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Chemistry LibreTexts

13.E: Amino Acids and Proteins (Exercises)

  • Page ID
    59422
  • These are homework exercises to accompany Chapter 13 of the University of Kentucky's LibreText for CHE 103 - Chemistry for Allied Health.

    Questions

    13.1: Amino Acids

    Q13.1.1

    Read the material at http://hyperphysics.phy-astr.gsu.edu/hbase/organic/essam.html and answer the following questions:

    a. What are essential amino acids?
    b. What are nonessential amino acids?
    c. What happens if you are deficient in an amino acid?

    Q13.1.2

    Draw the functional groups present in all amino acids.

    Q13.1.3

    Complete the following for threonine, lysine, and tyrosine.

    a. Draw the amino acid.
    b. Circle the side chain.
    c. Identify whether it is polar, nonpolar, acidic, or basic.
    d. At what pH will it exist as a zwitterion?
    e. What is the range of pH values when it will be positively charged?
    f. What is the range of pH values when it will be negatively charged?

    13.2: Peptides

    Q13.2.1

    Draw the two dipeptides formed from each pair of amino acids.

    a. tyrosine and lysine
    b. threonine and gluatmine
    c. alanine and histidine

    Q13.2.2

    Draw and give the full names of the amino acids in the following dipeptides.

    Q13.2.3

    List of all of the possible polypeptides that can be formed from threonine, alanine, and phenylalanine (use three character abbreviations for each amino acid).

    Q13.2.4

    Draw the following polypeptides.

    a. Ser-Tyr-Gln
    b. Lys-Met-Gly

    Q13.2.5

    Identify each of the amino acids in the polypeptide and then name it using the three character abbreviations.

    13.3: Protein Structure

    Q13.3.1

    Describe the four levels of protein structure.

    Q13.3.2

    What levels of structure involve hydrogen bonding?

    Q13.3.3

    What types of structure is the result of interactions between amino acids that are far apart in the primary structure?

    Q13.3.4

    What types of interactions hold the secondary structure together?

    Q13.3.5

    What types of interactions hold the tertiary structure together?

    Q13.3.6

    What levels of structure are affected by denaturation?

    Q13.3.7

    A protein has one subunit. Would it have a quaternary structure?

    Answers

    13.1: Amino Acids

    Q13.1.1

    a. Essential amino acids are those you get from your diet.
    b. Nonessential amino acids are produced in the body.
    c. Illness and/or degradation of body's proteins.

    Q13.1.2

    amino_acid_functional_groups.png

    amine and carboxylic acid

    Q13.1.3

    Complete the following for threonine, lysine, and tyrosine.

    threonine

    1. threonine.png
    2. polar
    3. 5.60
    4. < 5.60
    5. > 5.60

    lysine

    1. lysine.png
    2. basic
    3. 9.47
    4. < 9.47
    5. > 9.47

    tyrosine

    1. tyrosine.png
    2. polar
    3. 5.63
    4. < 5.63
    5. > 5.63

    13.2: Peptides

    Q13.2.1

    Draw the two dipeptides formed from each pair of amino acids.

    a. tyr_lys.png


    b. threonine_gluatmine.png


    c. alanine_histidine.png

    Q13.2.2

    a. alanine alanine.png glycine glycine.png
    b. proline proline.png phenylalanine phenylalanine.png
    c. tryptophan tryptophan.png lysine lysine1.png

    Q13.2.3

    Thr-Ala-Phe

    Thr-Phe-Ala

    Ala-Thr-Phe

    Ala-Phe-Thr

    Phe-Ala-Thr

    Phe-Thr-Ala

    Q13.2.4

    a. Ser-Tyr-Gln.png


    b. Lys-Met-Gly.png

    Q13.2.5

    13_2_5_b.png

    Arg-His-Thr-Glu-Ser

    13.3: Protein Structure

    Q13.3.1

    Primary - sequence of amino acids

    Secondary - alpha helix and Beta-pleated sheets held together by hydrogen bonds

    Tertiary - third level of structure of protein often forming globular or fibrous structure, held together by variety of attractive forces

    Quaternary - complex of multiple proteins held together to function as one, held together by variety of attractive forces (same as tertiary)

    Q13.3.2

    secondary, tertiary, and quaternary structures

    Q13.3.3

    tertiary structures

    Q13.3.4

    hydrogen bonds

    Q13.3.5

    London dispersion forces, hydrogen bonds, dipole-dipole forces, ion-dipole interactions, salt bridges, and disulfide bonds

    Q13.3.6

    secondary, tertiary, and quaternary

    Q13.3.7

    No, a quaternary structure must have multiple subunits.