Nucleic Acids, ATP & Ions Flashcards
what is the role of DNA?
holds genetic information
what is the role of RNA?
transfers genetic information from DNA to the ribosomes where proteins are made
draw the structure of a nucleotide
DNA nucleotides contain: (3)
- a phosphate group
- 5 carbon sugar called deoxyribose
- contain one of four nitrogen containing bases:
adenine
cytosine
guanine
thymine
RNA nucleotides contain:
- a phosphate group
- 5 carbon sugar called ribose
- one of four nitrogen containing bases
adenine
cytosine
guanine
uracil
how is a dinucleotide formed? (3)
- via a condensation reaction between two nucleotides
- specifically between the phosphate group of one and the pentose sugar of the other
- forms a phosphodiester bond ; one molecule of water is produced
state the enzyme that catalyses a reaction involving DNA nucleotides
DNA polymerase
state the enzyme that catalyses a reaction involving RNA nucleotides
RNA polymerase
how is a polynucleotide formed? (3)
- via condensation reactions between many mononucleotides
- results in many phosphodiester bonds forming
- these help to form the sugar phosphate backbone of the nucleic acid
the DNA double helix (3)
- idea put forward by Watson & Crick in the 1950s
- two polynucleotide chains held together by hydrogen bonds between specific complementary base pairs
- the two strands of DNA run in opposite directions; they are anti-parallel
what are the complementary base pairs within DNA?
adenine + thymine
cytosine + guanine
how does the structure of DNA link to its function? (8)
sugar phosphate backbone + double helix structure = provides strength
longer molecule = stores a lot of information
helix structure = compact
base sequence = codes for amino acids ; therefore proteins
double stranded = allows semi-conservative replication ; each strand acts as a template
complementary base pairing = allows accurate replication
many weak hydrogen bonds between bases = easily broken ; separation of strands for semi-conservative replication
many hydrogen bonds in the whole molecule = strong and stable
ribonucleic acid (RNA) (3)
- a polymer made up of RNA nucleotides
- a single polynucleotide chain
- comparatively shorter than DNA
list the three types of RNA
- mRNA
- tRNA
- rRNA
mRNA (2)
“messenger RNA”
- a single stranded, linear polynucleotide that is a copy of a gene
- it takes information to a ribosome to make proteins
tRNA (2)
“transfer RNA”
- a single stranded polynucleotide folded into a cloverleaf shape
- brings amino acids to the ribosome during protein synthesis
rRNA
“ribosomal RNA”
- found in the ribosomes along with protein
describe the process of semi-conservative DNA replication (5)
- two strands of DNA separate because the weak hydrogen bonds between bases break
- this is helped on by the enzyme DNA helicase
- free nucleotides are attracted to their complementary bases
- the enzyme DNA polymerase joins the nucleotides with the bases once they’ve lined up
- all nucleotides are joined to form a complete polynucleotide chain ; two identical strands are formed of DNA
originally, how many hypotheses were there to DNA replication?
what were they referred to as?
3
conservative
dispersive
semi-conservative
what did the conservative hypothesis state?
the original parent strand remains intact, and a whole new DNA molecule is made
what did the dispersive hypothesis state?
each new DNA molecule contains fragments of both the parental double helix and newly synthesised DNA
what was the meselson stahl experiment based on? (3)
- all DNA bases contain nitrogen
- nitrogen has 2 isotopes: N14 and N15
- bacteria take up nitrogen from their environments to make all of their new DNA nucleotides during replication
what’s the difference between the N14 and N15 isotopes?
N14
has fewer neutrons
less dense
N15
1 more neutron
more dense
generation 0 of the meselson stahl experiment (3)
- grew bacteria in a medium containing only N15
- all bacteria had DNA that only contained N15
- this DNA formed 1 band that settled at the bottom of the tube (because it is “more dense”)
