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biochem > ch 15 part 1 > Flashcards

ch 15 part 1 Flashcards

1
Q

do allosteric enzymes follow michaelis menten kinetics? yes/no and why/why not

A

allosteric enzymes do not follow the michaelis menten kinetics (exponential shape), because while other enzymes have a single polypeptide chain, allosteric enzymes have multiple polypeptide chains making their kinetics graph shape be a S shape.

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2
Q

what is a allosteric effector

A

a molecule that binds to the site of an allosteric enzyme, causing a change in configuration in enzyme activity.

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3
Q

what is a positive effector

A

increases enzyme activity

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4
Q

what is a negative effector

A

decreases enzyme activity

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5
Q

effectors can be what two things

A

homotropic or heterotropic

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6
Q

what is a homotropic effector

A

binds to the active site of the enzyme

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7
Q

what is a heterotropic effector

A

binds at a site other than the active site

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8
Q

what is one thing you need for enzyme cooperativity

A

you need to have multiple polypeptide chains

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9
Q

what is enzyme cooperativity

A

when the shape of one subunit of an enzyme consisting of several subunits is altered by the substrate

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10
Q

what can the binding of the substrate cause to enzyme cooperativity

A

the change can make you better at your job (positive cooperativity) or bad at your job (negative cooperativity).

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11
Q

positive cooperativity

A

when the shape of one subunit of an enzyme gets changed and this causes other subunits of the enzyme to change as well, making the job of the enzyme more efficient

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12
Q

negative cooperativity

A

when the shape of one subunit of an enzyme gets changed and this causes other subunits of the enzyme to change as well, making the job of the enzyme less efficient

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13
Q

what is feedback regulation

A

A process by which the product of a metabolic pathway influences its own production by controlling the amount and/or activity of one or more enzymes involved in the pathway.

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14
Q

what is positive feedback and why does it happen

A

a process by which the product of a metabolic pathway influences its own production by allowing the pathway to continue by binding to one enzyme that is part of the pathway. this can occur when there is not enough of the product from its pathway so it uses its own product to produce more

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15
Q

what is negative feedback

A

a process by which the product of a metabolic pathway influences its own production by blocking the process (by binding to an enzyme part of the pathway inhibiting the enzyme from doing its job) to diminish the amount of product in the body. this occurs when their is too much product in the body so it gives the body enough time to absorb it so once there isn’t enough, the product of the pathway restarts the process of making more.

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16
Q

what is phosphorylation/dephosphorylation?

A

a reversible mechanism to activate/deactivate an enzyme that attaches a phosphate group or removes it FROM ANY ANIMO ACID THAT CONTAINS AN OH GROUP LIKE SER, THR, and TYR

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17
Q

phosphorylation is what kind of reaction

A

condensation reaction that is reversible

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18
Q

dephosphorylation is what kind of reaction

A

hydrolysis that is reversible

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19
Q

what amino acids can go through phosphorylation/dephosphorylation?

A

SER, THR, TYR

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20
Q

what is a protein kinase

A

enzyme that attaches phosphorous group to SER, THR, and TYR

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21
Q

what is a phosphatase

A

enzyme that removes a phosphorous group from SER, THR, TYR

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22
Q

how are protein kinases and phosphatases different from zymogens

A

they are reversible mechanisms of action (reversible covalent bond) while zymogens are irreversible which creates an irreversible covalent bond

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23
Q

what are zymogens

A

inactive precursors of an enzyme, when turned into the active enzyme, this reaction is irreversible.

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24
Q

why could our body create zymogens

A

often times, our hormones are made in different locations from where theyre used like our digestive enzymes. our digestive enzymes are made in our pancreas and we know that our digestive enzyme’s are very acidic and strong and could burn our pancreas if created into the active form there. this way, our precursors are able to travel to our stomach without damaging other organs

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25
Q

what are some examples of zymogens in our bodies

A

proinsulin to insulin, prodigestive enzymes to active digestive enzymes, prothrombin to thrombim

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26
Q

go through the amplification cascade of our pancreatic proteases

A
  1. enteropeptidase creates trypsinogen 2. trypsinogen (inactive) creates trypsin (active) 3. trypsin (active) creates four different zymogens chymotrypsinogen, proelastase, procarboxypeptidase, and prolipase 4. these four zymogens creates chymotrypsin from chymotrypsinogen, elastase from proelastase, carboxypeptidase from procarboxypeptidase, and lipase from prolipase
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27
Q

what is the zymogen that gives to thrombin

A

prothrombin

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28
Q

what is the zymogen that gives to fibrin

A

fibrinogen

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29
Q

what is the zymogen that gives to lipase

A

prolipase

30
Q

what is the zymogen that gives to carboxypeptidase

A

procarboxypeptidase

31
Q

what is the zymogen that gives to chymotrypsin

A

chymotrypsinogen

32
Q

what is the zymogen that gives to elastase

A

proelastase

33
Q

what is the enzyme that comes from trypsinogen

A

trypsin

34
Q

what is the enzyme that comes from proelastase

A

elastase

35
Q

what is the enzyme that comes from chymotrypsinogen

A

chymotrypsin

36
Q

what is the enzyme that comes from procarboxypeptidase

A

carboxypeptidase

37
Q

what is the enzyme that comes from fibrinogen

A

fibrin

38
Q

what is the enzyme that comes from prothrombin

A

thrombin

39
Q

is this big substitution? His to ala

A

yes because you go from positive charge to neutral

40
Q

A—(enzyme #1)–>B—(enzyme #2)–>C—(enzyme #3)–>D—(enzyme #4)
What does it mean if product D blocks its own synthesis

A

its an inhibitor which means this is negative feedback loop

41
Q

A—(enzyme #1)–>B—(enzyme #2)–>C—(enzyme #3)–>D—(enzyme #4) What does it mean if product D accelerates its own synthesis

A

its an activator which means this is a positive feedback loop

42
Q

what does big Km (K0.5) mean

A

low affinity, means alot of substrate present, lower enzymatic efficiency

43
Q

what does low Km (K0.5) mean

A

high affinity, means limited substrate, higher enzymatic efficiency

44
Q

in the ATCase pathway what enzyme is an activator and which one is an inhibitor

A

CTP is an inhibitor and ATP is an activator

45
Q

What is Aspartate Carbamoyl Transferase, what process is it part of, and what step does this occur

A

an enzyme that adds a carbamoyl group to aspartate. this is the first step of pyrimidine biosynthesis

46
Q

CTP is created in what pathway

A

pyrimindine pathways

47
Q

ATP is created in what pathway

A

purine pathway

48
Q

why does CTP do what it does

A

it acts as a feedback inhibitor on ATCase to allow the purine pathway to catch up on the pyrimidine pathway

49
Q

why does ATP do what it does

A

it acts as a feedback activator on ATCase to start the pyrimidine pathway.

50
Q

CTP and ATP is what kind of effector

A

CTP is a negative heterotropic effector and ATP is a positive heterotropic effector as they both compete for the allosteric site of the enzyme.

51
Q

what is important to note about CTP and ATP

A

CTP is made in the pyrimidine pathway while ATP is made in the purine pathway

52
Q

what is the concerted MWC model

A
  1. states that the allosteric enzyme can bind to the substrates (S) and sometimes to an activator (A) or an inhibitor (I).
  2. when anything binds to the enzyme, it causes changes that affect the equilibrium between the T and R forms.
    3.as the equilibrium shifts, all subunits change conformation simultaneously and adopt the same conformation ALL IN ONE STEP.
53
Q

what is t state

A

tense state of an enzyme that is inactive

54
Q

what is r state

A

relaxed state of an enzyme that is active to bind

55
Q

how does the T or R state occur.

A

The T state occurs when the inhibitor binds to the enzyme and the R state occurs when the activator binds to the enzyme.

56
Q

what is the substrate in terms of the concerted model and effector status

A

it is a positive HOMOtropic effector that binds only to the R state at the active site

57
Q

what is the activator in terms of the concerted model and effector status

A

it is a positive HETEROtropic effector that binds only to the R state at the allosteric site

58
Q

what is the inhibitor in terms of the concerted model and effector status

A

it is a negative HETEROtropic effector that binds only to the T state at the allosteric site.

59
Q

the activator stabilizes what form

A

the R form or the active form

60
Q

the substate stabilizes what form

A

the R form or the active form

61
Q

what is important to note about the allosteric regulation models

A

every time you bind anything to the enzyme (activator, inhibitor, or substrate), you create a different complex. so when you make a new complex, more of the regular enzyme (nothing bound)needs to be made to keep equilibrium.

62
Q

what is the effector that stabilizes T state of ATCase

A

CTP is the inhibitor therefore the negative heterotropic effector

63
Q

what is the effector that stabilizes R state of ATCase

A

ATPis the activator therefore the positive heterotropic effector

64
Q

what is the substrate in ATCase

A

aspartate is the positive HOMOtropic effector

65
Q

what is ATCase

A

an enzyme that moves a carbomyol group to asp.

66
Q

what are the similarities between the concerted and sequential models of allosteric regulation

A

1) both state that R+T states exist of the enzyme
2) R state binds to the substrate more readily

67
Q

what are the differences between the concerted and sequential models of allosteric regulation

A

Concerted model:
1) all subunits of enzyme change conformation simultaneously . you have all R or all T
Sequential model:
1) a change occurs in one subunit which triggers a change in the next subunit. you have some enzymes that are part R and part T.

68
Q

greater affinity for the substrate means

A

positive cooperativity

69
Q

lower affinity for the substrate means

A

negative cooperativity

70
Q

what are isozymes

A

isomers of an enzyme that catalyze the same reaction in different environements.

biochem (9 decks)

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