Brainscape's Knowledge GenomeTM

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


See full index

Biochem > 2: Enzymes > Flashcards

2: Enzymes Flashcards

1
Q

Key points to remember about enzymes (7)

A

1) Lower the activation energy
2) Increase the rate of the reaction
3) Do not alter the equilibrium constant
4) Are not changed or consumed in the reaction (which means that they will appear in both the reactants and products).
5) Are pH- and temperature-sensitive, with optimal activity at specific pH ranges and temperatures
6) Do not affect the overall G of the reaction
7) Are specific for a particular reaction or class of reactions

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

Enzyme classes (6)

A

“LIL HOT”

1) Ligases
2) Isomerases
3) Lyases
4) Hydrolases
5) Oxidoreductases
6) Transferases

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

Describe oxidoreductases

A

1) catalyze oxidation-reduction reactions
2) often have a cofactor that acts as an electron carrier (NAD+ or NADP+)
3) in reactions catalyzed by these, the electron donor is known as the reductant and the electron acceptor is known as the oxidant.

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

________ catalyze the movement of a functional group from one molecule to another.

A

Transferases

i.e. in protein metabolism, an aminotransferase can convert aspartate and alpha-ketoglutarate, as a pair, to glutamate and oxaloacetate by moving the amino group from aspartate to alpha-ketoglutarate.

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

Give an example of transferases.

A

Kinases, catalyzing the transfer of a phosphate group, generally from ATP, to another molecule.

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

_______ catalyze the breaking of a compound into two molecules using the addition of water.

A

Hydrolases

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

One of the most common hydrolases is ________, which cleaves a phosphate group from another molecule.

A

phosphotases

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

Give 4 examples of hydrolases and their functions.

A

1) Phosphatases — cleave a phosphate group
2) Peptidases — break down proteins
3) Nucleases — break down nucleic acids
4) Lipase — break down lipids

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

_____ catalyze the cleavage of a single molecule in two products.

  • do NOT require water as a substrate
  • do NOT act as oxidoreductases
A

Lyases

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

Because most enzymes also catalyze the reverse of their specific reactions, the synthesis of the two molecules into a single molecule may also be catalyzed by a _____.

A

lyase

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

_______ catalyze the rearrangement of bonds within a molecule.

A

Isomerases

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

____ can also be classified as oxidoreductases, transferases or lyases, depending on the mechanism of the enzyme.

A

Isomerases

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

Isomerases also catalyze reactions between _______ as well as _______ isomers.

A

stereoisomers, constitutional

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

____ catalyze addition or synthesis reactions, generally between large similar molecules and often require ATP.

A

Ligases

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

Synthesis reactions with smaller molecules are generally accomplished by _____

A

lyases

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

Ligases are most likely to be encountered in _______ synthesis

A

Nucleic acid

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

A(n) ______ reaction requires energy input (G > 0)

A

energonic

-these reactions require energy as they proceed

18
Q

A(n) ______ reaction id one in which energy is given off (G < 0)

A

exergonic

-these reactions release energy as they proceed

19
Q

Describe the very important characteristic of enzymes

A
  • They do not alter the overall free energy change for a reaction
  • Nor do they change the equilibrium of a reaction
  • They affect the rate (kinetics) at which the reaction occurs, thus they affect how quickly a reaction gets to equilibrium but not the actual equilibrium state
  • enzymes ensure that many important reactions can occur in a reasonable amount of time in biological systems
  • unchange by the reaction therefore far fewer copies of the enzyme are required relative to the overall amount of substrate because one enzyme can act on many, many molecules of substrate over time.
20
Q

How do catalysts exert their affects on a reaction?

A

They lower the activation energy of a reaction
(make it easier for the substrate to reach the transition state)

Ex. Imagine having to walk to the other side of a tall hill. The only way to get there is to climb to the top of the hill and then walk down to the other side–but wouldn’t it be easier if the top of the hill was cut off so one wouldn’t have to climb so high?

21
Q

How do enzymes function as biological catalysts?

A

Catalysts are characterized by two main properties:
1) they reduce the activation energy of a reaction, thus speeding up the reaction.

2) Enzymes improve the environment in which a particular reaction takes place, which lowers the activation energy. They are also regenerated at the end of the reaction to their original form.

22
Q

What is enzyme specificity?

A

Enzyme specificity refers to the idea that a given enzyme will only catalyze a given reaction or type of reaction.

For example, serine/threonine-specific protein kinases will only place a phosphate group onto the hydroxyl group of a serine or threonine residue.

23
Q

What are the names and functions of the six different classes of enzymes?

A

“LIL HOT”

1) Ligase: addition or synthesis reactions, generally between large molecules; often require ATP
2) Isomerase: Rearrangement of bonds within a compound
3) Lyase: Cleavage of a single molecule into two products, or synthesis of small organic molecules
4) Hydrolase: Breaking of a compound into two molecules using the addition of water
5) Oxidoreductase: Oxidation-reduction reactions (transferring electrons)
6) Transferase: Movement of a functional group from one molecule to another

24
Q

In what ways do enzymes affect the thermodynamics vs the kinetics of a reaction?

A

Enzymes have no effect on the overall thermodynamics of the reaction
They have NO effect on the G or H of the reaction, although they do lower the energy of the transition state, thus lowering the activation energy. However, enzymes have a profound effect on the kinetics of a reaction. By lowering activation energy, equilibrium can be achieved faster (although the equilibrium position does not change).

25
Q

The molecule upon which an enzyme acts is known as its _______.

A

substrate

26
Q

The physical interaction between these two is referred to as the ____________.

A

enzyme-substrate complex

27
Q

The ______ is the location within the enzyme where the substrate is held during the chemical reaction.

A

active site

28
Q

_______, _______, and transient _________ within the active site all stabilize the spatial arrangement and contribute to the efficiency of the enzyme.

A

Hydrogen bonding, ionic interactions, covalent bonds

29
Q

What does the Lock and Key Theory suggest?

A

It suggests that the enzymes active site (lock) is already in the appropriate conformation for the substrate (key) to bind.
No alteration of the tertiary/quaternary structure is necessary upon binding of the substrate.

30
Q

Describe the Induced Fit Model

A

starts with a substrate and enzyme active site that do not fit together
however, once the substrate is present and ready to interact with the active site, the molecules find that the induced form (transition state) is more comfortable for both of them. Thus, the shape of the active site becomes truly complementary only after the substrate begins binding to the enzyme.

A substrate of the wrong type will not cause a conformational shift in the enzyme. Thus, the active site will not be adequately exposed, the transition state is NOT preferred, and no reaction occurs.

31
Q

Enzymes tend to require nonprotein molecules called _______ or _______ to be effective.

A

coenzymes or cofactors

32
Q

Enzymes without their cofactors are called __________

A

Apoenzymes

33
Q

Enzymes containing their cofactors are called ________.

A

Holoenzymes

34
Q

How are coenzymes attached?

A

In a variety of ways: From weak noncovalent interactions to strong covalent ones.

35
Q

Tightly bound cofactors or coenzymes that are necessary for enzyme function are known as ___________.

A

prosthetic groups

36
Q

_______ are generally inorganic molecules or metal ions, and are often ingested as dietary minerals.

A

Cofactors

37
Q

______ are small organic groups, the vast majority of which are vitamins or derivatives of vitamins such as NAD+, FAD and coenzyme A.

A

Coenzymes

38
Q

The water-soluble vitamins include the ________ vitamins and _________ and are important coenzymes that must be replenished regularly cause they are easily excreted.

A

Vitamin B complex, ascorbic acid/Vitamin C

39
Q

The fat-soluble vitamins (________) are better regulated by partition coefficients, which quantify the ability of a molecule to dissolve in a polar vs. nonpolar environment.

A

ADEK

40
Q 
B Vitamins:
B1: 
B2:
B3:
B5:
B6:
B7:
B9:
B12:
A 
B1: Thiamine
B2: Riboflavin
B3: Niacin
B5: Pantothenic Acid
B6: Pyridoxal phosphate
B7: Biotin
B9: Folic Acid
B12: Cyanocobalamin

Biochem (4 decks)

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