Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

BMS 102 > Enzymes > Flashcards

Enzymes Flashcards

(59 cards)

Start Studying
1
Q

What is an enzyme

A

A highly specific protein that functions as a biological catalyst in order to speed up biochemical reactions

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

One of the fastest enzymes known is

A

Carbonic anhydrase

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

What is enzyme specificity due to?

A

Precise interactions of substrate with enzyme (precision due to 3D structure of enzyme)

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

What are the six classes of enzymes

A
  1. oxidoreductases
  2. Transferases
  3. Hydrolases
  4. Lyases
  5. Isomerases
  6. Ligases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Oxidoreductases

A

Catalyze oxidation-reduction reactions

  • transfer electrons between molecules
    ex. lactate dehydrogenase

*these reactions require the coenzyme NAD

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

Transferases

A

Catalyze the transfer of functional groups between molecules

-ex. alanine transaminase

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

Hydrolyases

A

Catalyze hydrolysis by cleaving molecules by the addition of water
ex. trypsin and pyrophosphatase

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

Lyases

A

Catalyze the addition of atoms or functional groups to a double bond OR removes them to form a double bond

ex. fumarase

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

Isomerases

A

Catalyze the movement of functional groups within a molecule
~generally the simplest enzymatic reactions as only 1 substrate and 1 product
“iso” = same, so within the SAME molecule

ex. alanine racemase

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

Ligases

A

Catalyze bond formation or joining two molecules at the expense of ATP

ex. DNA ligase or glutamine synthetase

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

What is an enzyme without its co-factor?

A

An apoenzyme

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

What is the name of a complete catalytically active enzyme?

A

A holoenzyme

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

Co-factors can be:

A
  1. small organic molecules derived from vitamins called coenzymes or
  2. metals
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are tightly bound coenzymes called?

A

Prosthetic (helper) groups

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

Enzymes may speed up a chemical reaction but properties of the reaction (for example if it occurs at all) depends on _____

A

Free energy differences

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

What is free energy (G)

A

Measure of useful energy

-the ability to do work

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

What is the free energy change of a reaction? delta G

A

Informs us as to whether a reaction can take place spontaneously

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

A reaction can take place spontaneously is delta G is…

A

Negative (exergonic)

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

A reaction cannot take place spontaneously if delta G is…

A

Positive (endergonic)

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

When is delta G zero?

A

At equilibrium there is no net change in concentration of products and reactants, so delta G is 0

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

T/F delta G provides information about the rate of a chemical reaction

A

False

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Can enzymes alter the equilibrium of a chemical reaction

A

No

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

X‡ is?

A
  • an unstable arrangement of atoms – chemical bonds are in the process of being broken or formed
  • called a Transition State – it has higher ∆G than does S or P
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the function of an enzyme?

Study These Flashcards
A

lower the ∆G‡ OR facilitate the formation of the transition state

25
What is at the heart of enzyme catalysis
Stabilization of the transition state
26
Enzyme do's
- lower the ∆G‡ for the reaction - Stabilise the Transition State - Make the forward reaction much more favourable
27
Active site
- Is a 3D cleft or crevice - Small part part of the total volume of an enzyme - The substrates bind to the active site on an enzyme by multiple weak attractions - Binding specificity depends on precisely defined arrangements of atoms in the active site
28
Lock and Key Theory
Enzyme is a rigid template (lock) and the substrate is a matching key - Active site of the enzyme is complementary in shape to the substrate - This theory says that the active site resides are completely immobile
29
Induced fit theory
This theory takes the flexible nature of protein structure into account -The active sites some enzymes assume a shape that is complementary to that of the substrate only AFTER the substrate has been bound *INDUCED FIT b/c the enzyme and substrate slightly change shape to suit each other after they bind
30
Binding energy...when is maximal binding energy released
- The weak interactions between complementary enzyme and substrate - Only when the enzyme facilitates formation of the transition state
31
Transition state analogues
- Potent inhibitors of enzymes | - Very unstable
32
Kinetics
Study of the rates of chemical reactions
33
Velocity (V)
The quantity of reactant, A, that disappears in a specified unit of time, t. Velocity is directly related to concentration of A by a constant, k, called the rate constant V=k[A]
34
First-order reactions
Reactions in which V is directly proportional to reactant concentration - have the unit s^-1 - the initial rate of reaction doubles when the reactant is doubled
35
Second-order reactions
Involve two reactants and have the units M^-1s^-1 | -the initial rate of the reaction quadruples when the reactant is doubled
36
Michaelis-Menten Model
Initial velocity rises linearly as [S] increases and then begins to level off (plateau) v0 (initial velocity)= the rate of increase in product with time when [P] is low --measured for each substrate concentration by measuring the rate of product formation before P accumulates
37
Km
Michaelis constant... is unique to each enzyme and independent of enzyme concentration Is equal to substrate concentration at which the reaction velocity is half is maximum value (half of the active sites are filled) values depend on environmental conditions
38
Vmax
Directly dependent on enzyme concentration and can only be attained when all the enzyme is bound to substrate -tells us about the turnover number of an enzyme
39
Low Km value
Tight substrate binding
40
Turnover number of an enzyme
Number of substrate molecules that an enzyme can convert into product per unit time when the enzyme is fully saturated with substrate Kcat
41
Kcat/Km =
Measure of catalytic efficiency
42
Lineweaver-Burk plot
Graph of the reciprocal of both sides of the michaelis-menten equation
43
Sequential reactions
All substrates must bind to enzyme before any product released *can either be ordered or random
44
Double displacement reactions
One or more products are released before all substrates bind enzymes -substrates/products bounce on and off an enzyme (like a ping-pong ball)
45
Allosteric enzymes
Enzymes that regulate the flux of biochemical compounds in metabolic pathways - Have a second regulatory site (allosteric site), which is distinct from the active site - catalyze the committed step of metabolic pathways - DO NOT CONFORM TO MICHAELIS-MENTEN KINETICS - activators can lower Km, inhibitors can raise Km
46
How do feedback inhibitors work?
They bind to a distinct regulatory site on the allosteric enzyme
47
Phosphofructokinase
Catalyzes the committed step in glycolysis | -ATP acts as an allosteric inhibitor while fructose 1,6-biphosphate acts as an allosteric activator
48
What are the four mechanisms that enzymes use to form the transition state
1. covalent catalysis 2. acid-base catalysis 3. metal ion catalysis 4. stabilization of the transition state
49
Covalent catalysis
Active site contains a reactive group (usually powerful nucleophile) that becomes temporarily covalently modified during catalysis.
50
Acid-base catalysis
A molecule other than water plays the role of a proton donor or acceptor (e.g. chymotrypsin uses a histidine residue as a base catalyst to enhance nucleophilic power of serine
51
Metal ion catalysis
1. can bind substrates to increase binding energy 2. may generate a nucleophile by increasing acidity of a nearby molecule 3. stabilize or shield negative charges by acting as an electrophilic catalyst
52
Metalloenzymes
Contain tightly bound metal ions (usually Fe 2+, Fe3+, Zn 2+)
53
Metal activated enzymes
Contain loosely bound metal ions (usually Na+, K+, Mg 2+, or Ca2+)
54
What is the optimal pH for most enzymes?
Between 5 and 9
55
3 main types of reversible inhibition
1. competitive 2. uncompetitive 3. noncompetitive
56
Competitive inhibition
- the inhibitor usually resembles the substrate and binds only to free enzyme (not the ES complex) - competitive inhibitor reduces the proportion of enzyme molecules bound to the substrate thus decreasing catalysis - Has no effect on Vmax but increase Km
57
Uncompetitive inhibition
- inhibitor binds only to the ES complex NOT the free enzyme - decreases Vmax and decreases Km
58
Noncompetitive inhibition
- inhibitor can bind simultaneously with the substrate to the enzyme at different binding sites - can bind to both free enzyme and the enzyme-substrate complex - decreases Vmax and Km does not change
59
Irreversible inhibition
-inhibitors form stable covalent bonds with the enzyme

BMS 102 (5 decks)

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