18. Amino Acids and Proteins

Valine is an amino acid with a nonpolar side chain, and serine is an amino acid with a polar side chain. Draw the two dipeptides that can be formed by these two amino acids. Identify the peptide bond.

There are eight amino acids in vasopressin. How many peptide bonds are in this small protein?

What atoms are present in a planar unit in a protein chain?

How many amino acid units do these atoms come from? Why are these units planar?

Draw a tripeptide structure consisting of following amino acids in following order. Name tripeptide using 3 letter codes.

What are some differences between each of the following pairs? (16.1, 16.2, 16.3)

d. dipeptides and tripeptides

Draw the condensed structural formula for each of the following peptides, and give its three-letter and one-letter abbreviations:

a. alanylcysteine

Draw the condensed structural formula for each of the following peptides, and give its three-letter and one-letter abbreviations:

c. glycylalanylvaline

Draw the condensed structural formula for each of the following peptides, and give its three-letter and one-letter abbreviations:

b. threonylleucine

Peptides isolated from rapeseed that may lower blood pressure have the following sequence of amino acids. Draw the structure for each peptide and write the one-letter abbreviations.

a. Arg–Ile–Tyr

Peptides from sweet potato with antioxidant properties have the following sequence of amino acids. Draw the structure for each peptide and write the one-letter abbreviations.

b. Asn–Tyr–Asp–Glu–Tyr

Write the products for the following condensation or hydrolysis reactions:

a. <IMAGE>

Consider the following tripeptide:

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a. Circle the N-terminal amino acid, and give its name. Draw a square around the C-terminal amino acid, and give its name.

Consider the amino acids glycine, proline, and lysine.

b. Using three-letter abbreviations for the amino acids, give the sequence for each of the possible tripeptides.

Consider the following tripeptide:

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b. Give the one-letter and three-letter abbreviations of this tripeptide.

Draw the structural formula for each of the following peptides:

b. KCG

Draw the structural formula for each of the following peptides:

c. His—Met—Gln

Draw the structural formula for each of the following peptides:

c. Val—Arg

Draw the structural formula for each of the following peptides:

d. IYP

Identify the N-terminus and the C-terminus for each of the peptides in Problem 10.18.

a.

b.

Aspartame, which is commonly known as NutraSweet™, contains the following dipeptide:

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d. Draw the structure of the isomer of this dipeptide where the C-terminal and N-terminal amino acids are switched.

Draw the structure of the possible dipeptides formed from one alanine combining with one cysteine.

Identify the N-terminus and the C-terminus for each of the peptides in Problem 10.18.

c.

Identify the N-terminus and the C-terminus for each of the peptides in Problem 10.18.

d.