Brainscape's Knowledge GenomeTM

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


See full index

BIOCHEM 1 > 6 - THE BEHAVIOR OF PROTEINS: ENZYMES > Flashcards

6 - THE BEHAVIOR OF PROTEINS: ENZYMES Flashcards

1
Q

a biological catalyst

A

Enzyme

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

with the exception of some RNA’s that catalyze their own splicing, all enzymes are?

A

Proteins

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

can increase the rate of a reaction by a factor of up to 10^20 over an uncatalyzed reaction

A

Enzymes

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

some enzymes are so specific that they catalyze the reaction of only one stereoisomer; others catalyze a family of similar reactions

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

rate of reaction depends on its activation energy, DG

A

an enzyme provides an alternative pathway with a lower activation energy

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

most important function of proteins; performed by the protein, enzyme

A

Catalysis

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

highly specific; can distinguish isomers of a given compound

A

Enzymes

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

Biochemical reaction rates increase with temperature up to a point, but are limited due to enzyme denaturation, thermal inactivation of biomolecules, and the need to operate within an optimal temperature range for living organisms. Beyond these limits, reaction rates decrease as enzymes lose their functionality and other biological structures become compromised.

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

What are the two models that were developed to describe the formation of the enzyme-substrate complex?

A

Lock-and-key model
Induced fit model

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

substrate binds to that portion of the enzyme with a complementary shape; shape of the substrate and the conformation of the active site are complementary to one another

A

Lock-and-key model

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

binding of the substrate induces a change in the conformation of the enzymes that results to a complementary fit

A

Induced fit model

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

enzyme: undergoes a conformational change upon binding to the substrate

shape: active site becomes complementary to the shape of the shape substrate only after the substrate binds to the enzyme

A

Induced-fit model

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

What happens after the enzyme-transition complex is formed?

A

Catalysis occurs

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

In the complex:

S: bound close to atoms and is placed in the correct orientation with respect to the atoms with which it is to react; both proximity and orientation speed up the reaction

As some bonds are broken and new ones are formed, S —> product

Enzyme then S —> product

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

study on the formation of product from substrate

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q
  • catalyzes preferential hydrolysis of peptide bonds at residues containing aromatic side chains
  • cleaves at other sites (lys, his, and gln) at relatively lower frequency
  • catalyzes hydrolysis of ester bonds
A

Chymotrypsin

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

during hydrolysis of p-nitrophenyl ester by chymotrypsin,

A
  • rate is dependent on the substrate
  • at low [S], rxn rate increases with increasing [S]
  • at higher [S], rxn rate changes very little, and a max. rate is reached
  • graph: hyperbolic
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

carbamoyl phosphate + aspartate –> carbamoyl aspartate + hydrogen phosphate

  • the 1st step in he pathway leading to the formation of CTP and UTP, which are ultimately needed for biosynthesis of RNA and DNA
  • rxn rate also depends on [S] which is asp; graph is sigmoidal
A

Aspartate transcarbamoylase (ATCase)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q
  • an allosteric protein
  • similar to the kinetic behavior of hemoglobin
  • allosteric proteins -proteins in which subtle changes at one site affect structure and function at another site
A

ATCase

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

non-allosteric proteins

A

Chymotrypsin and myoglobin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q
  • 1913, Lenor Michealis and Maud Menten
  • basic model for nonallosteric enzymes
A

Michealis-Menten

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

Enzymatic conversion of a substrate to a product,

A

S —> P

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

When the rate of the rxn is half its max. value, the substrate conc is equal to the Michealis constant

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

a substance that interferes with the action of an enzyme and slows the rate of a reaction; decreases the rate of an enzyme-catalyzed reaction

A

Inhibitor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

a substance that binds to an enzyme to inhibit it but can be released

A

Reversible inhibitor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What are the two reverse inhibitors?

A

Competitive and noncompetitive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

binds to the active (catalytic) site and blocks access to the substrate

A

Competitive inhibitor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

compete with the substrate for binding to the enzyme’s active site; block the S access to it, thus competing with S for the E active site

A

Competitive inhibitor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

bind to a site other than the active site, causing a change in the enzymes in the enzyme’s shape and function

cannot be overcome by increasing substrate conc

A

Noncompetitive inhibitor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

binds to a site other than the active site; inhibits the enzyme by changing its conformation

A

Noncompetitive inhibitor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

a substance that causes inhibition that cannot be reversed; usually involves the formation/breaking of covalent bonds to or on the enzyme

A

Irreversible inhibitor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

similar to noncompetitive, but binding of inhibitor affects binding of S and vice versa

A

Mixed competitive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

bind only to the enzyme-substrate complex, preventing the complex from releasing products

A

Uncompetitive inhibitors

34
Q

What are the six major classes of enzymes?

A
  1. Oxidoreductases (EC 1)
  2. Transferases (EC 2)
  3. Hydrolases (EC 3)
  4. Lyases (EC 4)
  5. Isomerases (EC 5)
  6. Ligases (EC 6)
35
Q

systematically governs enzymes classification and nomenclature

A

Enzyme commission (EC)

36
Q
  • catalyze oxidation-reduction reactions, where electrons are transferred from one molecule (the reductant) to the (the oxidant)
  • e.g. alcohol dehydrogenase (EC 1.1.1.1)
A

Oxidoreductases (EC 1)

37
Q
  • transfer functional grps (e.g., a phosphate, methyl, or glycosyl grp) from one molecule to another
  • e.g. hexokinase (EC 2.7.1.1)
A

Transferases

38
Q
  • catalyze the hydrolysis of various bonds, breaking molecules down using water
  • e.g. lipase (EC 3.1.1.3)
A

Hydrolases

39
Q
  • catalyze the addition/removal of grps to form double bonds or break double bonds w/o hydrolysis or oxidation
  • e.g. pyruvate decarboxylase (EC 4.1.1.1)
A

Lyases (EC 4)

40
Q
  • catalyze the rearrangement of atoms within a molecule, facilitating structural changes (isomerization)
  • e.g. phosphoglucose isomerase (EC 5.3.1.9)
A

Isomerases (EC 5)

41
Q
  • catalyze the joining of two molecules with the formation of new chemical bonds, usually accompanied by the hydrolysis of ATP
  • e.g. DNA ligase (EC 6.5.1.1)
A

Ligases (EC 6)

42
Q

EC X.X.X.X

A

X = class, subclass, sub-sub-class, specific enzyme

43
Q

refers to an enzyme that breaks down sucrose

A

Sucrase

44
Q

The binding of oxygen by myoglobin is an example of a [] and is a []

A

non-allosteric behavior; non-allosteric protein

45
Q

the binding of oxygen by hemoglobin is an example of [] and is an []

A

allosteric behavior; allosteric protein

46
Q

What are the examples of allosteric proteins?

Their behaviors exhibit cooperative effects caused by subtle changes in quaternary structure

A

ATCase and hemoglobin

47
Q

catalyzes the 1st step in a series of reactions in which the end product is cytidine triphosphate (CTP), a nucleotide triphosphate needed to make RNA and DNA

A

ATCase

48
Q

are energetically costly and involve many steps

A

pathways that produce nucleotides

49
Q

an excellent example of how such a pathway is controlled to avoid the overproduction of such compounds

A

The reaction catalyzed by aspartate transcarbamoylase

50
Q

an efficient control mechanism because the entire series of reactions can be shut down when an excess of the final product exists, thus preventing the accumulaiton of intermediates in the pathway

A

Feedback inhibition

51
Q

study on the reaction catalyzed by ATCase leads eventually to the production of CTP

A
52
Q

an inhibitor of ATCase; an example of feedback inhibition (end-product inhibition), in which the end product of the sequence of reactions inhibits the first reaction in the series

A

CTP

53
Q

an oligomer whose biological activity is affected by other substances binding to it; change the enzyme’s activity by altering the conformation(s) of its quaternary structure

A

allosteric enzyme

54
Q

a substance that modifies the behavior of an allosteric enzyme

A

allosteric effector

55
Q

an allosteric effector can be?

A

allosteric inhibitor
allosteric activator

56
Q

Two principal models for the behavior of allosteric enzymes?

A

Concerted model and sequential model

57
Q

The downstream products combined to the regulatory site causing the enzyme to change shape and prevent it from binding to its substrate; causes the entire pathway to halt and new products are no longer formed

Conversely, when the amount of downstream product gets too low, the enzymes interact with their usual substrates and begin forming their usual products again

A
58
Q

Feedback inhibition plays a critical role in preventing cells from wasting resources and energy

A
59
Q

what does the sigmoidal shape of the curve describes?

A

Allosteric behavior

60
Q

The binding site for ATP on the enzyme molecule is the same as that for CTP, but ATP is rather an INHIBITOR like CTP. When CTP is in short supply in an organism, the ATCase reaction is not inhibited, and the binding of ATP increases the activity of the enzyme still more.

A
61
Q

proposed in 1965; has the advantage of comparative simplicity

A

Concerted model

62
Q

The enzymes has two conformations:

R (relaxed) - binds substrate tightly; active form
T (tight or taut) - binds the substrate less tightly; inactive form

A

Concerted model

63
Q

proposed in 1966; gives a realistic picture of the structure and behavior of proteins

A

Sequential model

64
Q

change in conformation is induced by the fit of the substrate to the enzyme, as per the induced-fit model of substrate binding

represents cooperativity

A

Sequential model

65
Q

binding of the substrate induces a conformational change from the T form to the R form

A

Sequential model

66
Q

most enzyme molecules are in the T (inactive) form in the?

A

Absence of substrate

67
Q

What shifts the equilibrium from the T (inactive) form to the R (active) form

A

The presence of substrate

68
Q

In changing from T to R and vice versa, all subunits change conformation simultaneously; all changes are concerted

A
69
Q

In the concerted model for allosteric behavior,

  • the binding of substrate, inhibitor, or activator to one unit shifts equil. b/w R form of the enzyme (binds substrate strongly), and T form (does not bind substrate strongly)
  • conformational change takes place in all subunits at the same time
A
70
Q

In the sequential model,

  • the binding of the substrate induces the conformational change in one subunit, and the change is subsequently passed along to other subunits
A
71
Q

is one whose activity is modulated by molecules binding at sites other than the active site

A

Allosteric enzymes

72
Q

What is the allosteric enzyme of ATCase?

A

CTP (cytidine triphosphate)

73
Q

end product of the pathway in which ATCase is involved, binds to the enzyme and inhibits its activity through feedback inhibition

A

CTP (cytidine triphosphate)

74
Q

Why is ATCase an allosteric enzyme?

A

because it can be regulated by molecules like CTP, which binds at allosteric sites and inhibits its catalytic activity through a conformational change, thereby controlling the flow of metabolites in pyrimidine biosynthesis

75
Q

Why is chymotrypsin not considered an allosteric enzyme?

A

Because it does not exhibit allosteric regulation, where the binding of a molecule at a site other than the active site affects the enzyme’s activity

76
Q

inactive precursor of an enzyme where cleavage of one or more covalent bonds transforms it into the active enzyme

A

Zymogen

77
Q
  • synthesized and stored in the pancreas
  • a single polypeptide chain of 245 amino acid residues cross-linked by five disulfide (-S-S-) bonds
  • when secreted into the small intestine, the digestive enzyme trypsin cleaves a 15-unit polypeptide from the N-terminal end to give the pi-chymotrypsin; acts on itself to remove two dipeptide fragments, producing alpha-chymotrypsin (fully active)
A

Chymotrypsinogen

78
Q

non-protein chemical compounds/metallic ions that help enzymes perform their catalytic functions

  • inorganic ions (Mg2+ [for DNA polymerase], Fe2+, Zn2+ [for alcohol dehydrogenase]
  • organic molecules (coenzymes are a subset of organic cofactors)

stabilize enzyme structure, participate in the actual catalytic reaction, or assist in substrate binding

A

Cofactors

79
Q

specific type of organic cofactor; typically small organic molecule, that helps enzymes catalyze reactions by acting as carriers for chemical groups or electrons

organic molecules often derived from vitamins

often participate in the reaction by temporarily accepting or donating atoms, ions, or FG

usually regenerate after rxn, allowing them to be used repeatedly

A

Coenzyme

80
Q

All coenzymes are cofactors, but not all cofactors are coenzymes (search more on this)

A
81
Q

Coenzymes often participate directly in the enzymatic reaction, while some cofactors may play more structural or stabilizing roles.

A

BIOCHEM 1 (11 decks)

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