Final: nucleotide metabolism

Question 1

purines: where do carbons come from?

Answer 1

9 carbons from amino acids, 1 from CO2

Question 2

purine synthesis overview

Answer 2

IMP is made then converted to purines

Question 3

NADH from GMP synthesis

Answer 3

NADH is acquired energy → can contribute to ATP production in ETC

Question 4

glutamine is a great…

Answer 4

amino donor

Question 5

high ADP

Answer 5

low energy
cells won’t make new nucleotides
decrease ribose-5-phosphate pyrophosphokinase

Question 6

high adenine or guanine (purines)

Answer 6

decreases activity of Gln-PRPP aminotransferase

Question 7

high PRPP

Answer 7

activates Gln-PRPP aminotransferase

Question 8

control at branch point

Answer 8

determines whether we get ATP or GTP

important because we need right ratio of nucleotides to decrease mutations

Question 9

high AMP

Answer 9

blocks adenylosuccinate synthetase

Question 10

high GMP

Answer 10

blocks IMP dehydrogenase

Question 11

when is purine synthesis high?

Answer 11

when cells are about to divide

RBC don’t synthesize purines

Question 12

PRPP synthesis regulation

Answer 12

inhibited by ADP and GDP

Question 13

Gln-PRPP amidotransferase regulation

Answer 13

activated by PRPP

inhibited by AMP, ADP, and ATP at one regulatory site and GMP, GDP, and GTP at the other

Question 14

purine synthesis is balanced

Answer 14

1) GMP and AMP slow their own production

2) GTP and ATP facilitate the synthesis of the opposite purine

Question 15

purine synthesis step 2

Answer 15

PRPP to phosphoribosyl-beta-amine
Enzyme: Gln: PRPP amido-transferase
Glutamine + H2O to glutamate + PP
PP (pyrophosphate is released and immediately degraded)
Committed to purines!

Question 16

pyrimidine: where do carbons come from

Answer 16

4/6 carbons from aspartate

Question 17

which enzyme catalyzes committed step of pyrimidine synthesis?

Answer 17

CPS-II

Question 18

CPS-II control

Answer 18

UDP and UTP feedback inhibit

PRPP and ATP allosterically activate

Question 19

ribonucleotide reductase

Answer 19

deals with nucleotides

ultimate reducing power comes from NADPH

Question 20

nucleotide catabolism and salvage

Answer 20

salvage of bases allows reuse of bases

Question 21

when is ribonucleotide reductase turned on

Answer 21

high ATP

ATP binds to activity site to turn ON

Question 22

what happens when dATP concentration rises?

Answer 22

dATP displaces ATP at activity site and turns enzyme OFF

Question 23

regulation of dNTP synthesis occurs when

Answer 23

right before and during S phase of cell cycle

Question 24

regulation of dNTP synthesis

Answer 24

1) increases general purine and pyrimidine synthesis by increasing levels of synthetic enzymes
2) express ribonucleotide reductase
3) express thymidylate synthase
4) express TMP kinase

Question 25

what is leftover after nucleotides are deaminated?

Answer 25

ribose

Question 26

nucleotide salvage

Answer 26

we can add bases back to ribose

PRPP + hypoxanthine to IMP

Question 27

purine degradation

Answer 27

AMP or IMP to hypoxanthine

creates uric acid which must be excreted

Question 28

pyrimidine degradation

Answer 28

open rings

products are small molecules that are water soluble and can be degraded

Question 29

build up of dATP leads to

Answer 29

inability to make sufficient deoxyribonucleotides for DNA replication

Question 30

where is cholesterol stored in the liver?

Answer 30

lipid droplets

stored by ACAT

Question 31

well-fed state hormones

Answer 31

insulin: reports on blood glucose
leptin: senses stored energy as fat

Question 32

leptin

Answer 32

senses stored energy as fat in adipocytes

Question 33

if there isn’t enough energy around to make cholesterol,

Answer 33

AMPK phosphorylates HMG-CoA reductase to turn OFF the pathway

Question 34

AMPK functions

Answer 34

senses AMP and ATP binding
AMP activates AMPK
ATP inhibits AMPK