L7 - nucleic acids Flashcards
what is nucleotide made up of?
phosphate + sugar + base
what is a nucleoside made of?
sugar + base
what anomer of DNA is deoxyribose?
beta anomer
purines
2 ring,
adenine and guanine
pyrimidines
1 ring,
cytosine and thymine
primary structure of DNA
sequence of bases held together by sugar phosphate backbone
base pairing (secondary structure of DNA)
2 H bonds between A and T.
3 H bonds between C and G.
secondary structure directionality
- anti parallel
- one strand goes in 5’ to 3’
- other 3’ to 5’
dimensions of secondary structure of DNA
- base pairs of 0.34 nm apart
- one helical turn 3.4nm
- so 10 bp per turn
- diameter of helix is 2nm
other info about secondary structure of DNA
- message code is comp
- right handed helix
- major groove and minor groove
tertiary structure of DNA
- chromosomal packing of DNA into chromatin
- chromatin compels of histone with DNA/ RNA
- form of solenoidal supercoiling
RNA primary structure
- comp code to DNA during transcription
- ribose sugar instead of deoxygenated
- uracil not thymine
secondary structure of RNA
- single stranded
- some regions of helix due to base pairing with same strand (tRNA)
- adenine pairs to uracil
tertiary structure of messenger RNA
relays code for protein from DNA to ribosome
tertiary structure of transfer RNA
comp triplet code of mRNA on the specific A.A
tertiary structure of ribosomal RNA
present in ribosome
central dogma
- primary sequence of DNA is ‘read’ to code for primary sequence of mRNA
- so RNA sequence is comp to DNA
what are the 2 biosynthetic pathways of nucleic acids?
- salvage
- de novo
describe de novo synthesis of purine nucleotides
- sugar phosphate is phosphorylated so purine Ring can be made on ribose ring
- this is then converted to 5-phosphoribosylamine
- first ring built of the ribose
- second ring built
- precursor ionise 5’ phosphate creates AMP and GMP
describe de novo synthesis of purines. stage 1: when sugar phosphate is phosphorylated
ribose-5-phosphate phosphorylated to form PRPP
describe de novo synthesis of purines. stage 2: PRPP to 5-phosphoribosylamine
PRPP to 5-phosphoribosylamine. occurs as glutamine turns to glutamate. enzyme: amidophoshoribosyl transferase
describe de novo synthesis of purines. stage 3: first ring built
5-phosphirbosyl-1-amine makes 5-aminoimadazole ribonucleotide
describe de novo synthesis of purines. stage 4: second ring built
5-aminoimadazole ribonucleotide makes ionsine 5 phosphate. CO2 and aspartate go in. ATP turned into ADP
describe de novo synthesis of purines. stage 4: precursor ionsine 5 phosphate makes AMP and GMP
very energy efficient
describe de novo synthesis of pyrimidine nucleotides
- nucleic acid ring assembled first then attached to ribose ring
- enzyme aspartate transcarbamylase acts when this occurs(allosteric)
- orotate and PRPP make uridylate
- conversion of nucleotide monophosphate to triphosphates
what is an allosteric enzyme
has more than one active site
describe de novo synthesis of pyrimidines stage 1: nucleic acid ring made and then attached to ribose ring
uses enzyme aspartate transcarbamylase.
carbonyl phosphate makes orotate
describe de novo synthesis. stage of pyrimidines. stage 2: conversion of monophosphate to triphosphates
- NMP + ATP makes NDP + ADP (monophosphate kinases - specific for each base but not sugar)
- NDP + ATP makes NTP + ADP (diphosphate kinase - non specific)
