Chapter 3

Question 1

structure of amino acid

Answer 1

central carbon atom, amino group, carboxylic acid, a hydrogen atom, and a side chain

Question 2

amino acids at pH 7

Answer 2

amino group is protonated (NH3+) and the carboxyl group is deprotonated (COO-)

Question 3

zwitterion

Answer 3

molecule containing both a positive and negative charge (net charge is 0)

Question 4

isoelectric point

Answer 4

pH at which the average charge on all molecules in solution is zero
pI = pka1 + pka2 / w

Question 5

ampholyte

Answer 5

molecule that contains groups with both acidic and basic pka values

Question 6

hydrophobic amino acids

Answer 6

nonpolar R groups

Question 7

polar hydrophilic amino acids

Answer 7

neutral R groups

Question 8

positively charged amino acids

Answer 8

R groups that have a positive charge at physiological pH

Question 9

negatively charged amino acids

Answer 9

R groups that have a negative charge at physiological pH

Question 10

primary protein structure

Answer 10

sequence of a chain of amino acids

Question 11

secondary protein structure

Answer 11

hydrogen bonding of the peptide backbone causes the amino acids to fold into a repeating pattern

Question 12

tertiary protein structure

Answer 12

three-dimension folding pattern of a protein due to side chain interactions

Question 13

quaternary protein structure

Answer 13

protein consisting of more than one amino acid chain

Question 14

shorter polypeptides

Answer 14

oligopeptides or peptides

Question 15

conjugated proteins

Answer 15

contain amino acids and at least one other prosthetic group