Nucleic Acids (Lecture 29)

Question 1

what is a base?

Answer 1

aromatic ring that differs in the nucleic acid

Question 2

what is a nucleoside?

Answer 2

base + ribose

Question 3

what is a nucleotide?

Answer 3

base + ribose + phosphate group

Question 4

what does glutamine amide contribute to the purine structure?

Answer 4

N3 N9

Question 5

what does formate contribute to the purine structure?

Answer 5

C2 C8

Question 6

what does glycine contribute to the purine structure?

Answer 6

C4 C5 N7

Question 7

what does aspartate amine contribute to the purine structure?

Answer 7

N1

Question 8

what does HCO3- contribute to the purine structure?

Answer 8

C6

Question 9

what does aspartate contribute to the pyrimidine structure?

Answer 9

N1 C4 C5 C6

Question 10

what does glutamine amide contribute to the pyrimidine structure?

Answer 10

N3

Question 11

what does HCO3- contribute to the pyrimidine structure?

Answer 11

C2

Question 12

which molecule links to the ribose in a purine?

Answer 12

N9

Question 13

which molecule links to the ribose in a pyrimidine ?

Answer 13

N1

Question 14

which orientation is the base put onto the ribose?

Answer 14

beta glycosidic bond (base above)

Question 15

which stereo conformation re the sugars in nucleic acids

Answer 15

D sugars (furganose conformation)

Question 16

what it the nucleoside and nucleotide for adenine base?

Answer 16

nucleoside: adenosine
nucleotide: adenylate (AMP)

Question 17

what it the nucleoside and nucleotide for guanine base?

Answer 17

nucleoside: guanosine
nucleotide: guanylate (GMP)

Question 18

what it the nucleoside and nucleotide for cytosine base?

Answer 18

nucleoside: cytidine
nucleotide: cytidylate (CMP)

Question 19

what it the nucleoside and nucleotide for uracil base?

Answer 19

nucleoside: uridine
nucleotide: uridylate (UMP)

Question 20

what it the nucleoside and nucleotide for thymine base?

Answer 20

nucleoside: deoxythymidine
nucleotide: thymidylate deoxythymidylate (dTMP)

Question 21

what it the nucleoside and nucleotide for hypoxanthine base?

Answer 21

inosine

inosate (IMP)

Question 22

what it the nucleoside and nucleotide for xantoine base?

Answer 22

xanthosine

xanthylate (XMP)

Question 23

what it the nucleoside and nucleotide for orotate (orotic acid) base?

Answer 23

orotidine

orotidylate (OMP)

Question 24

what is the first step of de novo synthesis of purines?

Answer 24

synthesis of PRPP via alpha-d ribose-5-phosphate and ATP via ribose phosphate pyrophosphokinase (adds 2 phosphates)

Question 25

the de novo synthesis of purines is regulated at which steps?

Answer 25

synthesis of PRPP

synthesis of 5-phosphoribosylamine

when the cell needs more purines, the amount of PRPP will increase, thus increasing the amount of 5-phosphoribosylamine

Question 26

what is the committing step in purine de novo synthesis?

Answer 26

PRPP –> 5-phosphoribosylamine

Question 27

what is the second step of purine de novo synthesis?

Answer 27

PRPP with glutamine form glutamate and beta-5-phosphoribosylamine

pyrophosphate is release, which makes this reaction irreversible

this is done via amidophosphoribosyl transferase

Question 28

what is the N donor in the second step?

Answer 28

glutamine

Question 29

why does the release of PPi cause the second step of purine de novo synthesis to be irreversible?

Answer 29

low PPi concentration in the cytosol, because it is always converted into 2Pi, thus making the generation of PPi energetically favourable

Question 30

what is the usual pathway to donating an amine group?

Answer 30

addition of ATP to a carbonyl group to prime

addition of NH3 and release of Pi

Question 31

where is the N from glutamine derived from?

Answer 31

side chain

Question 32

where is the N from aspartic acid derived from?

Answer 32

back bone