Ch. 4

Question 1

What is the isoelectric point (pI)?

Answer 1

pH at which the amino acid has no net charge

Question 2

How does isoelectric focusing work?

Question 3

Primary structure

Answer 3

Amino acid sequence

Question 4

Secondary structure

Answer 4

H bonds among backbone atoms

Question 5

Tertiary structure

Answer 5

All 4 types of interactions between R groups

Question 6

Quaternary structure

Answer 6

All 4 types of interactions between R groups to join more than

Question 7

What do beta sheets look like?

Question 8

When are alpha helices favored?

Question 9

When are beta sheets favored?

Question 10

What is a zwitterion?

Answer 10

An electrically neutral but dipolar molecule that contains both positive and negative charges

Question 11

Practice question: Which type of structure can have all types of interactions and involves multiple polypeptides?

Answer 11

Quaternary

Question 12

Practice question: For a titration curve of histidine (pKa alpha amino is 9, pKa for alpha carboxyl is 2, and its R group is pKa 6), how many moles of OH would you need to fully deprotonate it?

Answer 12

3

Question 13

Practice question: Calculate the pI of histidine (pKa alpha amino is 9, pKa for alpha carboxyl is 2, and its R group is pKa 6).

Answer 13

7.5

Question 14

Practice question: For an amino acid with 2 titratable protons, how many moles of base do you need to obtain a zwitter ion?

Answer 14

1

Question 15

Practice question: Consider an alpha helix. Which amino acid pair cannot be within 3-4 amino acids of each other?

Answer 15

Asp and glue

Question 16

Practice question: Which amino acid makes disulfide bridges?

Answer 16

Cysteine

Question 17

Practice question: Secondary structure involves ___.

Answer 17

H bonds

Question 18

Practice question: Which amino acid is never found in alpha helices?

Answer 18

Pro

Question 19

Practice question: Which level of structure never has covalent bonds?

Answer 19

Secondary

Question 20

Practice question: Which level of structure involves multiple amino termini and carboxyl termini in R group-R group interactions?

Answer 20

Quaternary