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Biochemistry > Control of Enzyme Activity—Introduction to Metabolism > Flashcards

Control of Enzyme Activity—Introduction to Metabolism Flashcards

1
Q

What is metabolism ?

A

highly integrated network of chemical reactions

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2
Q

catabolism

A

catabolism : fuel to energy

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3
Q

anabolism

A

anabolism: energy + simple precursor to complex molecule

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4
Q

Ways of Regulating Metabolic Processes (Pathways)?

A

contolling amount of enzymes,catalytic activity and compartmentalization of substrates

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5
Q

5 Ways of Controlling Enzyme Activity

A 
Amount of enzyme in the cell
Allosteric control of enzymes 
Through existence of ISOZYMES
Reversible covalent modification
Proteolytic activation
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6
Q

allosteric enzymes? (4 things it does)

A

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

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7
Q

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

A

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

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8
Q

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

A

ATCase

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9
Q

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

A

CTP inhibit

ATP activate

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10
Q

two subunits seen in Aspartate Transcarbamoylase, ATCase

A

C (catalytic site)and

R (regulatory site)

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11
Q

Which site does ATP and CTP bind too

A

R site

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12
Q

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

A

PALA -N-(Phosphonacetyl)–L-Aspartate

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13
Q

Upon binding PALA will place ATCase in the __ state ?

A

R

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14
Q

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

A

Low activity T state

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15
Q

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

A

Low activity T state

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16
Q

Higher levels of aspartate increasingly shift equilibrium from

A

T” to “R”

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17
Q

Inhibitor CTP shifts equilibrium toward __ state ?

A

T

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18
Q

Activator ATP shifts equilibrium toward __ state?

A

R

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19
Q

Why ATP would activate ATCase?

why is ATP used in this reaction

A

Pyrimidine-purine balance needed for mRNA or DNA synthesis

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20
Q

Isozymes are Homologous enzymes that catalyze same reaction BUT

A

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

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21
Q

An example of an isozyme is ?

A

LDH

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22
Q

Combitations of teramers possible by LDH

A

M4, M3H, M2H2, MH3, H4

23
Q

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

A

phosphorylation, acetylation, carboxylation, ubiquitylation, lipidation, glycosylation

24
Q

in phosphorylation what catalyzes the attachment and removal of phosphate?

A

protein kinase

removal- protein phosphatase

25
Q

In phosphorylatipn what different residues do phosphates attach too ?

A

serine, threonine, or tyrosine

26
Q

Acetylation activates __?

A

gene transcription / opens up DNA

27
Q

Ubiquitylation In cytoplasm targets proteins for destruction via the

A

proteaosome

28
Q

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

A

ubiquitylation

29
Q

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

A

carboxylation

30
Q

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

A

lipidation

31
Q

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

A

lipidation

32
Q

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

A

glycosylation

33
Q

Which residues (AA) does glycosylation attach to ?

A

Covalent attachment is to serine, threonine or asparagine residues

34
Q

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

A

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

35
Q

chelate ?

A

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

36
Q

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

A

Falce : phosphoylation AND aceylation

37
Q

ATP provides energy by simple hydrolysis. T/F?

A

False. ATP provides energy by group transfer.

38
Q

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

A

Adenylate kinase

39
Q

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

A
  1. More resonance forms
  2. less bond strain (repulsion) in ADP
  3. Greater degree of solvation (hydration) in products
40
Q

Coupled reactions

A

refers to coupling unfavorable and favorable reactions to drive reaction forward

41
Q

coupled reaction examples

A
  1. Unactivated vs activated conformations of a motor protein
  2. hydrolysis of ATP
  3. ATPase
42
Q

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

A

ATP

43
Q

Phoshpoanhydride bond?

A

links a ribose sugar and. three phosphate groups

44
Q

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

A

creatine phosphate

45
Q

In exercise __ ttansfers phosphryl group to ADP to generate ATP

A

Creatine phosphate

46
Q

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

A

the ability to tautomerize

47
Q

tautomerism

A

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

48
Q

ATP generating pathways are __ by high energy charge

A

inhibited : seen in catabolic

49
Q

ATP utilizing pathways are __ by high energy charge

A

activated :seen in anabolic

50
Q

activated carriers of electrons for fuel oxidation

A

NAD+, NADH and FAD

51
Q

activated carriers of elctons for reductive biosynthesis

A

NADP+, NADPH .

52
Q

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

A

low so hydride trasfer favors [NADPH]

53
Q

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

A

HIGH low so hydride trasfer favors [NAD+]

54
Q

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

A

lipidation

Biochemistry (9 decks)

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