CHAPTER 19 Problems

Learning Check

Solution

Nonpolar (NP)

Polar (P)

1) CH3 2) CH3

+ | |H3N—CH—COOH H2N—CH—COO–

Which structure represents: A. alanine at a pH above its pI?B. alanine at a pH below its pI?

Learning Check

1) CH3 2) CH3

+ | |H3N—CH—COOH H2N—CH—COO–

Which structure represents: A. alanine at a pH above its pI?B. alanine at a pH below its pI?

Solution

(2)(1)

Learning Check

Draw the condensed structural formula, and give the name and abbreviation for the dipeptide Ser-Thr.

OH CH3

| | CH2 O HCOH O + | ║ + | ║

H3N─CH─C─O– + H3N─CH─C─O– Ser Thr

Solution

OH CH3

| | CH2 O HCOH O + | ║ + | ║

H3N—CH—C—O– + H3N—CH—C─O– Ser peptide Thr

bond

OH CH3 | |

CH2 O H HCOH O + | ║ | | ║

NH3—CH—C─N—CH—C—O– + H2O

Seryl-Threonine (Ser-Thr)

Write the names and three-letter abbreviations of the tripeptides that could form from two glycines and one alanine.

Learning Check

Write the names and three-letter abbreviations of the tripeptides that could form from two glycines and one alanine.

Glycylglycylalanine Gly-Gly-Ala Glycylalanylglycine Gly-Ala-GlyAlanylglycylglycine Ala-Gly-Gly

Solution

Learning Check

What are the possible tripeptides formed from one each of leucine, glycine, and alanine?

Solution

What are the possible tripeptides formed from one each of leucine, glycine, and alanine?

Leu-Gly-AlaLeu-Ala-GlyAla-Leu-GlyAla-Gly-LeuGly-Ala-LeuGly-Leu-Ala

© 2013 Pearson Education, Inc. Chapter 19, Section 1 12

Learning Check

Write the name and three-letter abbreviation for thefollowing tetrapeptide.

H3N–CH– C–N–CH– C–N–CH–C–N–CH– CO–+

CH3 O H CH2 O H CH2 O H CH2 O

CH2CH–CH3

CH3

SH

S

CH3

© 2013 Pearson Education, Inc. Chapter 19, Section 1 13

Solution

Ala-Leu-Cys-MetAlanylleucylcysteylmethionine

Ala Leu Cys MetH3N–CH– C–N–CH– C–N–CH–C–N–CH– CO–+

CH3 O H CH2 O H CH2 O H CH2 O

CH2CH–CH3

CH3

SH

S

CH3

Indicate the type of protein structure as:1) primary 2) alpha helix3) beta-pleated sheet 4) triple helix

A. polypeptide chains held side by side by H bondsB. sequence of amino acids in a polypeptide chainC. corkscrew shape with H bonds between amino acidsD. three peptide chains woven like a rope

Learning Check

Indicate the type of protein structure as:1) primary 2) alpha helix3) beta-pleated sheet 4) triple helix

3 A. polypeptide chains held side by side by H bonds

1 B. sequence of amino acids in a polypeptide chain

2 C. corkscrew shape with H bonds between amino acids 4 D. three peptide chains woven like a rope

Solution

Select the type of tertiary interaction of the following. A. leucine and valineB. two cysteinesC. aspartic acid and lysineD. serine and threonine

1) disulfide 2) ionic3) H bonds 4) hydrophobic

Learning Check

Select the type of tertiary interaction of the following. 4 A. leucine and valine 1 B. two cysteines 2 C. aspartic acid and lysine 3 D. serine and threonine

1) disulfide 2) ionic3) H bonds 4) hydrophobic

Solution

Identify the level of protein structure of the following.A. beta-pleated sheetB. order of amino acids in a proteinC. a protein with two or more peptide chainsD. the shape of a globular proteinE. disulfide bonds between R groups

1) primary 2) secondary3) tertiary 4) quaternary

Learning Check

Identify the level of protein structure of the following. 2 A. beta-pleated sheet 1 B. order of amino acids in a protein 4 C. a protein with two or more peptide chains 3 D. the shape of a globular protein 3 E. disulfide bonds between R groups

1) primary 2) secondary3) tertiary 4) quaternary

Solution

What are the products of the complete hydrolysis of the tripeptide Ala-Ser-Val?

Learning Check

What are the products of the complete hydrolysis of the tripeptide Ala-Ser-Val?

The products are the three amino acids: alanine, serine, and valine.

Solution

Tannic acid is used to form a scab on a burn. An egg is hard-boiled by placing it in boiling water. What is similar about these two events?

Learning Check

Tannic acid is used to form a scab on a burn. An egg is hard-boiled by placing it in boiling water. What is similar about these two events?

Acid and heat cause the denaturation of protein. They both break bonds in the secondary and tertiary structures of proteins.

Solution