3.3.13 - Amino Acids, Proteins and DNA Flashcards
Amino acid
A compound with an amine group and a carboxylic acid group within the molecule
Amino acids exist as…
Optical isomers
Single negative enantiomer
Nearly all amino acids exist as a single negative enantiomer so that they ‘fit’ into the correct cells within living organisms
Zwitterion
An ion with a positive and a negative charge
Amino acids can react as both…
Acids and bases depending on the conditions of the reaction due to the two functional groups within a single molecule
In acidic conditions (low pH)…
The lone electron pair is more likely to accept a hydrogen atom, producing a positive (acidic) end to the molecule
In basic conditions (high pH)…
The hydrogen atom on the -OH group is more likely to be lost, producing a negative (basic) end to the molecule
A zwitterion forms when…
The overall pH of the molecule is zero, known as the isoelectric point
Thin-layer chromatography
Can be used to identify unknown amino acids using UV light to view traces on the silica plate
Proteins
Sequences of amino acids joined together by peptide links
Reaction to reverse the formation of proteins
By boiling the protein in 6.0 mol dm-3 HCl for 24 hours in hydrolysis. This is carried out by enzymes so such harsh conditions are not required
Structure of proteins is held together by…
Hydrogen bonds, van der Waals forces and sulfur-sulfur bonds
Primary structure
A single polypeptide chain of amino acids
Secondary strucutre
An α helix or a β-pleated sheet held together with hydrogen bonds
Tertiary structure
Chains folded into a 3D coil with hydrogen and disulphide bonding
