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Biochemistry > Enzymes > Flashcards

Enzymes Flashcards

1
Q

What do proteases do?

A

Degrade proteins

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2
Q

What do phosphatases do?

A

Remove phosphates

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3
Q

What do ribonucleases do?

A

Cleave RNA molecules

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4
Q

How doe enzymes work?

A

They lower the activation energy required for the molecular reaction to take place.

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5
Q

What are co-factors?

A

Non-protein molecules which assist in the biochemical transformation

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6
Q

What are the two classes of co-factors?

A
  • Coenzymes
  • Prosthetic groups
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7
Q

What are the differences between the two classes of co-factors?

A
  • Coenzymes are loosely bound
  • Prosthetic groups are tightly bound
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8
Q

What do prosthetic groups do?

A

They act as activators and/or inhibitors of activity.

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9
Q

What do coenzymes do?

A
  • They catalyse reactions.
  • Transfer electrons
  • Form/break a covalent bond
  • Transfer a group
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10
Q

What are examples of coenzymes?

A
  • NAD+ / NADH
  • Coenzyme A
  • Vitamins
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11
Q

What are examples of prosthetic groups?

A

They are small inorganic ions.
- Mg
- Mn
- Fe
- Zn
- Cu

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12
Q

When are enzymes most stable?

A

In a transition state

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13
Q

How does temperature affect enzymes?

A
  • Temperature causes the rate of interactions to go up; therefore the rate of catalysis goes up
  • However, higher temperatures cause denaturation of the enzyme - The shape changes; therefore loses its activity
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14
Q

How does the substrate concentration affect enzyme activity?

A
  • Increasing the concentration of substrate increases the rate of reaction fairly linear, the enzyme is processing the substrate quicker than the substrate can find the enzyme
  • The rate of reaction stops increasing at a certain point as the enzyme is full when the substrate meets it because there’s so much substrate there, the collisions is now faster than the enzyme can process the substrate
  • At this point adding more substrate will not change anything as the enzyme is already full.
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15
Q

In terms of Michaelis-Menten kinetics, what does V mean?

A

Mols of product per second (the rate of the catalytic reaction)

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16
Q

In terms of Michaelis-Menten kinetics, what does Vmax mean

A

The maximum observed rate

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17
Q

What happens at high substrate concentrations [S] in terms of V and S?

A

V is nearly independent of S

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18
Q

In terms of Michaelis-Menten kinetics, what does S mean?

A

Substrate concentration

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19
Q

In terms of Michaelis-Menten kinetics, what does ES mean?

A

Enzyme substrate

20
Q

In terms of Michaelis-Menten kinetics, what does EP mean?

A

Enzyme product

21
Q

What is the Michaelis-Menten equation for an enzyme product?

A

E + S –> ES –> Ep
E + S –> ES is reversible

22
Q

In terms of Michaelis-Menten kinetics, how do you determine the rate of formation of EP?

[ES]

A

V = K3[ES]

23
Q

In terms of Michaelis-Menten kinetics, how do you determine the rate of formation of ES?

[E][S]

A

V = K1[E][S]

24
Q

In terms of Michaelis-Menten kinetics, how do you determine the rate of breakdown of EP?

A

V = (K2+K3)[ES]

25
Q

What is the Michaelis equation when under steady conditions [ES] is constant whilst substrate and product may vary?

[E][S]=[ES]

A
  • Rate of breakdown = Rate of formation
  • K1 [E][S] = (K2+K3)[ES]
26
Q

How do you calculate Km?

A

(K2+K3)/K1
Units is mol dm3

27
Q

What is the Michaelis-Menten equation involving Km?

A

[ES] = ([E] [S]) / Km

28
Q

In terms of Michaelis-Menten kinetics, what does ET stand for?

A

Total enzyme

29
Q

What is the Michaelis-Menten equation involving ET?

A

[ES] = [ET] x [S] / ([S] + Km)

30
Q

What is the main Michaelis-Menten equation?

A

V = Vmax x [S] / ([S] + Km)

31
Q

If [S] &laquo_space;Km then…

A

Rate is proportional to [S]
V = Vmax ([S] / Km)

32
Q

If S = Km then…

A

Rate is half Vmax
V = Vmax ([S] / ([S] +[S])) =Vmax / 2

33
Q

If [S]&raquo_space; Km then…

A

Rate is Vmax
V = Vmax [S] /[S] = Vmax

34
Q

In terms of Michaelis Menten what is K2?

A

K2 is going from ES back to E + S

35
Q

In terms of Michaelis Menten what is K3?

A

k3 is going from Es –> EP

36
Q

How do enzymes lower activation energy?

A
  • An enzyme molecule must interact specifically with the substrate molecule or a small number of closely related substrates
  • The molecule (or substrate) fits within a particular cavity on the enzyme (active site) and is attracted to particular points of charge within the cavity
37
Q

Binding substrate

A

E + S <-> ES

38
Q

Substrate converted to bound product

A

ES <-> EP

39
Q

Release of product

A

E + P

40
Q

What is activation energy?

A

Barrier to spontaneous reaction

41
Q

What stabilises the transition state complex?

A

Diverse interactions

42
Q

At a low concentration of substrate…

A
  • The catalytic site of the enzyme is empty, waiting for the substrate to bind.
  • The rate at which product can be formed in limited by the concentration of substrate available.
43
Q

Competitive inhibition

A

Inhibition competes reversibly with substrate for active site

44
Q

Uncompetitve inhibition

A

Inhibitor binds only to the Es complex leading to EIS intermediates. This is very rare

45
Q

Non-competive inhibition

Allosteric

A

Inhibitor binds non-covalently to sites other tan the active site.
Partially inhibited enzymes can still turn over substrate

46
Q

Irreversible inhibition

A

Irreversible inhibitors form covalent or very tight bonds with functional groups in active site.

Biochemistry (18 decks)

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