Topic 2 Amino Acids

Draw general structure of amino acid, Describe 3 classes of amino acids, Recognize the structures of the 20 amino acids, Explain the concepts of pH, Ka, and pKa, Calc. pH and pKa using appropriate eq, Calc. the charge on amino acid groups given pH and pKa values, Calc. net charge on an amino acid given pH and pKa values

What does the protein sequence tell us about the amino acids?

→ Tells us how the a.a line up in the protein sequence

What does the arrangement of the protein sequence tell us about the protein?

The structure of the protein

What is a chiral alpha carbon?

A central carbon atom bonded to 4 unique substituents

Which is the only amino acid that does not have a alpha chiral carbon? Why?

Glycine

• because its R group is a H-atom which it already have one of

What isomer of amino acids are standard proteins in living organisms made from?

Only the L-isomers (not D) are in proteins

What rxn links amino acids together?

Condensation rxn

• removes a water molecule

What bond forms when a.a link via condensation rxn? What two molecules does it form on?

• Peptide bond (a strong covalent bond)

• Between the alpha-amino group of one a.a and the alpha-carboxyl group of another a.a

What do these peptide bonds form?

• a polypeptide

What is a “residue”

What an amino acid is called when it links with another amino acid

What is the N-terminus?

• the first residue which will always have an amino group attached

What is the C-terminus?

The last residue that will always have a carboxyl group attached to it

How many proteins do most amino acids contain?

20

What is the simplest and smallest amino acid

Glycine

• no L or D form of glycine

Which amino acid has its side chain covalently linked to its amino acid?

Proline (Pro, P)

Hydrophobic group

What happens when 2 cystines are close in space?

they form a disulfide bond

pH def

measures conc. of H+ in solution

Ka def

 acid dissociation constant (Ka) that is related to the affinity of the group for a proton

• larger Ka means the acid dissociates more easily, making it a stronger acid. 

pKa def

 number that tells you how easily a molecule gives up a proton (H+), serving as a standard measure of acid strength 

• a lower pKa means a stronger acid that gives up protons easily.