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Biochemistry 1 BB10003 > lecture 7 - enzymes > Flashcards

lecture 7 - enzymes Flashcards

1
Q

What does the effect of pH have on the enzyme?

A

protein structural changes - affects the state of protonation within the active site

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2
Q

What effect can the pH have on a substrate?

A

May affect the protonation states of the substrate too

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3
Q

How does the temperature affect the enzyme?

A

Increase the flexibility in the protein backbone , becomes more dynamic , increased rate. Eventually too flexible and denatures

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4
Q

What are the two types of non- covalent regulators?

A
  • simple inhibition

- allosteric inhibition

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5
Q

What are the 3 types of simple , non - covalent regulation

A
  • competitive
  • non-competitive
  • uncompetitive
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6
Q

Is non- covalent regulation reversible?

A

yes

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7
Q

what is the effect of competitive inhibition on the Vmax?

A

nothing

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8
Q

What is the effect of competitive inhibition on the Km?

A

Km increases ( apparent Km)

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9
Q

What is the effect of competitive inhibition on the dissociation constant?

A

increases

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10
Q

What happens to the Lineweaver Burk plot with competitive inhibition?

A

Cross at the same point on the y axis

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11
Q

What is the mechanism of noncompetitive inhibition?

A
  • Binds to enzyme but not at active site
  • changes the shape of enzyme and active site
  • substrate cannot fit into active site
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12
Q

What is the effect of non - competitive inhibitor on the Vmax?

A

Vmax is reduced

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13
Q

What is the effect of the non - competitive inhibitor on the Km?

A

The Km is not affected

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14
Q

What form of the enzyme can thE non-competitive inhibitor effect?

A
  • Free enzyme

- ES complex

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15
Q

What affects are caused by non-competitive inhibition on the Lineweaver Burk plot?

A

Both cross the x axis at the same place

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16
Q

What is the mechanism of the uncompetitive inhibitor?

A

When the inhibitor binds only to the ES to make ESI

17
Q

Where is uncompetitive inhibition found?

A

With an enzyme that catalysis a 2 step reaction

18
Q

What effects doe uncompetitive inhibition have on the Km and Vmax?

A

both decreased

19
Q

what is the advantage of Allosteric inhibition over simple inhibition?

A

Highly sensitive and can drastically increase or decrease the product.

20
Q

What is the most common form of allosteric inhibition

A

non competitive

21
Q

Does allosteric inhibition follow the Michaelis Menton curve?

A

No , it gives a sigmoidal curve. Inhibitor or activator pushes the sigmoidal curve one way or another, pushing to higher of lower substrate concentrations

22
Q

what are the advantages of covalent regulation?

A

Dramatic activation or inactivation/can you completely switch it on or off

23
Q

What are the two types of covalent regulation?

A
  • reversible, inactivation or activated

- irreversible, enzyme may be activated by being cleaved

24
Q

How do you classify the 6 types of enzyme s

A
  1. Oxo-reductases
  2. Transferases
  3. Hydrolases
  4. lyases
  5. isomerases
  6. ligases
25
Q

What to measure in awn enzyme assay?

A

Initial product // disappearance of substrate

26
Q

An noncompetitive inhibitor

A
  • changes the shape of enzyme and active site

- does not have a structure like substrate

27
Q

What can a noncompetitive inhibitor do?

A
  • Bind to both the free enzyme and enzyme substrate complex
28
Q

Allosteric inhibition

A

Show co-operative binding.

Has binding sites and can switch between two forms ; active vs inactive

29
Q

Does allosteric inhibition reduced V or Vmax

A

reduces the rate but not the Vmax.

30
Q

Why do allosteric inhibitors have such a big effect on rate?

A

A small change In the inhibitor concentration gives a big inhibition

31
Q

what shape are allosteric proteins?

A

Allosteric proteins tend to be oligomeric

32
Q

Active form vs inactive form of allosteric inhibition

A

active form - bound in via the substrate. inactive , inhibitor bound to allosteric site

33
Q

What is a example of irreversible covalent enzymes?

A

proteases . synthesised as inactive precursors- Zymogens , then cleaved to produced the active enzyme

Biochemistry 1 BB10003 (18 decks)

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