Enzymes Flashcards Preview

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Flashcards in Enzymes Deck (25):
1

what do Oxidoreductases do ?

Transfer electrons

2

What type of enzyme forms isomers (transfers groups within a molecule) ?

Isomerase

3

What type of enzyme enables hydrolysis ?

Hydrolase

4

What type of enzyme forms double bonds & adds groups to double bonds ?

Lyase

5

What does Isomerase do ?

Forms isomers (transfers groups within a molecules)

6

What do ligases do ?

Forms bonds via ATP splitting

7

What type of enzyme forms bonds via ATP splitting ?

Ligases

8

What type of enzyme transfers electrons ?

Oxidoreductase

9

What is desolvation

Where an enzyme loses hydrogen bonds

10

What is induced fit ?

Where a protein changes shape to induce a lock & key formation & a conformational change takes place when the substrate binds

11

Define ∆H

Enthalpy change: Change in potential energy (∆H must be negative for a reaction to take place)

12

Define ∆S

Entropy change: Change in disorder, the more disordered the more likely the reaction.

13

Name 3 ways enzymes lower the activation energy ?

Decrease entropy: Particles more aligned and less energy is required to collide.
Desolvation: Where weak H bonds between enzyme & substrate are replaced by strong H bonds between substrate and aqueous soloution
Induced fit: conformational changes in enzyme allow enzyme and substrate to bind.

14

What is happening at V0 ?

The reaction is at a steady state (initial reaction velocity) & ES is stable

15

What is Vmax & what does it tell us about the reaction ?

Vmax is the maximum reaction velocity where the enzyme is saturated with substrate. Vmax tells us how fast the reaction is.

16

What is Km & how is it calculated ?

Km is Michaelis constant & is calculated as half of Vmax.

17

What does Km tell us about the reaction ?

High Km = Loose fit and unstable
Low Km = Tight fit and stable
Stability of ES complex

18

What is a non-competitive inhibitor ?

It binds to the enzyme but not at the active site.

19

What does a non-competitive inhibitor do to the Vmax and the Km ?

Vmax: Is decreased due to the binding & possible change of active site, reaction slowed.
Km: Unchanged as substrate can still bind to active site.

20

What is a competitive inhibitor ?

It binds to the active site on the enzyme

21

What does a competitive inhibitor do to the Vmax and the Km ?

Vmax: Unchanged as enzyme can overcome inhibition by increasing substrate inhibition.
Km: Increased, as the inhibitor does not fit the enzyme as tight as the substrate therefore high Km means loose fit and unstable.

22

What are the properties of Allosterically-regulated enzymes ?

Made up of many sub-units with many biding sites
Cooperatively bound
They are examples of non-competitive inhibitors
Bind to the enzyme and change the shape of binding site

23

What is a concerted model enzyme ?

Where binding to one active site opens up all active sites and allows S to bind more effectively

24

What is a sequential model enzyme ?

Where S binding to an active site only opens one active site a ta time in sequence.

25

What is a covalently-modified enzyme ?

They are reversible and have multiple phosphorylation sites allowing for fine tuning of enzyme function.