nucleic acids
dna nucleotide
1 phosphate group, 1 deoxyribose (pentose sugar), 1 nitrogenous base (A, T, C, G)
(pentose=5 carbons
hexose=6 carbons)
rna nucleotide
1 phosphate group, 1 ribose (pentose sugar), 1 nitrogenous base (A, T, C, G)
formation of nucleotides
join together via condensation reaction, releasing water. this forms phosphodiester bonds
(phosphodiester bond is formed by the condensation reaction between the phosophate of 1 nucleotide and fhen deoxyribose of another nucleotide) 5' to 3'
dna
adenine - thymine
cytosine - guanine
double helix
very long
located in nucleus
rna
adenine - uracil
cytosine - guanine
single helix
shorter
found in cytoplasm
pyrimidines
thymine, cytosine, uracil
single ring structure
purines
adenine, guanine
double ring structure
A2T
G3C
2 hydrogen bonds
3 hydrogen bonds
anti-parallel
2 DNA strands run in opposite directions
base pairs are
complimentary
liquid detergents
cause cell membrane to break down and dissolve lipids and proteins
salt solution
allows nucleic acids to precipitate (solid DNA)
protease enzyme
removes the histone proteins
reasons for dna replication
mitosis
meiosis
dna replication process
1. hydrogen bonds between bases are broken by helixase enzyme (unzips)
2. free 'activated' nucleotides, held by hydrogen bonds, line up with their complimentary bases on the dna strand
3. new strands link together and phosphodiester bonds form between nucleotides by DNA polymerase
4. 2 DNA molecules now recoil into double helix, 1 strand is the old dna and 1 strand is the new dna
the genetic code
the sequence of bases along its DNA
almost universal
universal
the same sequence of bases code for the same amino acids in all organisms
degenerate
each amino acid can be coded for by more than 1 triplet
non-overlapping
each base/triplet is only read once
transcription
dna is too large to leave the nucleus to bind to a ribosome so a copy of the gene is made in the form of mRNA
mRNA
single stranded
contains ribose
contains uracil
smaller than dna
single helix
DNA
double stranded
very large
double helix
tRNA
single stranded
smallest
clover leaf shaped
contains ribose
process of transcription
1. helicase unzips DNA (gene only)
2. template strand that is used
3. free activated RNA nucleotides complimentary base pair
4. RNA polymerase join adjacent nucleotides
5. forms mRNA
6. DNA molecule recoils
dna replication vs transcription
similarities:
both use helicase to unzip dna
both have complimentary base pairing
both use polymerase to join nucleotides together
template dna
differences:
replication: whole molecule unzips, dna polymerase, both strands are templates, dna nucleotides
transcription: just gene unzips. rna polymerase, 1 strand is a template, mrna nucleotides
translation
the formation of the polypeptide on the ribosome
anticodons
are complimentary to codons on the mRNA molecule
translation process
1. mRNA binds to a ribosome
2. tRNA brings the correct amino acid in the correct order to the mRNA
3. tRNA has an anticodon that is complimentary to the codon on mRNA
4. a peptide bond is formed between the 2 amino acids
structure of ATP
adenine (nitrogenous base), ribose (pentose sugar), 3 phosphate groups
ATP
adenosine triphosphate
how ATP releases energy
ATP -----hydrolysis----> ADP + Pi, releases energy
why is energy not stored as ATP
atp is relatively unstable, therefore cannot be stored easily
properties of ATP
small
water soluble
contains bond between phosphates with intermediate energy
releases energy in small quantities
easily regenerated