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Biochem B3 > Chp 20 Enzymes > Flashcards

Chp 20 Enzymes Flashcards

1
Q

are globular proteins with a unique three-dimensional shape that recognizes and binds a small group of reacting molecules, called substrates

A

enzymes

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2
Q

have a tertiary structure that includes a region called the active site where one or more small groups of substrates bind to create a chemical reaction.

A

enzymes

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3
Q

have specific amino acid residues within the active site that interact with functional groups of the substrate to form hydrogen bonds, salt bridges, and hydrophobic interactions

A

enzymes

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4
Q

has a rigid substrate binding to a rigid enzyme, much like a key fitting into a lock

A

lock-and-key model

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5
Q

more dynamic model of enzyme action, states that the active site is flexible enough to adapt to the shape of the substrate

A

induced-fit model

The induced-fit model has the substrate and enzyme working together to acquire a geometrical arrangement that lowers the activation energy

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6
Q

Enzymes like lactase have an ____ where the substrate fits for catalysis to occur. The quaternary structure of lactase consists of four subunits. The substrate, lactose (gray), is held in place in the active site by hydrogen bonds with amino acid R groups.

A

active site

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7
Q

Some enzymes show absolute specificity by catalyzing ___ reaction for one specific substrate

A

only one

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8
Q

The combination of an enzyme and a substrate forms a

A

enzyme–substrate (ES) complex

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9
Q

The ES provides an alternative pathway for the reaction with

A

lower activation energy

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10
Q

Within the active site, amino acid R groups catalyze the reaction to form an

A

enzyme–product (EP) complex

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11
Q

oxidoreductases

A

catalyze redox rxns

Oxidases catalyze oxidation of a substrate

Dehydrogenases catalyze removal or addition of two H atoms

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12
Q

Transferase

A

catalyzes the transfer of a functional group between two compounds

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13
Q

Hydrolases

A

catalyzes hydrolysis (adds H20) rxn that split into two producs

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14
Q

Lyases

A

catalyze the addition or removal of a gruop without hydrolyssi

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15
Q

isomerases

A

catalyze the rearrangement of atoms within a substrate

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16
Q

Ligases

A

joiing of two substrates, using ATP

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17
Q

The activity of an enzyme describes how fast an enzyme catalyzes the reaction and is strongly affected by reaction conditions, such as

A

temperature.
pH.
concentration of the enzyme and substrate.

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18
Q

lose activity at ___ temperatures as denaturation occurs

A

high

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19
Q

most active at an ___temperature (usually 37°C in humans).

show little activity at low temperatures.

A

optimum

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20
Q

most active at optimum pH, where proper ___ structure of the protein is maintained

A

tertiary

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21
Q

An increase in enzyme concentration

A

increases the rate of reaction (at constant substrate concentration).
binds more substrate with enzyme

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22
Q

An increase in substrate

concentration

A

increases the rate of reaction (at constant enzyme concentration).
eventually saturates an enzyme with substrate to give maximum activity

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23
Q

type of covalent modification that activates or deactivates an enzyme.

A

Phosphorylation

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24
Q

A kinase activates an inactive enzyme by

A

phosphorylation

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25
Q

A phosphatase activates an inactive enzyme by ___ of a phosphate

A

removal

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26
Q

bind with a regulator molecule at the allosteric site that is different from the active site.
change the shape of the enzyme, which causes a change in the shape of the active site

A

Allosteric enzymes

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27
Q

can be a___ that changes the shape of the active site to allow the substrate to bind more effectively

A

positive regulator

allosteric enzymes

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28
Q

can be a ____ that changes the shape of the active site to prevent the proper binding of the substrate, which decreases the rate of the catalyzed reaction.

A

negative regulator

allosteric enzyme

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29
Q

Enzyme activity can be regulated by allosteric enzymes, feedback control, and

A

covalent modifications

30
Q

In feedback control, when the end product level is high

A

the end product of a series of reactions acts as a negative regulator and binds to the allosteric site.
the substrate cannot bind to the active site, and production of all of the intermediate compounds in the subsequent reaction sequence stops

31
Q

when the level of end product is low

A

the regulator dissociates from the allosteric site on the enzyme, unblocking the active site.
the initial substrate is allowed to bind to the active site again.

32
Q

Enzyme activity is modified by covalent bonds to a group on the polypeptide chain that are formed or broken.
Covalent modification is reversible.

A

Zymogens, or proenzymes, are produced in their inactive form and can be activated at a later time when they are needed

33
Q

Once a zymogen is formed, it is

A

transported to where the active form is needed.

converted to its active form by a covalent modification.

34
Q

different forms of an enzyme that catalyze the same reaction in different cells or tissues of the body.
have quaternary structures with slight variations in the amino acids in the polypeptide subunits

A

Isoenzymes

35
Q

are molecules that cause a loss of catalytic activity.

prevent substrates from fitting into the active sites

A

Inhibitors

can be classified as either reversible inhibitors or irreversible inhibitors.

36
Q

cause a loss of enzyme activity that can be restored.

can act in different ways but do not form covalent bonds with the enzyme

A

Reversible inhibitors

37
Q

Reversible inhibition can be competitive or noncompetitive.

A

Competitive inhibitors compete for the active site.

Noncompetitive inhibitors act on another site that is not the active site.

38
Q

chemical structure and polarity similar to the substrate

A

competitive inhibitor

competes with the substrate for the active site.
has its effect reversed by increasing substrate concentration

39
Q

has a structure that is much different from that of the substrate.
does not compete for the active site.
distorts the shape of the enzyme, which prevents the catalyzing of the substrate at the active site.
cannot have its effect reversed by adding more substrate

A

noncompetitive inhibitor

40
Q

the inhibitor covalently bonds with R groups of an amino acid that may be near the active site

the inhibitor changes the shape of the enzyme, which prevents the substrate from entering the active site

A

irreversible inhibition

41
Q

an active enzyme that consists only of protein

A

simple enzyme

42
Q

Many enzymes are active only when they combine with __ such as metal ions or small molecules

A

cofactors

43
Q

A ___ is a cofactor that is a small organic molecule such as a vitamin

A

coenzyme

44
Q

organic molecules that are essential for normal health and growth.
are required in trace amounts.
need to be obtained from the diet

A

Vitamins

45
Q

Water-soluble vitamins

A

are soluble in aqueous solutions and cannot be stored in the body.
are cofactors for many enzymes.
are excreted in urine each day.
are easily destroyed by heat, oxygen, and ultraviolet light, so care must be taken in food preparation

46
Q

B1 - thiamine

A

beriberi, fatigue, poor appetite, weight loss

47
Q

B2 - riboflavin

A

dermatitis, dry skin, sore tongue, cataracts

48
Q

b3 - niacin

A

pellagra, muscle fatigue, loss of appetite, diarrhea, mouth sores

49
Q

b5 pantothenic acid

A

fatigue, retarded growth, muscle cramps, anemia

50
Q

b6 pyridoxine

A

demratitis, fatigue, anemia, retarded growth

51
Q

b9 folic acid

A

abnormal RBCs, anema, GI issues, loss of hair, growth impairment, depression

52
Q

b12 cobalamin

A

pernicious anemia, malformed RBCs, nerve damage

53
Q

Vit C ascorbic acid

A

scurvy, bleeding gums, weakened connective tissues, slowe healing wounds, anemia

54
Q

Biotin H

A

dermatitis, loss of hair, fatigue, depression

55
Q

Retinol Vit A

A

necessary to avoid blindness, immune system repression, slowed growth

56
Q

Cholecalciferol - VIt D

A

necessary to avoid weakened bones

57
Q

Vit E tocopherol

A

necessary to avoid hemolysis, anemia

58
Q

Vit k menaquinone

A

necessary to avoid prolnged bleeding time & bruising

59
Q

catalyzes the oxidation of a substrate

A

oxidase

oxidoreductase

60
Q

catalyzes removal or addition of two H atomss and utilizes a coenzyme

A

dehydrogenase

oxidoreductase

61
Q

transfer of an amino acid from one substrate to another

A

transaminase

transferase

62
Q

transfer of phosphate gruops from one substrate to another

A

kinase

transferase

63
Q

hydrolysis of peptide bond in proteins

A

proteases

hydrolase

64
Q

hydrolysis of ester bonds in lipids

A

lipases

hydrolase

65
Q

hydrolysis of phosphate ester bonds in nucleic acids

A

nucleases

hydrolase

66
Q

removal of CO2 from a substrate

A

decarboxylase

lyase

67
Q

removal of NH3 from a substrate

A

deaminases

lyase

68
Q

removal of H20 from a substrate

A

dehydratases

lyase

69
Q

catalyze the addition of H20 to a substrate

A

hydratases

lyase

70
Q

rearrangment of carbohydrates

A

epimerases

type of isomerase

71
Q

formation of a bond between two substrates utilizing ATP

A

synthestases

ligases

72
Q

formaiton of a bond between CO2 and a substrate using ATP

A

carboxylases

ligase

Biochem B3 (5 decks)

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