Bio Chem Quiz 5

Front 1

Oxidoreductases

Back 1

transfer of electrons (hydride ions or H atoms)

Front 2

Transferases

Back 2

Group Transfer reactions

Front 3

Hydrolases

Back 3

Hydrolysis reactions (transfer of functional groups to water)

Front 4

Lyases

Back 4

addition of groups to double bonds, or formation of double bonds by removal of groups

Front 5

ligases

Back 5

formation of C-C, C-S, C-O, and C-N bonds by condensation reaction coupled to cleavage of ATP or similar cofactors

Front 6

The power of an enzyme catalyst derives from what two properties

Back 6

1-specificity of substrate binding and optimal arrangement of chemical groups involved in catalysis

Front 7

6 major enzyme mechanisms

Back 7

1-acid base
2-covalent
3-metal ion
4-electrostatic
5-proximity and orientation effects
6- preferential binding of the transition state complex

Front 8

what mechanism is used to label the enzyme mechanism

Back 8

the mechanism that dominates the rate determining step of the reaction

Front 9

General acid catalysis:

Back 9

transition state (TS) stabilized by H+ transfer from an acid to the substrate

Front 10

General base Catalysis:

Back 10

TS is lowered by H+ transfer from the substrate to a base

Front 11

True or false
A concerted general acid-base catalyzed reaction involves both processes simultaneously

Back 11

True

Front 12

General amino acids that act as acid-base catalysts?

Back 12

Asp, Glu, His, Cys, Tyr, Lys, and Arg

*whether amino acid acts as acid or base is dependent on its form (protonated or deprotonated).

Front 13

molecule that can also act as an acid-base in enzyme catalyzed reactions?

Back 13

Water (called "specific" acid-base catalysis)

Front 14

what can determine the acid or base characteristics of amino acid side chains in enzymes?

Back 14

the local environment within the protein.

Front 15

What type of enzymatic reaction does Chymotrypsin follow?

Back 15

Acid-Base

Front 16

Types of reaction catalyzed primarily through acid-base catalysis?

Back 16

1-hydrolysis of peptides and esters
2-transfer of phosphate groups
3-Tautomerizations
4-addition of carbonyls

Front 17

Which of the following is true about acid base catalysis?
A. it requires the ions of water
B. Amino acid side chains on enzymes can act as proton donors or acceptors
C. often involves covalent bonds formed between a metal ion and the substrate
D. it involves a transient covalent bond between the enzyme and the substrate

Back 17

B. Amino acid side chains on enzymes can act as proton donors or acceptors

Front 18

In covalent catalysis rate acceleration is achieved through...?

Back 18

Formation of a transient covalent bond between substrate and enzyme

Front 19

What does the formation of a transient covalent bond do for a enzymatic reaction?

Back 19

It directs the path of the reaction by activating the substrate for subsequent reaction.

Front 20

The catalytic group involved in covalent catalysis must have what properties?

Back 20

Must be a good nucleophile (to form the covalent bond)

and must be a good leaving group so as to be able to break the bond

Front 21

what type of functional groups make good covalent catalysts?

Back 21

Highly polar groups

Front 22

name some AA's that make good covalent catalysts?

Back 22

Lys, His, Cys, Asp, Glu, and Ser

Front 23

Primary reaction catalyzed through covalent catalysis?

Back 23

1-Decarboxylations
2-Amino Transfers
3-Proteolysis

Front 24

Metalloenzymes?

Back 24

enzymes that contain tightly bound metals, most usually transition metals such as Fe, Cu, Zn

Front 25

Metal activated enzymes?

Back 25

Enzymes that are activated by loosely bound metals, most usually alkali or alkaline earth metals, such as... Na, Ca, Mg. These metals often come associated with a substrate.

Front 26

3 major ways metals participate in catalysis

Back 26

1- binding to substrates to orient them properly for reaction(metal activated enzymes)
2-Meiating redox reaction by donating/accepting electrons (metalloenzymes)
3- electrostatically stabilizing or shielding negative charges (metal-activated enzymes)

Front 27

Electrostatic catalysis

Back 27

this is the stabilization of enzyme bound intermediates that develop a charge

Front 28

"oxyanion hole"

Back 28

this involves the stabilization of a negatively charge covalent catalytic intermediate by a positively charge amino acid, or by hydrogens containing a partial positive charge due to their covalent bonding to an electronegative atom (i.e. Hydogen bonding).

Front 29

what must happen for electrostatic catalysis?

Back 29

in order to react two substrates must be close in proximity to each other, and with correct orientation

Front 30

Proteases

Back 30

catalyze the hydrolysis of polypeptide backbones to yield smaller peptides

Front 31

where does trypsin cleave

Back 31

Arg, and Lys on the C-terminal side

Front 32

where does chymotrypsin cleave

Back 32

Phe, Tyr, Trp

Front 33

where does elastase cleave

Back 33

Cleaves smaller non-polar AA's (A,G,S,V

Front 34

serine proteases have what particular reactive AA that is essential for catalytic activity?

Back 34

serine

Front 35

what three residues form a hydrogen bonded catalytic triad in chymotrypsin

Back 35

Ser 195 and His57, also Asp 102 which is buried in a solvent inaccessible pocket

Front 36

In an enzymatic pathway the first enzyme in a sequence is referred to as..?

Back 36

the regulatory enzyme

Front 37

when enzymes are regulated through a change in their specific activity, with no change in their abundance.... this has what type of response?

Back 37

a fast response

Front 38

When enzymes are regulated through their abundance with no change in activity... this is has what type of response?

Back 38

a slower, longer lasting response

Front 39

changes in specific activity involve what type of regulation?

Back 39

allosteric regulation, covalent modification and zymogen activation

Front 40

changes in abundance levels of enzymes are controlled by....?

Back 40

gene regulation, protein synthesis, and degradation

Front 41

6 types of protein regulation?

Back 41

1-allosteric reg (feedback inhibition)
2-covalent modification (e.g. phosphorolation)
3- cellular compartmentalization
4- zymogen activation (zymogens are inactive precursors forms of enzymes
5- protein synthesis/gene regulation (turning on/off making of specific proteins)
6-protein degradation

Front 42

describe allosteric enzyme regulation

Back 42

enzymes that have both active site and a separate site for allosteric activators which enhance the enzymes catalytic activity

Front 43

affect the Vmax and/or the Km (substrate binding)....?

Back 43

Allosteric activators

Front 44

What affect do allosteric activators have on Vmax/and or Km

Back 44

the lower the Km (substrate binding affinity, and they increase the Vmax

Front 45

Molecules that decrease the catalytic activity are known as?

Back 45

allosteric inhibitors

Front 46

allosteric inhibitors do what to the Km and/or Vmax

Back 46

raise the Km, and Decrease the Vmax

Front 47

Describe feedback inhibition

Back 47

when a multi enzyme pathway produces an excess of the final product, that end product acts as a inhibitor by binding to the regulatory enzyme.

Front 48

where does the final product bind in feedback inhibition?

Back 48

it binds to a allosteric site at the regulatory enzyme (also known as the regulatory site).

Front 49

In catabolic pathways ATP acts as what?

Back 49

an inhibitor

Front 50

in catabolic pathways ADP and AMP act as what?

Back 50

activators (allosteric)

Front 51

in anabolic pathways ATP acts as what?

Back 51

activator (allosteric)

Front 52

In anabolic pathways ADP and AMP act as...?

Back 52

Inhibitors