lecture 15 - regulation of metabolic pathways Flashcards

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1
Q

do chem rxns and pathways take place even if they delta G < 0

A

no

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2
Q

if reactions are thermodynamically favorable can they be wasteful to the cell or organism

A

yes

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3
Q

what are main pathways regulated by

A

feedback inhibition

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4
Q

feedback inhibition

A

inhibition of enzyme by a product of that reaction or metabolic pathway

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5
Q

when does feedback inhibition occur

A

when product is plentiful

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6
Q

what is feedback regulation a form of

A

negative feedback or refulation

-something is binding to enzyme and turning it off

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7
Q

what type of enzyme does feedbakc inhibition use

A

allosteric enzyme

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8
Q

how many binding sites does allosteric enzyme have

A

2 binding sites

-active site for sustrate
-allosteric site for end product (inhibitor)

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9
Q

what happens if too much inhibitor accumulates

A

pathway becomes blocked and nothing can bind to the allosteric enzyme

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10
Q

what happens if end product binds to allosteric site

A

substrate can’t bind at active ste

-active site shape is altered

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11
Q

what happens when product is plentiful

A

it inhibits the enzyme an thus metabolic pathway

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12
Q

example of feedback inhibition

A

isoleucine synthesis using threonine as first substrate of the pathway

-feedback inhibition of isoleucine synthesis by isoleucine

if there is plenty of isoleucine don’t make more

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13
Q

are all enzymes in a pathway allosteric

A

no, only slect ones

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14
Q

what type of forms can allosteric enzyme be

A

active and inactive

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15
Q

what are some allosteric enzymes regulated by

A

-allosteric inhibitor
-allosteric activators

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16
Q

where do allosteric activators and inhibitorsbind

A

at allosteric site of enzyme

17
Q

what can binding of an activatir stabilize

A

the active form of an enzyme

18
Q

what can binidng the inhibitor stabilize

A

the inactive form of enzyme

19
Q

what do most allosterically regulated enzymes consist of

A

multiple polypeptide subunits

20
Q

what does activator binding induce

A

active site to adopt the right shape to bind subtrate

21
Q

what happens to Km when activatir binds

A

Km is lower - higher affinity for substrate enzyme turned “on” or catalysts speed up

22
Q

what does inhibitor binding induce

A

induces active site to adopt the incorrect shape to bind substrate

23
Q

what happens to Km when inhibitor binds

A

Km is higher - lower affinity for substrate enzyme turned “off” or catalysis slows

24
Q

third step of glycolysis

A

-key regulatory step in cellular respiration

25
Q

main enzyme in third step of glycolysis and describe process of the step

A

enzyme = PFK

-Enzyme binds to F-G-D in active site and ATP moleq
-enzyme catalyzes phosphate from ATP to make F-I,6-P to make 2 phosphates
-PFK is under allosteric regulation by several molecules

26
Q

what does allosteric regualtion of PFK regaulte

A

the rate of glycolysis and thus the rest of cellular respiration too

27
Q

PFK is under allosteric regaultion by what

A

-allosteric inhibitors (citrate + ATP)
-allosteric activator (AMP)

28
Q

what nolecules is an indicator of low ATP levels when it is high

A

AMP

29
Q

need energy, so cells convert _____

A

ADP + ADP -> ATP + AMP

30
Q

in glycolysis in a resting muscle there is more ____ and less _______

A

ATP, pyruvate

31
Q

glycolysis in active muscle

A

less ATP and more AMP which binds to PFK, so ATP can’t bind to allosteric site and has to bind to active site and be used as a substrate

32
Q

check notes for fate of lactate generated by fermentation

A

ok

33
Q

gluconeogenesis

A

synthesis of glucose from small organic molecules

34
Q

in mammals where does gluconeogensis occur

A

mostly in the liver

35
Q

is gluconeogenesis glycolysis run in reverse

A

no!