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Flashcards in Enzymes 2 Deck (18)
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1
Q

Define isozymes.

A

Different proteins which catalyse the same reactions i.e glucokinase and hexokinase.

2
Q

What reaction do glucokinase and hexokinase catalyse?

A

Glucose + ATP -> Glucose-6-Phosphate +ADP + Pi

3
Q

What does a high Km mean?

A

Low affinity for substrate and a slower reaction. (Glucokinase).

4
Q

What does a low Km mean?

A

High affinity for substrate and a faster reaction. (Hexokinase).

5
Q

What can it mean if enzymes are found in the wrong place?

A

It means there is cell damage and there may be a leakage of enzymes into the bloodstream.

6
Q

Define ternary complex.

A

An enzyme with 2 or more substrates bonded to it.

7
Q

Do allosteric enzymes follow M-M kinetics?

A

No

8
Q

Allosteric enzymes are…

A

Made up of many subunits which contain many active sites.

9
Q

What 3 things will affect an enzyme?

A
Increased temperature (increase molecule collisions, increase molecule energy but will eventually denature)
pH (changes charges of amino acids, extremes can denature, affects substrates which may need a hydrogen or hydroxide ion group)
Inhibitors
10
Q

Define a competitive inhibitor.

A

Mimics the substrate. Binds to the active site stopping the substrate from being able to bind.

Bind non-covalently. Decrease affinity between active site and substrate so Km increases.

11
Q

Define an uncompetitive inhibitor.

A

Bind near the active site and block the product leaving the active site.

12
Q

Define a noncompetitive inhibitor.

A

Binds at another point of the protein, altering the active site.

Bind non-covalently. Substrate can usually bind to active so Km remains constant but an increase in substrate concentration will do nothing so Vmax decreases.

13
Q

Define transition state analogues.

A

Inhibitor mimics the transition state instead of the substrate. Hard to isolate as they are an intermediate step.

14
Q

Define catalytic antibodies.

A

Can be generated against potentially any biological molecule and therefore are made specifically for transition state molecules.

15
Q

What makes an irreversible inhibitor irreversible?

A

Bind covalently.

16
Q

Define allosteric effectors.

A

Usually cell metabolites that bind non-covalently to a site on an enzyme which isn’t the active site.

17
Q

Define concerted model.

A

Each subunit can exist in 2 different conformations and all subunits must be in the same conformation.

18
Q

Define sequential model.

A

No flipping between different conformations but binding causes conformational changes.