Amino Acids (BC, OC)

Question 1

The alpha carbon IN EVERY amino acid is a chiral center EXCEPT

Answer 1

in glycine (it is achiral, since the R group is an H)

Question 2

EVERY AA has S configuration EXCEPT FOR

Answer 2

cysteine (R configuration)

Question 3

At low pH, amino acid =

Answer 3

Catonic = + charged

Question 4

At high pH, amino acid =

Answer 4

Anionic = - charge

Question 5

At pH = pI, amino acid =

Answer 5

zwitterionic (neutral)

Question 6

ACIDIC AA :

Answer 6

Aspartic Acid (Asp, D) ; Glutamic Acid (Glu, E)

Question 7

BASIC AA

Answer 7

Lysine (Lys, K) ; Arginine (Arg, K) ; Histidine (His, H)

Question 8

HYDROPHILIC AA if the R group is :

Answer 8

If the R group contains acids, bases, amines or alcohols. Examples: Arginine (Arg, R), Lysine (Lys, K), Aspartic Acid (Asp, D), Glutamic Acid (Glu, E), Glutamine (Gln, Q), Asparagine (Asn, N), Histidine (His, H), Serine (Ser, S), Threonine (Thr, T), Tyrosine (Tyr, Y), Cysteine (Cys, C), Tryptophan (Trp, W)

Question 9

HYDROPHOBIC AA if the R group is?

Answer 9

If the R group DOES NOT contain what is listed in Hydrophilic AA ^^

Alanine (Ala, A), Isoleucine (Ile, I), Leucine (Leu, L), Methionine (Met, M), Phenylalanine (Phe, F), Valine (Val, V), Proline (Pro, P), Glycine (Gly, G)

Question 10

Difference b/w Cysteine and Cystine?

Answer 10

Cysteine = amino acid with the thiol R group

Cystine = 2 cysteines that have formed a disulfide bond

Question 11

What kind of bonds link amino acid chains together

Answer 11

Peptide bonds link amino acid chains together

Question 12

Peptide bonds are formed by the reaction b/w what group of one AA and another group of an AA?

Answer 12

• nucleophilic addition-elimination which is a reaction between the carboxyl group of one amino acid and the amino group of another amino acid

Question 13

nucleophilic addition-elimination is what kind of rxn?& commonly seen in linking what?

Answer 13

condensation, dehydration rxn & peptide bonds

Question 14

In a Nucleophilic addition-elimnation rxn, the bond formed has what kind of characterisitics?

Answer 14

The nucleophilic amino group attacking an electrophilic carbonyl

The bond when formed has a lot of resonance delocalization (partial double bond character all over the place!)

Makes the bond very rigid/planar

However, this is still free rotation around the ALPHA CARBON

Question 15

How do you break a peptide bond? List the nonspecific and specific way this can be done :

Answer 15

via Hydrolysis

The process of breaking the peptide bond

Done by either acid/base hydrolysis (nonspecific) or with the help of proteolytic enzymes (specific)