the product of the reaction it catalyses
What is end-product inhibition? (2)
Occurs when the final product in a metabolic pathway inhibits an enzyme earlier in the pathway;
Regulating the pathway and controlling the amount of product made
Are product and end-product inhibition reversible? (2)
Yes;
When the level of product drops, the level of inhibition decreases, allowing the enzyme to function again
Why are some enzymes synthesised as inactive precursors? (2)
To prevent them causing damage to cells e.g. proteases;
Which could damage proteins in the cells where they are made
How do inactive precursors become active? (2)
Part of the precursor molecule inhibits the enzyme;
Once this part is removed, the enzyme becomes active
