Brainscape's Knowledge GenomeTM

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


See full index

BIOSCI106 2017 SEM 2 > Enzymes > Flashcards

Enzymes Flashcards

1
Q

How do enzymes work to lower the energy to make products faster?

A

They lower the activation energy by forming an enzyme-substrate complex

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

What are the 3 substrate recognition hypotheses?

A
  1. Lock and key
  2. Induced fit - when the substrate binds to the enzyme it change shape to fit around it
  3. Conformational selection - when the right enzyme shape and the wrong shape are in equilibrium with each other
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe the binding energy of a reaction:

A

The free energy that is released by the formation of weak bonds between the substrate and the enzyme. These interactions are maximised when the substrate is in the transition state - tightest interaction between enzyme and substrate. However the transition state is the least stable chemical form of the substrate

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

What is the rest of the amino acids for in an enzyme that are not involved in the active site?

A
  1. Positioning the active site residues correctly, sometimes in energetically unfavourable positions
  2. Providing the correct microenvironment in the active site e.g shifting of pKa values.
  3. Provides other sites for recognition and control e.g allostery
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are organic cofactors known as?

A

Co enzymes

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

What are the 2 types of enzymes?

A
  1. Enzymes made completely out of protein and fully active
  2. Enzyme that needs an associated non-protein component in order to be a catalyst. The protein alone is called ‘apo’ enzyme and the whole enzyme is known as ‘holo’ enzyme
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the difference between a prosthetic group and a coenzyme/cofactor?

A

Prosthetic groups are bound all the time whereas cofactors and coenzymes can bind and dissociate during the catalytic cycle

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

What are the 3 ways that enzymes can be regulated?

A
  1. Proteolysis of proenzymes is a one-way “on” switch
  2. Transient modification e.g phosphorylation is a two way switc
  3. Allostery is a graded response to either substrates or other non-covalently bound regulatory molecules.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What does a small kd imply?

A

Tight binding

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

What is the michleis menten eqn?

A

V = (vmax [s]) / (Km + [s])

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

What are the 4 assumptions for the mechalis meneten eqn?

A
  1. Catalysis is the slowest rate limiting step ka>kcat
  2. There is much more substrate than enzyme
  3. The conc of ES is constant
  4. The reverse reaction is negligible
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the features of the lineweaver burk transformation?

A

Axis are 1/v and 1/[s]. The point of intersection between the ine and the 1/v is the 1/vmax and the intersection between the line and 1/[s] is -1/Km.

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

What are the 3 types of reversible inhibitors and what is the type of unreversible inhibitor?

A
  1. Competitive
  2. Non-competitive
  3. Uncompetitive
  4. Covalent modification of enzyme
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

The smaller the ki value…..

A

The better the inhibitor

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

Describe the type of inhibition: competitive

A

Inhibitors compete for the active site so they must be chemically similar to the enzymes substrate. The decrease Kcat but inhibition can be overcome by increased substrate conc

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

Describe the type of inhibition: non-competitive

A

Inhibitors bind to a site that is distant from the active site which is not dependent on the formation of the enzyme substrate complex, it acts by reducing Kcat.

17
Q

Describe the type of inhibition: uncompetitive

A

Inhibitors can bind to another site which is only accessible after the substrate has bound to the enzyme. It cannot be overcome by adding more substrate

18
Q

How does this type of inhibition affect Km/Vmax and what is the apparent Km/Vmax: competitive

A

The Vmax stays the same but -1/Km increases so the real Km decreases

Km app = Km (1 + [I]/Ki)

19
Q

How does this type of inhibition affect Km/Vmax and what is the apparent Km/Vmax: non-competitive

A

1/Km stays the same but 1/Vmax increases so the real Vmax decreases

Vmax app = Vmax / (1 + [I]/Ki)

20
Q

How does this type of inhibition affect Km/Vmax and what is the apparent Km/Vmax: uncompetitive?

A

Both 1/vMax and -1/Km increase

Vmax app = Vmax / (1 + [I]/Ki)
Km app = Km / (1 + [I]/Ki)

21
Q

How can we calculate Ki?

A

By using a secondary plot - with either the slope (competitive) or y axis intercepts (non-competitive) plotted against [I]. The intercept with the x axis will then be the Ki

22
Q

What is the hill eqn?

A

V = (Vmax [s] ^h) / (K + [s]^h)

23
Q

What does the hill plot show us?

A

The slope is h and the bigger h is, the more cooperative the process. The point of intersection is log k/h

24
Q

What is the T state?

A

High k so lower affinity for s

25
Q

What is the R state?

A

Low k so higher affinity for s

26
Q

What is homotropic allostery?

A

There is a conformational change around the binding site when the substrate comes in which leads to a conformational change in the subunit from T to R, which causes the same chnage in the other subunit so now there are 2 R’s

27
Q

What is the biological importance of allosteric enzymes?

A

The rate of reaction can be very sensitive to [s] and so they can essentially act as switches.

28
Q

What is heterotropic enzymes?

A

They are chemically unrelated to the substrate. They can be activators (positive heterotrophic effects) or inhibitors (negative heterotrophic effects). They allow for feedback control. There is a conformational change around the binding site when the inhibitor comes in which leads to a change in the subunit where the inhibitor is bound. This leads to a conformational change in the other subunit so that it has a lower affinity for [s]

29
Q

Why does ATP hydrolysis release energy?

A
  1. Resonance stabilisation of free phosphate is better than for tri-phosphate
  2. Electrostatic repulsion of triphosphate is energetically unfavourable
  3. Water can more effectively hydrate free phosphate than triphosphate
30
Q

How does coupling an otherwise unspontaneous reaction with ATP make it happen?

A

Some reactions in metabolism may not be spontaneous i.e G > 0. These reactions cannot happen even in the presence of an enzyme. Coupling the reaction with the hydrolysis of ATP to the unfavourable reaction makes the overall reactions spontaneous so the combined G < 0.

31
Q

What is an example of a 5 membered ring?

A

Ribose

32
Q

What is an example of a 6 membered ring?

A

Glucose

33
Q

Whats the difference between d/l isomers?

A

D isomers have the last OH group on the right and L have it on the left. D isomers have the CH2OH facing up and l have it facing down.

34
Q

What are steroisomers?

A

Same molecular formula, different arrangement in space

BIOSCI106 2017 SEM 2 (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions