Brainscape's Knowledge GenomeTM

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


See full index

1. BIOC 1301 S1 > Reaction Kinetics and Inhibition > Flashcards

Reaction Kinetics and Inhibition Flashcards

1
Q

What is the order of a reaction?

A

It tells you how much the concentration of a reactant affects the rate

Order corresponds to the molecularity of the reaction = the number of molecules that must simultaneously collide to generate a product

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

What is the individual order? Overall order? Rate equation?

A

Individual order - the power to which a concentration is raised in the rate equation
Overall order - the sum of the individual orders in the rate equation
Rate equation - rate = k[A][B]
k = rate constant

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

What is first order? Second order?

A

First - the rate is proportional to the concentration

Second - the rate is proportional to the square of the concentration

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

What was the first proposed equation?

A

E + S ⇌ ES ⇌ P + E

K1 - rate over first arrow
K2 - rate over second arrow
K-1 - rate coming back over first arrow

K2 is the rate determining step (slowest)

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

How was the Michaelis-Meuten equation derived?

A

To derive the equation you have to make an assumption and the equation will differ slightly based on which assumption you assume
There were 2 possible assumptions:

  1. Equilibrium assumption - E + S and ES are in equilibrium
  2. Steady state assumption - ES maintains a steady state, as [S] > [E], until [S] is exhausted

Steady State was used

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

What is the Michaelis-Menten equation?

A

Vo = Vmax[S] / Km + [S]

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

What is the Mechaelis constant?

A

Km = K-1 + K2 / K1

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

What is Vmax?

A

The maximal velocity/rate of a reaction, when the enzyme is completely saturated with its substrate in the ES form

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

What is Km?

A

Substrate concentration that gives you 1/2 Vmax

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

What does Km tells us?

A

Km tells us something about the affinity of the enzyme for the substrate:
Low Km = high affinity
High Km = low affinity

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

What kind of graph is produced when plotting [S] against Vo?

A

Rectangular Hyperbola

It has an asymptote

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

What is a measure of catalytic efficiency?

A

kcat/Km = specificity constant
Which is a useful indicator of relative catalytic efficiency

This ratio can’t be bigger than K1, most values are near the diffusion controlled limit of 10^8 to 10^9 M-1 s-1

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

What is kcat?

A

The turnover number - the number of reaction processes that each active site catalyses per unit of time

kcat = Vmax/[E]T

[E]T = total enzyme conc

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

What can be used to measure Km and Vmax?

A

A Lineweaver-Burke Plot
y = mx + c

1/Vo = Km/Vmax * 1/[S] + 1/Vmax

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

How to draw a lineweaver-burke plot?

A

Plot 1/V on the y axis

Plot 1/[S] on the x axis

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

What can we determine from a lineweaver-burke plot?

A 
Y-intercept = 1/Vmax
X-intercept = 1/Km

Slope = Km/Vmax

17
Q

What is used to provide the information for a lineweaver-burke plot?

A

Assays - used to measure how much an enzyme there is

Continuous - e.g. measuring absorbance in a spectrophotometer
Discontinuous - stopping the reaction and measuring
Coupled - measuring another reaction coupled to the reaction we want to measure

Quantified by taking the initial rate of reaction (tangent to a curve)

18
Q

What is the problem with steady state kinetics?

A

It doesn’t reveal the number of intermediates in the enzyme cataylsed reaction
Therefore intermediates have to be identified through the use of spectroscopic techniques

Knowledge of intermediates is essential to confirm/eliminate proposed mechanisms

19
Q

What are bisubstrate reactions?

A

Reactions with multiple substrates yeilding multiple products
e.g.
Sequential reactions occur via single displacements
AND
Ping pong reactions occur via double displacements

20
Q

What are some types of sequential reactions?

A

Ordered mechanism - complusary order of the substrate addition to the enzyme

Random mechanism - both binding sites are present on the free enzyme (any order)

21
Q

What are ping pong reactions?

A

Group-transfer reactions in which one or more products are released before all substrates have been added

The substrates don’t encounter each other on the surface of the enzyme

22
Q

What are some factors affecting enzymes?

A

Temperature
pH
Substrate concentration
Enzyme concentration

Inhibitor presence/concentration

23
Q

Describe the effect of temperature on enzymes?

A

Non-covalent interactions can break and the protein can denature - disrupting the active site

Thermophilic enzymes can survive above 100 degree
Our enzymes are mesophilic
Psychrophilic enzymes - exist in freezing temperatures

24
Q

What do inhibitors do? Types?

A

They decrease enzyme activity

Irreversible - covalently binds so tightly to the enzyme it permenantly blocks enzyme activity

Reversible - diminishes activity but can be removed

25
Q

Types of reversible inhibitors?

A

Competitive - competes with the substrate for the binding site on the enzyme

Uncompetitive - Inhibitor binds to the ES complex

Non-competitive (mixed) - Can bind to both the E or the ES complex

26
Q

Describe competitive inhibition? Examples?

A

The inhibitor binds to the enzyme forming an EI complex
E.g. malonate is a competitive inhibitor for succinate going to fumarate
AND
using transition state analogs to inhibit the affects of HIV/AIDs

27
Q

What equations can work out Ki for competitive inhibition?

A

Vo = Vmax[S]/ aKm + [S]

a = 1 + [I]/Ki

a = apparent

28
Q

How does competitive inhibition affect Vmax and Km?

A

Vmax - unchanged

Km - increases

29
Q

Describe uncompetitive inhibition?

A

Inhibitor binds to the ES complex forming an ESI complex

30
Q

What equations can work out Ki for uncompetitive inhibition?

A

Vo = Vmax[S]/ Km + a’[S]

a’ = 1 + [I]/K’i

31
Q

How does uncompetitive inhibition affect Vmax and Km?

A

Vmax - Decreases

Km - Decreases

32
Q

Describe noncompetitive inhibition?

A

Can bind to both the E or the ES complex, forming either EI complex or a ESI complex

33
Q

What equations can work out Ki for noncompetitive inhibition?

A

Vo = Vmax[S]/ aKm + a’[S]

a = 1 + [I]/Ki 
a' = 1 + [I]/K'i
34
Q

How does noncompetitive inhibition affect Vmax and Km?

A

Vmax - Decreases

Km - Increase or decrease

35
Q

What is pure noncompetitive inhibition?

A

Only Vmax is affected and aKm remains unchanged

Said to be similar to irreversible inhibition

1. BIOC 1301 S1 (28 decks)

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