nucleotide structure, function and metabolism

Question 1

define chromatin

Answer 1

protein + nuclear DNA

Question 2

what do nucleotides contain

Answer 2

base, sugar phosphate

Question 3

define nucleoside

Answer 3

when a base is attached to the sugar

Question 4

what are the purines

Answer 4

adenine and guanine

Question 5

what are the pyrimidines

Answer 5

cytosine, uracil, thymine

Question 6

what catalyzes the reaction of nucleotide phosphate to 2’-deoxynucleotide diphosphate

Answer 6

ribonucleotide reductase (ATP stimulates and dATP inhibits)

Question 7

what do ribonucleases do

Answer 7

covert RNA to short oligomers

Question 8

what do deoxyribonucleases do

Answer 8

convert DNA to short oligomers

Question 9

what do phosphodiesterases do

Answer 9

convert oligomers to nucleotide monophosphates or deoxynucleoside monophosphates

Question 10

what do nucleotidases do

Answer 10

convert the NMPs and dNMPs into nucleosides and deoxynucleosides

Question 11

what do nucleosidases do

Answer 11

remove ribose group and convert them into pyrimidines and purines

Question 12

what catalyzes the conversion of inosine to hypoxanthine

Answer 12

PNP

Question 13

what catalyzes the conversion of hypoxanthine to xanthine

Answer 13

xanthine oxidase

Question 14

what does adenosine deaminase (ADA) do

Answer 14

plays important role in adenosine homeostasis and modulates signaling by extracellular adenosine and so contributes indirectly to signaling

Question 15

what is the structure of xanthine

Answer 15

has 2 flavin adenine dinucleotides (FADs), 2 Mo atoms, and 8 Fe atoms per molecule of enzyme

Question 16

what is gout characterized by

Answer 16

intensely painful and inflamed joints and high levels of uric acid levels in blood

Question 17

what catalyzes the conversion of dTDP and dTTP to deoxythymidine

Answer 17

nucleotidase

Question 18

what catalyzes the conversion of deoxythymidine to thymine

Answer 18

uridine phosphorylase

Question 19

what is the source of ring atoms for purine bases

Answer 19

CO2, Gln, Gly, Asp, N10-formyl THF

Question 20

what is the source of ring atoms for pyrimidine bases

Answer 20

HCO3-, Gln, Asp, N5, N10-methylene THF

Question 21

what is the committed step in the purine synthesis

Answer 21

phosphoribosyl amine

Question 22

what molecule is formed from the committed step of the purine biosynthesis

Answer 22

hypoxanthine ribose phosphate/inosine monophosphate

Question 23

what are the 2 salvage enzymes in the purine biosynthesis

Answer 23

hypoxanthine guanine phosphoribosyl transferase

adenine phosphorirobosyl transferase

Question 24

what catalyzes the conversion of alpha-d-ribose-5-phosphate to PRPP

Answer 24

PRPP synthetase

Question 25

what is PRPP synthesized from

Answer 25

ribose phosphate and ATP

Question 26

what is the ribose for purines initially contributed by

Answer 26

phosphoribosylpyrophosphate

Question 27

where does methotrexate convert

Answer 27

in the liver

Question 28

what is methotrexate

Answer 28

inhibitor of DNA synthesis | binds dihydrofolate reductase 100 fold more tightly

Question 29

what is AMP synthesis stimulated by

Answer 29

GTP

Question 30

what is GMP synthesis stimulated by

Answer 30

ATP

Question 31

what is the pyrimidine ring synthesized from

Answer 31

carbamoyl phosphate and aspartate by aspartate-transcarbamoylase

Question 32

what is the committed step of the pyrimidine synthesis

Answer 32

formation of n-carbamoyl aspartate from aspartate and carbamoyl phosphate

Question 33

where is orotate synthesized

Answer 33

mitochondria

Question 34

what is the immediate hydrogen donor for the reduction of ribonucleoside diphosphate

Answer 34

reduced thioredoxin or glutaredoxin

Question 35

what is aspartate trascarbamoylase feedback inhibited by in the pyridine synthesis

Answer 35

CTP

Question 36

what is the limiting factor for DNA synthesis

Answer 36

dTTP