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Biochem > Enzyme Catalysis > Flashcards

Enzyme Catalysis Flashcards

1
Q

Enzymes are biological catalysts. Describe what a catalyst does

A

increases rate of reaction but does not effect the equilibrium constant

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2
Q

A catalyst decreases activation energy. True or false?

A

true

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3
Q

Does an enzyme effect the free energy of a reaction?

A

no

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4
Q

Reaction rates of enzymatically catalyzed reactions are generally how much greater than non-catalyzed reactions? non-enzymatically catalyzed reactions?

A

10^6 - 10^12; 10^3

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5
Q

Enzymatic reactions have milder reaction conditions. Describe some of these conditions

A

occur at atmospheric pressure, neutral pH, and temperatures less than 100 degrees celsius

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6
Q

Enzymatic reactions have tremendous reaction specificity that results in what?

A

very rarely occurring side products

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7
Q

True or false?

Enzyme activity can vary in response to biological molecules other than the enzyme’s substrates or products

A

true

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8
Q

What is a unit of enzyme activity?

A

the amount of substrate converted to product in a given amount of time

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9
Q

What is a specific activity of an enzyme?

A

the number of units per mg protein

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10
Q

Most human enzymes have a temperature optimum of about ___ degrees celsius

A

37

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11
Q

Pepsin is an enzyme in the stomach and has a pH optimum of about ___. Trypsin is an enzyme active in the small intestine and has a pH optimum of about ___

A

2; 8

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12
Q

What type of reaction does an oxidoreductase enzyme catalyze? give some examples of oxidoreductase enzymes

A

oxidation-reduction reactions; dehydrogenases, oxidases, reductases, peroxidases, catalase, oxygenase, hydroxylase

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13
Q

What type of reaction does a transferase enzyme catalyze? give some examples of transferase enzymes

A

catalyze transfer of a group such as glycosyl, methyl, or phosphoryl; transaldolase, transketolase, acyl transferase, kinases, phosphomutases

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14
Q

What type of reaction do hydrolases catalyze? give some examples of hydrolase enzymes

A

catalyze hydrolytic cleavage of C-C, C-O, C-N, and other bonds; esterase’s, glycosides, peptidases, phosphotases, etc

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15
Q

What type of reaction do lyases catalyze? give some examples of lyase enzymes

A

catalyze cleavage of C-C, C-O, C-N, and other bonds by atom elimination, leaving double bonds; decarboxylases, aldolases, hydratases, dehydratases, synthases

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16
Q

What type of reaction do isomerases catalyze? give some examples of isomerase enzymes

A

catalyze geometric or structural changes within a molecule; racemases, epimerases, isomerases, some mutases

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17
Q

What type of reaction do ligases catalyze? give some examples of ligase enzymes

A

catalyze the joining together of two molecules coupled to the hydrolysis of ATP; synthetases and carboxylases

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18
Q

Define active site

A

a specific region on the enzyme where the reaction occurs

19
Q

The ___ of the enzyme is critical for the appropriate structure of the active site

A

structure

note: lock and key - enzyme has to fit

20
Q

Changes in the enzyme structure (due to AA composition) may or may not have major effects on the activity of the enzyme. True or false?

A

true

21
Q

In regards to catalysis by proximity, in order for molecules to react, they must come within ____ ____ distance of each other

A

bond forming

22
Q

In regards to catalysis by proximity, the active site of an enzyme binds substrates creating a ___ local concentration

A

high

23
Q

In regards to catalysis by proximity, the substrates are also bound in a ___ ___ conducive to reaction

A

specific orientation

24
Q

In regards to acid-base catalysis, ____ functional groups of AA side chains may participate in catalysis by acting as acids and/or bases

A

ionizable

25
Q

In regards to catalysis by strain, enzymes which catalyze reactions which break bonds may bind substrates in what type of manner?

A

in such a way to destabilize the bond to be broken

26
Q

In regards to covalent catalysis, a ___ bond is established between substrate and enzyme

A

covalent

27
Q

In regards to covalent catalysis, the covalently modified enzyme essentially then becomes a ___ for the reaction

A

substrate

28
Q

In regards to covalent catalysis, the reaction of covalently modified enzyme to product is more ___ ____ than the reaction of substrate to product

A

energetically favorable

29
Q

What are cofactors, coenzymes, and prosthetic groups? (in general as a group)

A

small, non-protein molecules and metal ions which participate directly in the enzymatic process

30
Q

Many cofactors, coenzymes, and prosthetic groups are derived from what?

A

vitamins

31
Q

Prosthetic groups are tightly and stably incorporated into the protein, sometimes by ___ bonds

A

covalent

32
Q

metal ions are the most common prosthetic groups. give some examples

A

Co, Cu, Mg, Mn, and Zn

33
Q

enzymes containing a metal prosthetic group are called _____

A

metalloenzymes

34
Q

Pyroxial phosphate is a prosthetic group derived from what?

A

vitamin pyrodoxine, B6

35
Q

Thiamine pyrophosphate is a prosthetic group derived from what?

A

thiamine, B1

36
Q

FMN and FAD are prosthetic groups derived from what?

A

riboflavin, vitamin B2

37
Q

Cofactors bind _____ to either the substrate or the enzyme but are nonetheless required for activity

A

transiently

38
Q

What is the most common cofactor?

A

Mg2+

note: it is required for enzymes which involve ATP

39
Q

Coenzymes serve as “___”, accepting a group from one reaction and supplying the group in other reactions

A

shuttles

40
Q

Coenzyme A transfers what?

A

acyl groups

41
Q

Folates transfer what?

A

one carbon groups

42
Q

Isoenzymes are physically distinct enzymes, meaning they are different proteins with different AA sequences which catalyze what?

A

the same reaction

43
Q

What are some of the different properties between isoenzymes?

A

kinetic differences (substrate affinities), differences in activity regulation

44
Q

Isoenzymes may be differentially expressed by different tissues. Give an example

A

the heart isoenzymes of creatine kinase may be distinguished form the skeletal muscle isoenzymes of creatine kinase

Biochem (38 decks)

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