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nucleic acids (DNA + RNA) - Coggle Diagram
nucleic acids (DNA + RNA)
structure
pentose monosaccharide, phosphate group, nitrogenous base
phosphodiester bonds
covalent bond between phosphate group (at carbon 5) and hydroxyl group at carbon 3
sugar phosphate backbone
condensation reactions between two different monosaccharides
carbon, hydrogen, oxygen, nitrogen, phosphorus
pyrimidines: T/U + C (smaller + single ringed)
monomer: nucleotides
DNA
deoxyribose sugar (1 less sugar)
two antiparallel strands in a helix shape
hydrogen bonds between bases
large polymer: nucleic acid
purines: A + G (larger + double ringed)
RNA
binds to DNA to makes copies
small enough to enter and exit the nuclear pores + travel to ribosomes
ribose sugar
single stranded + smaller
A + T/U have 2 hydrogen bonds
G + C have 3 hydrogen bonds
DNA replication (semi-conservative)
occurs when cells divide so another copy of DNA needs to be made
double helix has to unwind (using DNA helicase) which breaks hydrogen bonds between bases
then free nucleotides find their complimentary base pairs and form hydrogen bonds
then DNA polymerase forms phosphodiester bonds between the free nucleotides on the new strand
so two new identical double helixes have formed with one new and one old strand each
transcription
sense strand: the strand that is needed to be replicated antisense strand: the strand that is used as a template
free nucleotides bind to complimentary base pairs on the antisense strand
DNA helicase unzips the double helix as far as a gene from the start codon, breaking the hydrogen bonds
phosphodiester bonds are formed between new nucleotides catalysed by RNA polymerase
the process of making mRNA so that a copy of the DNA strand can leave the nucleus to the ribosomes
thymine is replaced with uracil
mRNA detaches from the template and then leaves via the nuclear pore and the helix reforms
genetic code
the code is universal - all organisms use it
the code is degenerate - more than one codon can code for an amino acid
each gene is the amount of code needed for 1 protein
triplet code (codons) - each 3 bases code for an amino acid
there are 64 possible codons and 20 amino acids
DNAs code for a sequence of amino acids
there are three stop codons which signal the end of a sequence
translation
anticodons will bind to codons, tRNA carries a corresponding amino acid
a maximum of two tRNA can be bound at time
mRNA binds to a specific site on the small subunit of a ribosome
peptidyl transferase catalyses the formation of peptide bonds between the amino acids
mRNA is coded into a sequence of amino acids
protein may undergo further modifications at the Golgi apparatus
tRNA - a strand of RNA folded so that the anticodon (three bases) are at one end of the molecule