F212 Enzymes

Question 0

What’s an organic cofactor (coenzyme)?

Answer 0

They’re organic molecules that participate in the reaction and are changed by it (like a second substrate). They normally act as carriers and move chemical groups between different enzymes and are continually recycled during the process.

Question 1

What’s an inorganic cofactor?

Answer 1

A non protein substance that works by helping the enzyme and substrate to bind together without directly participating in the reaction so they’re not changed.

Question 2

Describe competitive inhibition.

Answer 2

The inhibitor molecules have a similar shape to the substrate molecules. They compete with the substrate to bind to the active site but no reaction takes place. Instead, they block the active site. How much the enzyme is inhibited depends on the concentration of the inhibitors and substrates. This is reversible inhibition.

Question 4

Describe non-competitive inhibition.

Answer 4

Non competitive inhibitor molecules bind to the enzyme away from it’s active site which causes the active site to change shape so the substrate can no longer bind to it. This is non-reversible.

Question 5

How do you determine whether inhibition is reversible or non-reversible?

Answer 5

• Inhibition will be reversible if the bonds between the active site and the substrate are weaker hydrogen bonds or weak ionic bonds so the inhibitor can be removed. (E.G. COMPETITIVE INHIBITION)
• Inhibition will be non-reversible if the bonds between the substrate and the active site are strong covalent bonds as the inhibitor cant be removed easily and will be irreversible.

Question 6

What’s a metabolic poison?

Answer 6

A substance that interferes with metabolic reactions (reactions that occur in cells) and can cause damage, illness or even death.

Question 7

Describe the action of one named metabolic poison.

Answer 7

Cyanide is a non-competitive inhibitor of cytochrome c oxidase (an enzyme that catalyses respiration reactions). Cells that cant respire die.

Question 8

Enzyme action can be intracellular - what does this mean?

Answer 8

Occur within cells.

Question 9

Enzyme action can be extracellular - what does this mean?

Answer 9

Occur outside of cells.

Question 10

What are enzymes?

Answer 10

Globular proteins with a specific tertiary structure which catalyse metabolic reactions in living organisms.

Question 11

What’s the active site?

Answer 11

A place on the enzyme where the substrate binds to.

Question 12

Talk about specificity.

Answer 12

The substrate and the active site need to be complementary to each other in order to bind.

Question 13

What’s the enzyme substrate complex?

Answer 13

The molecule formed after the substrate binds to the active site on the enzyme.

Question 14

How does enzymes lower activation energy?

Answer 14

Enzymes reduce the energy needed to start the reaction by usually making reactions happen at a lower temperature which speeds up the rate of reaction.

Question 15

What’s the enzyme product complex?

Answer 15

The substrate forms into two products whilst bounded to the active site.

Question 16

Whats the lock and key hypothesis?

Answer 16

The substrate fits into the enzyme in the same way that the key fits into the lock - the active site and substrate have a complementary shape.

Question 17

Whats the induced fit model?

Answer 17

It builds on the lock and key hypothesis. The substrate and active site need to have complementary shapes but the substrate also needs to change the active site in the right way as well.