3 biomolecules - nucleic acids and DNA

what are DNA and RNA

polymers made up of monomers called nucleosides

what do nucleosides contain

a sugar and a base

bases/nucleosides/amino acids structures

emailed megan

what are the two classes of nucleosides

purines and pyrimidines

which nucleosides are purines

adenosine (A) and guanosine (G)

which nucleosides are pyrimidines

cytidine (C), thymidine (T) and uridine (U)

how are nucleosides linked to one another

phosphate diesters between their 3’ and 5’ hydroxy groups

pKa of DNA and RNA

negatively charged, pKa = 1.3 (approx)

show H bonding pairs and how they form their H bonds

tip for drawing them?

helicity of DNA

right-hand

what does the right-hand helicity of DNA arise from

• the bases and ribose ring are at 90° to each other

• the geometry of the ribose ring gives DNA its helicity

• the DNA double helix has two different grooves of different sizes (major and minor) which correspond to the top and bottom faces of the DNA bases

what is the minor groove of DNA used for

common target for drugs and imaging molecules due to its distinctive shape

ΔS for DNA

when is it higher/lower?

hydrophobic?

entropy penalty for bringing two strands together

lower penalty for subsequent assembly

hydrophobic effect = release of bulk solvent → no loss of H bonds but the release of water causes more disorder

ΔH for DNA

many intermolecular interactions so enthalpically favoured

what are intermolecular interactions between the nucleic acid bases described as and what does this mean

cooperative

double helix assembly becomes easier as it progresses

why are the intermolecular interactions cooperative for DNA

the interactions between two bases pre-organises the next pair in the chains, making the next interaction more likely to occur

ΔG_binding for DNA? (7 components)

classify them into intermolecular interactions, hydrophobic effect and entropy penalties

find ΔG° for this sequence

biological role of DNA

stores genetic information and serves as a recipe book for protein synthesis

biological role of RNA

many functions, one of which is to convert the genetic code of DNA into proteins

stages of protein synthesis

all steps in protein synthesis

• mRNA makes a copy of the upper strand (5’ → 3’) using the lower strand (3’ → 5’) as a template

• anti-codons of tRNA which are attached to amino acids pair to the mRNA strand

• amino acids can join together

what is a gene

a sequences of bases in DNA that is transcribed to produce a functional molecule of RNA

what is a codon

a triplet of bases in mRNA that encodes for a specific amino acid

what is an anticodon

a triplet of bases in tRNA that corresponds to and recognises a codon

what is the amino acid corresponding to the start codon

methionine (Met)

what amino acid sequence would be constructed from this mRNA sequence

what DNA sequence could encode for the amino acid structure