Amino Acids, Peptides, and Proteins

Question 1

Parts of an Amino Acid

Answer 1

amino group, carboxylic acid, a hydrogen atom and an R group attached to a central alpha carbon

Question 2

Amino acids have what conformation? Exeptions?

Answer 2

Amino acids are chiral (L), except for Glycine

All have the (S) conformation, except for Cysteine

Question 3

Amino Acids with Nonpolar, Nonaromatic Side Chains

Answer 3

glycine, alanine, valine, leucine, isoleucine, methionine proline

Question 4

Amino Acids with Aromatic Side Chains

Answer 4

Tryptophan, Tyrosine, Phenylalanine

Question 5

Amino Acids with Acidic (-ve charge) Side Chains

Answer 5

aspartic acid (aspartate), Glutamic Acid (glutamate)

Question 6

Amino Acids with Basic (+ve charge) Side Chains

Answer 6

Arganine, lysine, histadine

Question 7

Amino Acids with Polar Side Chains

Answer 7

Serine, Threonine, asparagine, Glutamine

Question 8

Acid-Base Chemistry of Amino Acids

Answer 8

Acidic pH: fully protonated
Basic pH: fully deprotonated
Neutral pH: zwitteron

Question 9

Peptide Bond Formation

Answer 9

Condensation (dehydration) reaction with a nucleophilic amino group attacking an electrophilic carbonyl

Broken via hydrolysis

Question 10

Primary Protein Structure

Answer 10

linear sequence of amino acids

Question 11

Secondary Structure

Answer 11

local structure, stabilized by hydrogen bonding

alpha helices OR beta pleated sheets

Question 12

Tertiary Structure

Answer 12

three dimensional structure stabilized by hydrophobic interactions, acid-base interaction (salt-bridges), hydrogen bonding, and disulfide bonds

Question 13

Quaternary Structure

Answer 13

interactions between subunits

Question 14

pKa1 and pKa2 of the amino acid correspond to:

Answer 14

the carboxyl group and the amino group

can have a pKa3 if there is a charges side chain

Question 15

Isoelectric Point Definition

Answer 15

when the amino acid is neutral and it is very sensitive t pH changes

Question 16

Isoelectric Point Equations

Answer 16

pI= pKa1 + pKa2 / 2

if there is a charged side chain the value for the side chain and the value closest to it are used, the third farther away value is excluded from the equation

Question 17

Affect of Proline on Protein Structures

Answer 17

In alpha helices it creates a kink

In beta pleated sheets it is often found in the turns, but if located elsewhere it creates a kink

Question 18

Fibrous Proteins

Answer 18

sheets of long strands

Question 19

Globular Proteins

Answer 19

spherical

Question 20

Formation of Disulfide Bonds

Answer 20

formed when two cysteine molecules become oxidized to form cystine molecules, and it creates a loop in the protein chain