3.3.13 - Amino Acids, Proteins And DNA

Carbon attached to carboxylic acid, amino group Monomer which makes up protein (polypeptide)

they have acidic and basic properties

2 more amino acid linked in a chain by peptid bonds

Enzymes Hormones Antibodies etc

RCH(NH2)COOH Carbon w Amine carboxylic acid r and hydrogen attached R group is an alkyl chain that can also contain OH, SH, COOH, NH2

Bases and acids Contains carboxylic acid and amine functional groups

In acidic conditions the N in the amine group can accept a h+ ion Lone pair of e- on N forms dative covalent bond With h+ Gives N on amine to have positive charge Amine group has been protonated

Carbon must be bonded to n in amine and a c in carboxylic acid so may have to write something backwards

In alkaline cond Amino acid acts as a acid The COOH looses a h+ ion Oxygen Atom has now been left w a neg charge So carboxylic acid group has been deprotonated

Zwitterion

Proton is transferred from the carboxylic acid group to the amine group Creating both a pos and neg charge on diff parts on the mol Thus Zwitterion has no overall chargw bc pos and neg charges cancel out

Behave like ionic salts bc of their struc High mp and are soluble in water but not in non polar solvents At room temp most pure amino acids will be a white solid

Natural occurring alpha amino acid are optically active They all exist as the same enantiomer meaning they rotate plane polarised light anti clockwise

Glycine Bc the R group is just a H so carbon only bonded to 3 other groups

Peptides

Peptide link Water mol eliminated when peptide link is formed

Boiling water Acid Alkali Enzyme catalysing the reaction

Conc hcl