CHAPTER 7: Behavior of Proteins (Enzymes, Mechanisms, and Control)

Question 1

a substance that modifies the behavior of an allosteric
enzyme by binding to it.

Answer 1

Allosteric Effector

Question 2

Substances change the enzyme’s activity by altering the conformation(s) Of?

Answer 2

of its 4º structure

Question 3

exhibit cooperative effects caused by subtle
changes in quaternary structure.

Answer 3

ATCase and Hemoglobin

Question 4

A process by which the final product of a series of reactions inhibits the first
reaction in the series.

Answer 4

FEEDBACK INHIBITION

Question 5

what is used for allosteric anzymes? hyperbola or sigmoidal

Answer 5

sigmoidal. Kapg sa ATCase ung part n si CTP ininhibit ung process, its hyperbola na ulit

Question 6

six protein subunits organized into two trimers.

Answer 6

Catalytic subunit

Question 7

six protein subunits organized into three dimers.

Answer 7

Regulatory subunit

Question 8

Catalytic and regulatory subunit can be spearated by

Answer 8

p-
hydroxymercuribenzoate

Question 9

an enzyme for which inhibitors or activators alter the substrate
concentration that yields one-half Vmax.

Answer 9

K system

Question 10

an enzyme in which the presence of an inhibitor or activator
changes the maximal velocity of the enzyme but not the substrate level that
yields one-half Vmax

Answer 10

V system

Question 11

In K system, instead of Vmax ano gamit

Answer 11

V0.5

Question 12

substrate, inhibitor, or activator that binds to an
allosteric enzyme and affects its activity.

Answer 12

Allosteric Effector

Question 13

allosteric effects that occur when several
identical molecules are bound to a protein.

Give example

Answer 13

homotropic effects

binding of aspartate to ATCase

Question 14

allosteric effects that occur when different
substances are bound to a protein

Example

Answer 14

heterotropic effects

CTP inhibiting ATCase and ATP activating it

Question 15

enzyme that catalyzes transfer of a phosphate group to some substrate

Answer 15

kinaseee

Question 16

Differentiate concerted and sequential binding

Answer 16

Sa concerted it may be active(R) or inactive form(T). Entire protein structure changes regardless of how many molecules are bound

Sa sequential, only the one part of an enzyme changes. it suggests that subunits change states one at a time, progressively increasing their affinity for the substrate.

Question 17

refers to a situation in enzyme or protein binding where the binding of a substrate or ligand to one active site reduces the likelihood that additional substrate molecules will bind to other active sites on the same enzyme or protein.

Answer 17

negative cooperativity

Question 18

enzyme for phosphorylation

Answer 18

protein kinase, usually binds to serine, threonine, tyrosine

Question 19

enzyme for dephosphorylation

Answer 19

protein phosphotase

Question 20

What are zymogens

Answer 20

an inactive protein that can be activated by specific hydrolysis of peptide bonds

Question 21

Inactive cursos of trypsin and chymotrypsin, where is it formed?

Answer 21

trypsinogen and chymotrypsinogen in the pancreas.

Question 22

chymotrypsinogen consist of

Answer 22

single polypeptide chain 245 residues long with 5 disulfide bonds

Question 23

Explain the activation of chymotrypsin

Answer 23

Chymotrypsinogen(primary) is relased to the stomach, then the trypsin cleaves the peptide bonds between arginiine 15 and isoleucine 16 forming π- chymotrypsin then Ser 14-Arg 15- and THr 147- Asn 148 is removed producing alpha- chymotrypsin (tertiary)

Question 24

consists of 3 polypeptide chains joined by 2 of the five
original disulfide bonds.

Answer 24

alpha-chymotrypsin

Question 25

examples of serine protease.

Answer 25

chymotrypsin, thrombin, trypsin

Question 26

critical for activation of chymotrypsin.

Answer 26

histidine 57

Question 27

Can be chemically labeled by N-tosylamido-L-phenylethyl chloromethyl ketone (TPCK

Answer 27

histidne 57

Question 28

required for the activity of chymotrypsin. o Must be close to each other on the active site.

Answer 28

Hisitidine 57 and Serine 195 (and aspartate 102)

Question 29

common nucleophiles

Answer 29

oxygen or serine, threonine, tyrosine... they attack the carbon of the carbonyl group

Question 30

show the definite spatial relationship among active site residues. o Folding of the chymotrypsin backbone, mostly in an antiparallel pleated sheet array, positions the essential amino acid residues around the active-site pocket.

Answer 30

X-Ray Crystallography Results

Question 31

True or false: SN1 reaction tendds to lead to loss of stereospecificty

Answer 31

true

Question 32

What kind of reaction is chymotrypsin nucleophilic attacks?

Answer 32

SN2

Question 33

Lewis Acids are

Answer 33

electrophile: Mn2+, Mg2+, Zn2+

Question 34

requires Zn2+ for enzyme activity

Answer 34

Carboxypeptidase A: activates the carbonyl group for nucleophilic acyl substitution. o Complexed to the imidazole side chains of histidine 69 and 196 and the carboxylate side chains of glutamate 72.

Question 35

catalyzes the reaction of one unique substrate to a particular product.

Answer 35

Absolute Specificity

Question 36

catalyzes the reaction of structurally related substrates to give structurally related products.

Answer 36

Relative Specificity

Question 37

catalyzes a reaction in which one stereoisomer is reacted or formed in preference to all others that might react or form. o Example: hydration of a cis alkene (not trans isomer) to give an R alcohol (not the S alcohol)

Answer 37

Stereospecificity

Question 38

antibodies produced against a transition-state analog and have catalytic activity similar to a naturally occurring enzyme.

Answer 38

abyzymes

Question 39

Nonprotein substances that participate in enzymatic reactions are regenerated at the end of the reaction

Answer 39

conezymes

Question 40

Coenzyme in many oxidation-reduction reactions. * Structure: consists of a nicotinamide ring, adenine ring, and two sugar- phosphate groups linked together

Answer 40

NICOTINAMIDE ADENINE DINUCLEOTIDE (NAD+)

Question 41

in the compound nicotinamide adenine dinucletide, where do redox happens?

Answer 41

nicotinamide ring- where reduction-oxidation occurs.

Question 42

group of chemically related compounds—pyridoxal, pyridoxamine, and pyridoxine—and their phosphorylated forms. Vitamin B6

Answer 42

Vitamin B6

Question 43

Active form of Vitamin B6

Answer 43

Pyridoxal phosphate/pyridoxamine phosphate