Chapter 3: Amino Acids

Which amino acid side chains are capable of ionization? Select all that apply. a) aspartate b) histidine c) serine d) alanine e) tyrosine

a) aspartate, b) histidine, e) tyrosine AAs Side Chains capable of Ionization: 1.tyrosine 2. cysteine 3.arginine 4. lysine 5. histidine 6. aspartic acids 7. glutamic acids

In which part of a globular protein are Trp and Phe located and why? a) exterior due to the hydrophilic effect b) interior due to the hydrophobic effect c) exterior forming polar H bonds with water d) interior forming ionic bonds with other amino acids e) exterior forming ionic polar bonds with water

b) interior due to the hydrophobic effect

What does NOT vary between amino acids? a) shape b) charge c) hydrophobicity d) L form in proteins e) hydrogen-bonding capacity

d) L form in proteins Varies between AAs: size, shape, charge, hydrogen-bonding capacity, hydrophobic character, and chemical reactivity

What would be the interactions between side chains of aspartate and arginine at a neutral pH? 1. hydrophobic 2. salt bridge 3. hydrogen bonding 4. steric 5. covalent

2. salt bridge (ionic)

Amino acids can contain all the following functional groups EXCEPT: 1. indole 2. thioester 3. phenyl 4. sulfhydryl 5. amine

2. thioester

What amino acid contains a thioether bond? 1. serine 2. threonine 3. cysteine 4. isoleucine 5. methionine

5. methionine

What is the driving force for formation of the unique spatial structure of water-soluble proteins? a) the tendency of hydrophilic groups to cluster together b) the tendency of hydrophobic groups to repel each other c) the tendency of polar groups to interact with water molecules d) the tendency of hydrophobic groups to cluster together e) the tendency of hydrophilic groups to repel each other

d) the tendency of hydrophobic groups to cluster together

What would be the overall charge of the peptide Asp-Gly-Arg-His at pH 1? a) -1 b) 0 c) 1 d) 2 e) 3

e) 3

In what pH range is alanine present predominantly in its zwitterionic form? a) 0-2 b) 9-14 c) 8-10 d) 2-4 e) 3-9

e) 3-9

Choose the essential amino acids. a) aspartate and lysine b) glycine and leucine c)proline and phenylalanine d) tryptophan and glutamate e)leucine and isoleucine

e) leucine and isoleucine. Essential AAs: valine, leucine, isoleucine, methionine, phenylalanine, tryptophan, threonine, lysine, and histidine.