nucleic acids Flashcards
where are nucleic acids contains
in the nucleus of the cell
what are the two types of nucleic acid
DNA- deoxyribonucleic acid
and
RNA- ribonucleic acid
what do nucleic acids contain
Carbon
Hydrogen
Oxygen
Nitrogen
Phosphorus
what are nucleotides
nitrogen-containing organic substances forming the basis of nucleic acids
describe the structure of each nucleotide
a phosphate group is attached to either C5 or C3 by a covalent bond in a condensation reaction. a pentose sugar where a nitrogenous base is attached to C1.
functions of a nucleotide
form monomers of nucleic acids such as DNA and RNA. can regulated many metabolic pathways e.g. ADP, ATP, AMP
what does it mean if a nucleotide is phosphorylated
it contains more than one phosphate group e.g ATP, ADP
what is the covalent bond between phosphate group and sugar called in a nucleotide
phosphodiester bond
what is the covalent bond between nitrogenous base and sugar called in a nucleotide
glycosidic bond
what are the four possibilities of a nitrogenous base
Adenine, thymine, guanine and cytosine
what is a polynucleotide strand
a strand made up of many nucleotides
why is DNA an anti-parallel structure
its two polynucleotide strands run in opposite directions
what is the double helix
shape of DNA due to the coiling of the two sugar-phosphate backbone strands
what are the two examples of pyrimidine bases
thymine and cytosine (T&S)
what are the two examples of purine bases
adenine and guanine (A&G)
what is the difference between pyrimidine and purine bases
purine bases are 2 ring structures whereas pyrimidines are 1 ring structures
how many hydrogen bonds do adenine and thymine pair with
2
how many hydrogen bonds do cytosine and guanine pair with
3
the polynucleotide strand is held together by what bonds
phosphodiester bonds
the two polynucleotide strands are held together by what bonds
hydrogen bonds
what is the 3’ end vs 5’ end
3’ end is where the phosphate group is bonded to the carbon 3 of pentose sugar whereas 5’ end is where the phosphate group is bonded to carbon 5 of the pentose sugar
what is the difference in nitrogenous bases between DNA and RNA
DNA has thymine whereas RNA has uracil
what are the three main biological processes that require energy
-synthesis (energy is needed to create large molecules out of small molecules),
-transport (energy is needed to move substances via active transport),
-movement (muscle fibres require energy to contract)
what is the structure of ATP
adenine, ribose, three phosphate groups
why does DNA need to replicate
cell division- for growth and repair
reproduction- gametes require DNA to pass on genetic information
what is the process of semi-conservative replication
- DNA will unwind. The double helix will untwist a bit at a time. 2. The DNA will unzip. This means hydrogen bonds between nitrogenous groups are broken.
- free nucleotides in the nucleoplasm bond to the exposed single strands.
- once in place DNA polymerase joins the new nucleotides together by strong covalent bonds forming the sugar-phosphate backbone.
what enzyme catalyses the unwinding of DNA
gyrase
what enzyme catalyses the unzipping of DNA
helicase
what enzyme catalyses the joining of the new nucleotides
DNA polymerase
what direction does DNA polymerase join the new nucleotides to the free strands
5’ to 3’ direction
how is the lagging strand of DNA formed
dna polymerase fills in the complimentary base pairs in fragments called the okazaki fragments going in the 3’ to 5’ direction. each fragment is started off by a rna primer. once the dna strand is complete all primers are removed by the enzyme exonuclease. dna polymerase then fills in the gaps. once both strands are replicated dna lipase seals the fragments of DNA.
why does each gene need to be transcribed (copied)
as the instructions for each gene cant pass out of the nucleus
what is each gene copied into in order to pass out of the nucleus
mRNA
what is the sequence of base triplets called in the form of mRNA
codon
what are the steps of transcription
- DNA helix unwinds to expose the bases to act as a template. only one chain of the DNA acts as a template. like in dna replication the helix unwinds by the enzyme helicase and hydrogen bonds are broken between nitrogenous bases.
- free RNA nucleotides in the nucleoplasm align opposite their complimentary DNA base pairs. 3. RNA polymerase joins the RNA nucleotides by phosphodiester bonds to create a new RNA polymer chain
what are the steps of translation
- once the modified mRNA has left the nucleus it attaches to a ribosome in the cytoplasm.
- the ribosomes are attached to the start codon (the first three mRNA bases at the start of the sequence)
- the tRNA molecule, which has an amino acid attachment site determined by the complimentary anti-codon, aligns opposite the mRNA molecule and they are held in place by a ribosome.
- the ribosome will then move along the mRNA molecule to allow a different tRNA to attach to the complimentary mRNA codon.
- while the ribosome holds the mRNA and tRNA together the amino acids of the tRNA form peptide bonds with eachother.
- once the ribosome has moved along, the tRNA molecule of the previous codon detaches and is reused.
- this continues until ribosome reaches the stop codon and it does not code for an amino acid so translation ends.
- polypeptide chain is now created and enters golgi fpr packaging and modifying
what is the role of the ribosome in translation
holds the mRNA and tRNA in place
