BCHM 218 SOS Midterm Review Packet
Allingham:
Information Molecules: DNA, RNA and Protein
The Central Dogma:
 DNA –(transcription)-> RNA – (Translation)  Protein
 Exception: Viruses can do reverse transcription
 DNA is transcript for mRNA
 mRNA moves out of the nucleus and is translated with the help of tRNA and ribosomes
 The ribosome is made up of rRNA
o two subunits (small and large) assemble on the mRNA molecule to form a
complex
 Recursive system – all feeds back on itself (eg. proteins are required to make DNA)
 Abundance of other functional RNAs
Chemical Properties:
 Affinity determines specificity in molecular interactions
 Affinity is determined by weak molecular interactions
 Nucleic acids:
o Base : AGTC – DNA, AGCU – RNA
 hydrogen bonding
o Ribose (5 carbon) sugar
o Phosphate – bound to 5’ C of ribose
 Phosphodiester bond
 Bound to next nucleotide on 3’ sugar
 Don’t bother memorizing DNA modifications – very unlikely a question
will be asked on specifics
 Know that they can be modified and that these modifications
change the ability of proteins to bind DNA sequences
 Proteins:
o Amino acid
 contains an amine, a carboxylic acid, a methyl and an R group
o Amino acid residue
 the amino acid with an H2O molecule removed
o Peptide – a short chain of amino acid residues
o Oligopeptide – 2 to 20 amino acid residues
o Polypeptide – over 20 amino acid residues (i.e. a long chain)
o Always read N-terminal to C-terminal
o Know that amino acids can be modified – don’t need to memorize specific
modifications until learning about histones
Chemical Bonds
“Strong” Chemical Bonds:
 Covalent bond – electrons shared
o a single bond can rotate
o a double bond creates a planar shape
 groups are locked in place – can’t rotate
o Peptide bonds – have resonance – like a double bond
 therefore peptide bonds are planar and attached groups can’t rotate
 groups are located in the same plane
o Know polar vs non-polar covalent bonds
 Ionic bond – electrons transferred
o Positive charged aas – Lys, Arg, His (at pH’s below 6)
o Negative charged aas – Glu, Asp
o Can form ionic bonds with each other in the protein between oppositely charged
aas
o Ionic bonds can also be formed with cofactors like Mg