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
What side chain does Gly have?
H
Ala?
Alanine
What side chain does Ala have?
CH3
Val?
Valine
What side chain does Val have?
CH(CH3)2
Leu?
Leucine
What side chain does Leu have?
CH2-CH(CH3)2
Ile?
Isoleucine
What side chain does Ile have?
CH(CH3)CH2CH3
Which amino acids have aromatic side chains?
Phenylalanine
Tyrosine
Tryptophan
Phe?
Phenylalanine
What side chain does Phe have?
CH2-Benzene ring
Tyr?
Tyrosine
What side chain does Tyr have?
CH2-benzene-OH
Trp?
Tryptophan
What side chain does Trp have?
CH2-Pentagon with one NH substiuted-Benzene
Which amino acids contain sulfur atoms?
Cysteine
Methionine
Cys?
Cysteine
Met?
Methionine
What side chain does cysteine have?
CH2-SH
What side chain does methionine have?
CH2-CH-S-CH3
Which amino acids have basic side chains?
Lysine
Arginine
Histidine
Lys?
Lysine
Arg?
Arginine
His?
Histidine
What side chain does Lys have?
CH2-CH2-CH2-CH2-NH3+
What side chain does Arg have?
CH2-CH2-CH2-NH-C(=NH)- NH3+
What side chain does histidine have?
CH2-Pentagon with 2 substituted N atoms
Which amino acids have acid side chains?
Aspartate
Glutamate
Asparagine
Glutamine
Asp?
Aspartate
Glu?
Glutamate
Asn?
Asparagine
Gln?
Glutamine
What side chain does aspartate have?
CH2-COO-
What side chain does glutamate have?
CH2-CH2-COO-
What side chain does asparagine have?
CH2-CONH2
What side chain does glutamine have?
CH2-CH2-CONH2
Which amino acids have a hydroxyl side chain?
Serine
Threonine
Ser?
Serine
Thr?
Threonine
What side chain does Ser have?
CH2-OH
What side chain does Thr have?
CH(OH)-CH3
What type of amino acid is proline?
Imino acid
Which amino acids can be phosphorylated? Which part?
Ser
Thr
Lys
OH group
Which amino acid can be acetylated?
Lys
Which amino acid can be hydroxylated?
Proline
Ring of proline
How do amino acids form proteins?
Condensation reaction causes water to be lost and peptide bond to form
