BIO 305 Lecture 8

Amino Acids

Nonpolar amino acids at pH 7

Glycine, Alanine, Valine, Proline, Leucine, Isoleucine, Methionine, Phenylalanine, Tryptophan

Polar uncharged amino acids at pH 7

Serine, Threonine, Cysteine, Asparagine, Glutamine, Tyrosine

Polar positively charged amino acids at pH 7

Lysine, Arginine, and Histidine.

Polar negatively charged amino acids at pH 7

Aspartic acid and Glutamic acid

Hydroxyl group containing amino acids at pH 7

Serine, Threonine, and Tyrosine, which contain hydroxyl (-OH) groups that can participate in hydrogen bonding.

Amide group containing amino acids at pH 7

Asparagine and Glutamine, which contain amide (-CONH2) groups that can participate in hydrogen bonding.

Sulfur group containing amino acids at pH 7

Cysteine and Methionine, which contain sulfur atoms in their side chains that can form disulfide bonds.

Aromatic group containing amino acids at pH 7

Phenylalanine, Tryptophan, and Tyrosine which contain aromatic rings that can participate in stacking interactions and absorb UV light.

How are polypeptides formed?

Condensation reaction between amino acids, resulting in peptide bonds.

Biosynthesis starts at what end?

The amino (N) terminus, where the first amino acid is added.

How to determine the orientation of a peptide chain?

By identifying the N-terminus and C-terminus.

Amino acid derivatives

are modified forms of amino acids which are from Histidine (anti-allergic) and from Tyrosine (hormones).

At what codon does mRNA translate into protein?

The start codon, AUG, which codes for methionine.

Modification: Phosphorylation

Very ____

Makes AA __ and __

Most commonly on __ and __

Less commonly on __

Common, larger, polar, S, T, Y

Modification: Carboxylation

Less ____

Mainly in __ __ factors

Common, blood clotting

What does proline lack in? As a result what happens?

Amino group (NH) in its structure. Destabilizes the helix

What is the most flexible amino acid?

Glycine, due to its small size and lack of a bulky side chain.

What is the least flexible amino acid?

Proline, due to its rigid structure and cyclic side chain.

Which amino acid is very sensitive in pH changes?

Histidine, as its imidazole side chain can gain or lose a proton depending on the pH, impacting its charge and reactivity.

A condensation reaction is __ __ coming together to form __ __. It forms a __ bond

One molecule, two molecules, peptide

Protein production begain at what terminal

N

When two cystine containing amino acids come together, what bond do they form?

COVALENT disulfide bonds.

What structures of protein do disulfide bonds help stabalize?

Tertiary and quaternary structures.

Inter-chain and intra-chains make products with ___

Higher molecular weight

What type of chains do disulfide bridges have?

Inter-chain and intra-chain

Determining Hydropathy:

Octanol is a __ __ __. Thus __ __ __ __ are __ here

Water is a __ __. Thus __ __ __ are __ here

Non polar solvent, non polar amino acids, soluble, polar solvent, polar amino acids, soluble

What is the hydropathy of the amino acid if delta G is positive?

Hydrophobic

What is the hydropathy of the amino acid if delta G is negative?

Hydrophilic