Control of Enzyme Activity—Introduction to Metabolism

Question 1

What is metabolism ?

Answer 1

highly integrated network of chemical reactions

Question 2

catabolism

Answer 2

catabolism : fuel to energy

Question 3

anabolism

Answer 3

anabolism: energy + simple precursor to complex molecule

Question 4

Ways of Regulating Metabolic Processes (Pathways)?

Answer 4

contolling amount of enzymes,catalytic activity and compartmentalization of substrates

Question 5

5 Ways of Controlling Enzyme Activity

Answer 5

Amount of enzyme in the cell
Allosteric control of enzymes 
Through existence of ISOZYMES
Reversible covalent modification
Proteolytic activation

Question 6

allosteric enzymes? (4 things it does)

Answer 6

exhibit cooperativity in responses to substrate
obey the Monod-Wyman-Changeux (MWC) model
Often serve as control points in pathways
Subject to feedback inhibition

Question 7

Monod-Wyman-Changeux (MWC) model of allosteric behavior

Answer 7

Equilibrium between “T” and “R” states exists; allosteric effectors shift equilibrium

Question 8

what Catalyzes first committed step of pyrimidine synthesis (in E. coli):

Answer 8

ATCase

Question 9

in the 1st committed step of pyrimidine synthesis, what compound controls allosteric inhibition and activation? (2 separate things)

Answer 9

CTP inhibit

ATP activate

Question 10

two subunits seen in Aspartate Transcarbamoylase, ATCase

Answer 10

C (catalytic site)and

R (regulatory site)

Question 11

Which site does ATP and CTP bind too

Answer 11

R site

Question 12

what is a Competitive inhibitor of both substrates, aspartate and carbamoyl phosphate?

Answer 12

PALA -N-(Phosphonacetyl)–L-Aspartate

Question 13

Upon binding PALA will place ATCase in the __ state ?

Answer 13

R

Question 14

in absence of substrate aspartate, ATCase will exist in what kind of state ?

Answer 14

Low activity T state

Question 15

in the presence of CTP ATCase will exist in what kind of state ?

Answer 15

Low activity T state

Question 16

Higher levels of aspartate increasingly shift equilibrium from

Answer 16

T” to “R”

Question 17

Inhibitor CTP shifts equilibrium toward __ state ?

Answer 17

T

Question 18

Activator ATP shifts equilibrium toward __ state?

Answer 18

R

Question 19

Why ATP would activate ATCase?

why is ATP used in this reaction

Answer 19

Pyrimidine-purine balance needed for mRNA or DNA synthesis

Question 20

Isozymes are Homologous enzymes that catalyze same reaction BUT

Answer 20

Are encoded by different genes
Hve similar AAs
Are often expressed in a tissue-specific or developmental stage-specific manner

Question 21

An example of an isozyme is ?

Answer 21

LDH

Question 22

Combitations of teramers possible by LDH

Answer 22

M4, M3H, M2H2, MH3, H4

Question 23

6 Different Post-Translational Covalent Modification of Enzymes/ Proteins?

Answer 23

phosphorylation, acetylation, carboxylation, ubiquitylation, lipidation, glycosylation

Question 24

in phosphorylation what catalyzes the attachment and removal of phosphate?

Answer 24

protein kinase

removal- protein phosphatase

Question 25

In phosphorylatipn what different residues do phosphates attach too ?

Answer 25

serine, threonine, or tyrosine

Question 26

Acetylation activates __?

Answer 26

gene transcription / opens up DNA

Question 27

Ubiquitylation In cytoplasm targets proteins for destruction via the

Answer 27

proteaosome

Question 28

In the nucleus this type of modificationcan alter properties of histones and other proteins involved in gene expression

Answer 28

ubiquitylation

Question 29

which covalent Modification allows the clotting factors to chelate calcium and adhere to vessel wall near site of injury ?

Answer 29

carboxylation

Question 30

Allows the subunits to move along the cytoplasmic face of membrane; speeds up their interaction with downstream effectors

Answer 30

lipidation

Question 31

Gs(alpha) with adenylyl cyclase is seen in this type of covalent modification

Answer 31

lipidation

Question 32

Attachment of carbohydrate groups, including modified sugars (GlcNAc) and oligosaccharide groups is seen in this type of covalent modification ?

Answer 32

glycosylation

Question 33

Which residues (AA) does glycosylation attach to ?

Answer 33

Covalent attachment is to serine, threonine or asparagine residues

Question 34

in glycosylation, modification is directed to (3 things ) ?

Answer 34

Modification is to extracellular domain of transmembrane proteins, or secreted proteins (e.g., EPO), or proteins destined for lysosome

Question 35

chelate ?

Answer 35

compound containing a ligand bonded to a central metal atom at 2 more points? "grab and bond to "

Question 36

phosphorylation and glycosyation are the only reversible reactions in Post-Translational Covalent Modification of Enzymes/ Proteins?

Answer 36

Falce : phosphoylation AND aceylation

Question 37

ATP provides energy by simple hydrolysis. T/F?

Answer 37

False. ATP provides energy by group transfer.

Question 38

what is used to lower ADP levels during periods of intense demand for ATP

Answer 38

Adenylate kinase

Question 39

reasons why there is a large (-) delta G of hydrolysis of ATP?

Answer 39

1. More resonance forms 2. less bond strain (repulsion) in ADP 3. Greater degree of solvation (hydration) in products

Question 40

Coupled reactions

Answer 40

refers to coupling unfavorable and favorable reactions to drive reaction forward

Question 41

coupled reaction examples

Answer 41

1. Unactivated vs activated conformations of a motor protein 2. hydrolysis of ATP 3. ATPase

Question 42

what compound has 2 phosphoanhydride bonds that, when hydrolyzed, yield a lot of free energy

Answer 42

ATP

Question 43

Phoshpoanhydride bond?

Answer 43

links a ribose sugar and. three phosphate groups

Question 44

High energy compound thar rapidly synthesizes ATP when low in the muscle

Answer 44

creatine phosphate

Question 45

In exercise __ ttansfers phosphryl group to ADP to generate ATP

Answer 45

Creatine phosphate

Question 46

In enol phosphates such as phosphoenolpyruvate what will give the product more stabiulty than reactant

Answer 46

the ability to tautomerize

Question 47

tautomerism

Answer 47

isomers of a compound which differ only in the position of the protons and electrons. usually seen as a PROTON TRANSFER

Question 48

ATP generating pathways are __ by high energy charge

Answer 48

inhibited : seen in catabolic

Question 49

ATP utilizing pathways are __ by high energy charge

Answer 49

activated :seen in anabolic

Question 50

activated carriers of electrons for fuel oxidation

Answer 50

NAD+, NADH and FAD

Question 51

activated carriers of elctons for reductive biosynthesis

Answer 51

NADP+, NADPH .

Question 52

[NADP+]/[NADPH] is kept low or high ?

Answer 52

low so hydride trasfer favors [NADPH]

Question 53

[NAD+]/[NADH] is kept low or high ?

Answer 53

HIGH low so hydride trasfer favors [NAD+]

Question 54

this type of covalent modification is seen in the alpha and beta/gamma subunits of heterotrimeric G-proteins

Answer 54

lipidation