Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biochemistry Pt. 2 > Lecture 11 - Enzyme Regulation > Flashcards

Lecture 11 - Enzyme Regulation Flashcards

1
Q

Basic concept of zymogen

A

The active site is not formed correctly until there’s a proteolytic cleavage at a specific activation site on the chain.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How is a zymogen converted into an active enzyme?

A

When triggered, proteolytic cleavage occurs rapidly, resulting in nearly instant activation of enzyme activity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Prothrombin

A

The zymogen form of thrombin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

True or false: Thrombin is a serine protease.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Where is thrombin made?

A

On a membrane surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How many proteolytic cleavages need to be made in order to activate thrombin?

A

Two

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Which cleavage activates thrombin that has been released from the membrane?

A

The peptide bond that allows isoleucine 16 to swing in and form a H-bond with aspartate 194 in order to put the serine 195 in the right position to be an active nucleophile

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

True or false: Activation of thrombin is reversible.

A

False

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How many polypeptide chains does mature thrombin have and what kind of bond holds them together?

A

It has two chains (a light chain, residues 1-15, and a heavy chain, residues 16 to the end) and they are linked by a disulfide bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

True or false: The mature form of thrombin is water soluble.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the post-translational modification that is made to prothrombin that allows it to bind to the membrane?

A

y-carboxylation of particular glutamate residues on the N-terminus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why does that modification allow prothrombin to bind to the membrane?

A

y-carboxy-glutamate has an extra negative charge allowing it to bind positively charged calcium ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What does the binding of calcium ions allow prothrombin to do?

A

It exposes hydrophobic residues that can bind the membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the cofactor for the carboxylation of the N-terminus of prothrombin?

A

Vitamin K

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What do Vitamin K antagonists do?

A

They interfere with the carboxylation of prothrombin, therefore it doesn’t bind to membranes well and it will not form active thrombin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Why does prothrombin need to bind a membrane surface?

A

The activating protease for thrombin exists on the membrane and prothrombin must be near this enzyme in order to be activated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What does the activating protease for thrombin do?

A

It releases thrombin from the membrane surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does thrombin catalyze?

A

The conversion of soluble fibrinogen to insoluble fibrin that will form a blood clot

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How do protein inhibitors work?

A

They bind so tightly to a given enzyme that the enzyme-inhibitor complex as a whole is degraded

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is an example of an enzyme-inhibitor complex?

A

Thrombin-antithrombin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is heparin and what does it do?

A

It is a commonly prescribed short acting anticoagulant that promotes antithrombin-thrombin complex formation

22
Q

What is a common vitamin K antagonist?

A

Warfarin

23
Q

Elastase inhibitor

A

Alpha-1-antitrypsin or alpha-1-antiproteinase

24
Q

Elastase

A

A protein that degrades elastin

25
Q

Elastin

A

A protein in lung tissue that gives it flexibility

26
Q

What does smoking cause?

A

Oxidation of alpha-1-antitrypsin

27
Q

What are the consequences of oxidized alpha-1-antitrypsin?

A

It does not effectively inhibit elastase, elastase cleaves elastin without regulation and this causes lung scarring and emphysema

28
Q

What does protein phosphorylation or dephosphorylation do?

A

It modifies the charge of an amino acid (like serine, threonine, or tyrosine) residue and if that residue is in or near the active site, the activity of the enzyme may be changed (increased or decreased)

29
Q

What are the different kinds of enzyme inhibitors?

A

Competitive, noncompetitive, irreversible, allosteric

30
Q

Competitive inhibitors

A

Binding site only; Km in presence of inhibitor will increase (1/Km will decrease); sometimes the immediate product of a reaction can compete with the substrate

31
Q

Non-competitive inhibitors

A

Do not interfere with substrate binding; does not change Km, but they will decrease vmax (1/vmax will increase); interfere with catalytic machinery

32
Q

Vmax is proportional to…

A

the amount of enzyme present

33
Q

Irreversible inhibitors

A

Non-competitive inhibitors that bind enzymes and do not release them; this decreases the amount of enzyme present and decreases the vmax

34
Q

True or false: Inhibitors showing a drop in vmax can be reversible or irreversible.

A

True

35
Q

True or false: Changes in the substrate concentration do not change enzyme activity.

A

False

36
Q

Allosteric enzymes

A

Usually contain multiple subunits; does not usually follow Michaelis-Menten kinetics; can define an “apparent” Km; usually have binding sites for affector molecules; often regulate a reaction pathway

37
Q

True or false: Allosteric enzymes are very sensitive to substrate.

A

True

38
Q

True or false: Allosteric enzymes are loosely regulated by substrate concentration.

A

False

39
Q

Example of an allosteric enzyme

A

Phosphofructosekinase 1 (PFK1)

40
Q

Allosteric enzymes are often where in a dedicated reaction pathway?

A

At the beginning

41
Q

What is an allosteric activator of PFK1?

A

AMP

42
Q

What is an allosteric inactivator of PFK1?

A

ATP

43
Q

Why is PFK1 inhibited by high amounts of ATP?

A

High amounts of ATP signal that the cell is energy rich and glycolysis should not continue

44
Q

Why is PFK1 activated by high amounts of AMP?

A

High amounts of AMP signal that the cell is energy poor and that glycolysis should continue

45
Q

How many catalytic sites does PFK1 have?

A

Two

46
Q

What does the Ki mean?

A

It marks the affinity of a substrate for an inhibitor.

47
Q

Allosteric activators drive enzymes to what form?

A

Relaxed

48
Q

Allosteric inhibitors drive enzymes to what form?

A

Taut

49
Q

Where do ATP and AMP bind PFK1?

A

Allosteric sites

50
Q

Feedback inhibition

A

Typically the product inhibiting an earlier reaction

Biochemistry Pt. 2 (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions