Amino acids Flashcards
What are the complex polymers that amino acids called?
Proteins
What are the 5 components of an amino acid?
Chiral carbon centre Hydrogen Carboxylic acid group Amino group Variable 'R' group
How many basic amino acids are there?
20
What causes the amino acids to be different?
Variable ‘R’ chain
What does chiral mean?
The central carbon has 4 different groups of atoms attached
Because amino acids are chiral, what does this mean they form?
Enantiomers
What are enantiomers?
Non-superimposable mirror images
What are the two names for the enantiomers?
L
D
What does D stand for?
Dextro
What does the D enantiomer do?
Rotate plane polarised light clockwise (+)
What does the L stand for?
Laevo
What does the L enantiomer do?
Rotate plane polarised light anticlockwise (-)
What type of enantiomer are proteins made from?
L enantiomers
What two labels can be used for the stereochemistry of amino acids?
R and S
How many amino acids have S stereochemistry?
18
What stereochemistry do natural protein forming amino acids have?
the same L-stereochemistry
What happens to the amino acids in a neutral pH solution?
They are ionised to a zwitterion
What is a zwitterion?
Dipolar molecule
What becomes charged in an amino acid in a zwitterion?
NH2 becomes NH3+
COOH becomes COO-
What is an acidic pKa?
2
What is an amides pKa?
9-10
When does NH3+ form? Why?
In pH = 1 (acidic)
Extra protons in acidic solution so protonates to compensate
When does COO- form? Why?
In pH = 11 (basic)
There arent many protons so it de-protonates to make up for it
What is the neutral point called?
Isoelectric point
What is an acid?
Proton donor
What is a base?
Proton acceptor
What is the equation for the equilibrium constant?
K = [H+][A-] / [HA]
What is the equation to work out pH?
pH = - log K = log 1/K
Which amino acids are natural amino acids? (5)
Glycine Alanine Valine Leucine Isoleucine
Gly?
Glycerine