1.5 nucleic acid Flashcards
what does a nucleotide consist of
pentose sugar
phosphate
organic/nitrogenous base
what does ATP consist of
3 phosphate groups
pentose sugar
adenine
what are bonds between the phosphate group formed by
condensation reaction
what breaks the bond in ATP when it becomes ADP
ATPase hydrolyses the bond between the second and third phosphate
what type of reaction happens when ATP changes to ADP
exergonic reaction reaction.
how much energy is released when ATP goes to ADP
30.6 KJ is released
what is the addition of a phosphate to ADP called
phosphorylation
what is ATP called of the cell
universal energy currency
where is ATP used
in all organisms
all cells
used in all metabolic reactions
why is ATP efficient
-transfers energy from glucose to where it’s needed
- it releases energy in small amounts so there’s less waste
- only one enzyme is needed (ATPase) so less likely to go wrong
-ATP provides a common source of energy for many reactions increasing efficiency
why is DNA a nucleic acid
because it is more than 1 nucleotide joined together and it is made of pentose sugar, phosphate and an organic base
what is DNA
the genetic information coded in a sequence of bases
structure of DNA
is a double stranded polymer of nucleotides/polynucleotides
double helix held together by hydrogen bonds
what forms the backbone of the polynucleotide
alternating phosphate groups and pentose sugars
what is the pentose sugar in DNA
deoxyribose
4 bases?
adenine, thymine, guanine, cytosine
how do purines and pyrmidines bond
by hydrogen bonds
complementary base pairing
A-T
G-C
how do the two chains in DNA join together
the complementary base pairing link the two chains together
how many H bonds do the bases have
C-G have 3
A-T have 2
what are the polynucleotide chains
anti-parallel
what does the sequence of bases form
the genetic code
where is DNA found
in the nucleus of eukaryotic cells
function of DNA
replication and protein synthesis
DNA vs RNA
-double vs single polynucleotides
- DNA is larger
- T in DNA, U in RNA
- DNA is more stable than RNA (2 strands)
- DNA has deoxyribose, RNA has ribose
what pentose sugar does RNA contain
ribose
bases in RNA?
A,U,G,C
types of RNA
tRNA (transfer)
mRNA (messenger)
rRNA (ribosomal)
description/function of mRNA
synthesised in the nucleus and carries the genetic code from the DNA to the ribosomes
description/function of rRNA
found in the cytoplasm
translation happens here
description/function of tRNA
**small single stranded molecule with folds containing base sequences
the 3’ end has the sequence ACC
carries an anti-codon and transfers amino acids to the ribosomes
what does each strand of mRNA contain
the genetic code for one gene and each gene codes for a specific polypeptide
what are the two groups of bases
purines, pyrmidines
what are purines
larger (2 rings) Adenine, Guanine
what are pyrimidines
smaller (1) cytosine, thymine, Uracil
how many phosphates do DNA, RNA and ATP have
ATP- 3
DNA/RNA- depends on the length of the strand, alternating sugar phosphate
bonds in DNA
phosphodiester
three theories of DNA replication
semi-conservative
conservative
dispersive
what is the semi-conservative replication
1 new strand
1 original
conservative?
2 strands the same as original DNA
dispersive?
new and original strands mixed
which theory is accepted
semi-conservative
explain semi conservative replication
2 new molecules of DNA produced from one molecule
each new molecule consists of one old strand of DNA and one new strand
what is DNA helicase
unwinds and separates the two DNA strands (before replication can occur)
what is DNA polymerase
catalyses the formation of phosphodiester bonds between the free nucleotides and the template strand
explain the process of semi-conservative repliacation
DNA helicase is used to separate the DNA into 2 strands. these become the templates.
DNA polymerase helps the free nucleotides to join onto the strand in the correct place. there is then 2 DNA molecules
when is DNA transcribed to codons
when mRNA is made
what is a triplet code
3 bases that code for one amino acid
what is a codon
a triplet of bases in mRNA
what are the characteristics of the genetic code
unambiguous
degenerate
contain a stop codon
universal
code doesn’t overlap
what does unambiguous mean?
3 bases code for one amino acid
what does degenerate mean?
more than one triplet can code for an amino acids because there are 64 possible codes but only 20 amino acids
what do the stop codons do
acts as a full stop at the end of the sequence
what does universal mean
the code is the same in all organisms
what does it mean that the code doesn’t overlap
each base is only in one triplet
explain transcription
DNA helicase breaks the hydrogen bonds between the bases in the helix. DNA unwnds exposing the unpaired bases on the template strand. RNA polymerase links to the template strand of DNA insdrting mRNA nucleotides one a a time (complementary base pairing) and they form bonds with eachother. until a stop codon is reached, the RNA polymerase leaves DNA
whats cistron
the specific region that is copied
what’s an intron
non-coding nucleotide sequence in DNA
exon?
nucleotide sequence coding for amino acids
what is it called when RNA is made from DNA
it is a longer molecule called pre mRNA
what happens to the pre mRNA
it is modified to remove the introns before it leaves the nucleus (splicing)
what is mRNA leaving the nucleus made up of
exons only
what is the one gene-one polypeptide hypothesis
the theory that each gene is responsible for the synthesis of a single polypeptide
what is translation
process that converts the coded information of mRNA into the correct sequence of amino acids in a polypeptide
what are the 3 stages in translation
initiation
elongation
termination
what happens in stage 1 (initiation)
mRNA arrives at the ribosomes and they will attach to a start codon at one end of the mRNA. the tRNA will attach to the ribosome. it will have an anticodon complementary with the first codon on the mRNA
codon and anticodon will join with the hydrogen bonds. this will be repeated for a second tRNA anticodon
what happens in stage 2 (elongation)
the 2 amino acids form a peptide bond between them
then the first tRNA leaves the ribosome. return to the cytpolasm to bind to another copy of it’s specific amino acid
ribosomes move one codon along the mRNA strand
the next tRNA binds
what happens in stage 3
(termination)
repeats util a stop codon is reached
the ribosome mRNA separates
protein is ready to be transported where its needed
