2.1.3 Nucleotides and Nucleic Acids Flashcards
components of nucleotides
phosphate
nitrogenous base
pentose base
nucleotides
carbon, hydrogen, oxygen, nitrogen, phosphorus
monomer of nucleic acids (DNA/RNA)
component of cofactors - coenzyme (NAD/FAD)
component of ATP, ADP, AMP
pyrimidines
cytosine, thymine, uracil
purines
adenine, guanine
reaction that occurs during formation of nucleotides
condensation reaction - removal of water
ADP and ATP
phosphorylated nucleotides
nucleotide (sugar, base, phosphate) with extra phosphate groups
properties of ATP
small, soluble in water - useful as energy-requiring processes occur in solution
relatively unstable ∴ cannot be stored easily
constantly being made/broken down
releases small quantities of energy
adenosine
adenine + ribose
adenosine monophosphate
adenine, ribose, 1 phosphate group
adenosine diphosphate
adenine, ribose, 2 phosphate groups
adenosine triphosphate
adenine, ribose, 3 phosphate groups
where is DNA found in eukaryotes
nucleus: chromosomes made up of DNA
mitochondria + chloroplasts
where is DNA found in prokaryotes
free in cytoplasm: circular chromosomes + plasma
found in some viruses
function of DNA
hereditary material of life
made of genes - code for protein
structure of DNA
double helix
anti-parallel strands
sugar phosphate backbone
rungs on ladder
complementary base pairs held by hydrogen bonds
how does the genetic code in genes code for proteins
3 bases code for 1 specific amino acid sequence of bases determine the sequence of amino acids
non-overlapping code
more than one codon codes for an amino acid
antiparallel
2 strands run in opposite directions
transcription
occurs in the nucleolus
DNA unzips exposing bases on the genes
H bonds are broken, revealing the template strand
free activated RNA nucleotides joined to the template strand by complementary base pairing
RNA polymerase moves from 5’ to 3’ direction
RNA nucleotides joined by RNA polymerase by phosphodiester bonds
enzyme reaches stop codons + detaches
two transcripts are modified before leaving nucleus via nuclear pore
DNA replication
occurs in the S phase of interphase - leads to creation of sister chromatids
materials required for DNA replication
enzymes - DNA helicase, DNA polymerase, DNA ligase
intact DNA - both strands act as templates
activated free nucleotides (phosphorylated)
energy source - ATP, unwinding DNA, activating nucleotides
semi conservative model of DNA replication
- DNA unwinds, unzips which breaks H bonds between complementary bases
- DNA bases on both template strands exposed
- in nucleus, 2 Pi are added to each free DNA nucelotide to activate them
- bases of activated nucleotides pair up with complementary bases on each of the old strands
- DNA polymerase catalyses formation of phosphodiester bonds joining new nucleotides in 5’ to 3’ directions. 2 extra Pi are broken off and released - hyrdolyses reaction as supplies energy to make bonds
- before adding next nucleotide, DNA polymerase proof reads previous pair + can correct/repair if needed
semi-conservative
in each new DNA molecule, 1 old strand is conserved and paired with 1 new strand
RNA structure
single-stranded
uracil instead of thymine
ribose sugar
function of RNA
involved in protein synthesis
messenger RNA - mRNA
long, single-stranded molecule
made in transcription
copy of coding/sense strand - U replaces T
passes out of nuclear pore into cytoplasm
transfer RNA - tRNA
small molecule
folds into clover leaf shape
ACC site can bind to an amino acid
anti-codon determines which amino acid binds, binds to codon on mRNA
