lecture 15 - regulation of metabolic pathways

Question 1

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

Answer 1

no

Question 2

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

Answer 2

yes

Question 3

what are main pathways regulated by

Answer 3

feedback inhibition

Question 4

feedback inhibition

Answer 4

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

Question 5

when does feedback inhibition occur

Answer 5

when product is plentiful

Question 6

what is feedback regulation a form of

Answer 6

negative feedback or refulation

-something is binding to enzyme and turning it off

Question 7

what type of enzyme does feedbakc inhibition use

Answer 7

allosteric enzyme

Question 8

how many binding sites does allosteric enzyme have

Answer 8

2 binding sites

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

Question 9

what happens if too much inhibitor accumulates

Answer 9

pathway becomes blocked and nothing can bind to the allosteric enzyme

Question 10

what happens if end product binds to allosteric site

Answer 10

substrate can’t bind at active ste

-active site shape is altered

Question 11

what happens when product is plentiful

Answer 11

it inhibits the enzyme an thus metabolic pathway

Question 12

example of feedback inhibition

Answer 12

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

Question 13

are all enzymes in a pathway allosteric

Answer 13

no, only slect ones

Question 14

what type of forms can allosteric enzyme be

Answer 14

active and inactive

Question 15

what are some allosteric enzymes regulated by

Answer 15

-allosteric inhibitor
-allosteric activators

Question 16

where do allosteric activators and inhibitorsbind

Answer 16

at allosteric site of enzyme

Question 17

what can binding of an activatir stabilize

Answer 17

the active form of an enzyme

Question 18

what can binidng the inhibitor stabilize

Answer 18

the inactive form of enzyme

Question 19

what do most allosterically regulated enzymes consist of

Answer 19

multiple polypeptide subunits

Question 20

what does activator binding induce

Answer 20

active site to adopt the right shape to bind subtrate

Question 21

what happens to Km when activatir binds

Answer 21

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

Question 22

what does inhibitor binding induce

Answer 22

induces active site to adopt the incorrect shape to bind substrate

Question 23

what happens to Km when inhibitor binds

Answer 23

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

Question 24

third step of glycolysis

Answer 24

-key regulatory step in cellular respiration

Question 25

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

Answer 25

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

Question 26

what does allosteric regualtion of PFK regaulte

Answer 26

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

Question 27

PFK is under allosteric regaultion by what

Answer 27

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

Question 28

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

Answer 28

AMP

Question 29

need energy, so cells convert _____

Answer 29

ADP + ADP -> ATP + AMP

Question 30

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

Answer 30

ATP, pyruvate

Question 31

glycolysis in active muscle

Answer 31

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

Question 32

check notes for fate of lactate generated by fermentation

Answer 32

ok

Question 33

gluconeogenesis

Answer 33

synthesis of glucose from small organic molecules

Question 34

in mammals where does gluconeogensis occur

Answer 34

mostly in the liver

Question 35

is gluconeogenesis glycolysis run in reverse

Answer 35

no!