L7 - nucleic acids

Question 1

what is nucleotide made up of?

Answer 1

phosphate + sugar + base

Question 2

what is a nucleoside made of?

Answer 2

sugar + base

Question 3

what anomer of DNA is deoxyribose?

Answer 3

beta anomer

Question 4

purines

Answer 4

2 ring,
adenine and guanine

Question 5

pyrimidines

Answer 5

1 ring,
cytosine and thymine

Question 6

primary structure of DNA

Answer 6

sequence of bases held together by sugar phosphate backbone

Question 7

base pairing (secondary structure of DNA)

Answer 7

2 H bonds between A and T.
3 H bonds between C and G.

Question 8

secondary structure directionality

Answer 8

• anti parallel
• one strand goes in 5’ to 3’
• other 3’ to 5’

Question 9

dimensions of secondary structure of DNA

Answer 9

• base pairs of 0.34 nm apart
• one helical turn 3.4nm
• so 10 bp per turn
• diameter of helix is 2nm

Question 10

other info about secondary structure of DNA

Answer 10

• message code is comp
• right handed helix
• major groove and minor groove

Question 11

tertiary structure of DNA

Answer 11

• chromosomal packing of DNA into chromatin
• chromatin compels of histone with DNA/ RNA
• form of solenoidal supercoiling

Question 12

RNA primary structure

Answer 12

• comp code to DNA during transcription
• ribose sugar instead of deoxygenated
• uracil not thymine

Question 13

secondary structure of RNA

Answer 13

• single stranded
• some regions of helix due to base pairing with same strand (tRNA)
• adenine pairs to uracil

Question 14

tertiary structure of messenger RNA

Answer 14

relays code for protein from DNA to ribosome

Question 15

tertiary structure of transfer RNA

Answer 15

comp triplet code of mRNA on the specific A.A

Question 16

tertiary structure of ribosomal RNA

Answer 16

present in ribosome

Question 17

central dogma

Answer 17

• primary sequence of DNA is ‘read’ to code for primary sequence of mRNA
• so RNA sequence is comp to DNA

Question 18

what are the 2 biosynthetic pathways of nucleic acids?

Answer 18

1. salvage
2. de novo

Question 19

describe de novo synthesis of purine nucleotides

Answer 19

1. sugar phosphate is phosphorylated so purine Ring can be made on ribose ring
2. this is then converted to 5-phosphoribosylamine
3. first ring built of the ribose
4. second ring built
5. precursor ionise 5’ phosphate creates AMP and GMP

Question 20

describe de novo synthesis of purines. stage 1: when sugar phosphate is phosphorylated

Answer 20

ribose-5-phosphate phosphorylated to form PRPP

Question 21

describe de novo synthesis of purines. stage 2: PRPP to 5-phosphoribosylamine

Answer 21

PRPP to 5-phosphoribosylamine. occurs as glutamine turns to glutamate. enzyme: amidophoshoribosyl transferase

Question 22

describe de novo synthesis of purines. stage 3: first ring built

Answer 22

5-phosphirbosyl-1-amine makes 5-aminoimadazole ribonucleotide

Question 23

describe de novo synthesis of purines. stage 4: second ring built

Answer 23

5-aminoimadazole ribonucleotide makes ionsine 5 phosphate

Question 24

describe de novo synthesis of purines. stage 4: precursor ionsine 5 phosphate makes AMP and GMP

Answer 24

very energy efficient

Question 25

describe de novo synthesis of pyrimidine nucleotides

Answer 25

1. nucleic acid ring assembled first then attached to ribose ring
2. enzyme aspartate transcarbamylase acts when this occurs(allosteric)
3. orotate and PRPP make uridylate
4. conversion of nucleotide monophosphate to triphosphates

Question 26

what is an allosteric enzyme

Answer 26

has more than one active site

Question 27

describe de novo synthesis of pyrimidines stage 1: nucleic acid ring made and then attached to ribose ring

Answer 27

uses enzyme aspartate transcarbamylase.
carbonyl phosphate makes orotate

Question 28

describe de novo synthesis. stage of pyrimidines. stage 2: conversion of monophosphate to triphosphates

Answer 28

1. NMP + ATP makes NDP + ADP (monophosphate kinases - specific for each base but not sugar)
2. NDP + ATP makes NTP + ADP (diphosphate kinase - non specific)