Back
Problem 77
Is the bond formed between each pair in Problem 18.76 covalent or noncovalent?
a. Cysteine and cysteine
b. Alanine and leucine
c. Aspartic acid and asparagine
d. Serine and lysine
Problem 84a
What is meant by the following terms as they apply to protein structure, and what bonds or molecular interactions stabilize that level of structure?
a. Primary structure
Problem 84b
What is meant by the following terms as they apply to protein structure, and what bonds or molecular interactions stabilize that level of structure?
b. Secondary structure
Problem 84d
What is meant by the following terms as they apply to protein structure, and what bonds or molecular interactions stabilize that level of structure?
d. Quaternary structure
Problem 85a
What level of protein structure is determined by the following:
a. Peptide bonds between amino acids?
Problem 85b
What level of protein structure is determined by the following:
b. Hydrogen bonds between backbone carbonyl oxygen atoms and hydrogen atoms attached to backbone nitrogen atoms?
Problem 86a
How do the following noncovalent interactions help to stabilize the tertiary and quaternary structure of a protein? Give an example of a pair of amino acids that could give rise to each interaction.
a. Hydrophobic interactions
Problem 87b
How do the following interactions help to stabilize the tertiary and quaternary structure of a protein? Give an example of a pair of amino acids that could give rise to each interaction.
b. Disulfide bonds
Problem 89
Give an example of a protein that has quaternary structure. How many polypeptide chains are present in this protein?
Problem 93a
Explain how a protein is denatured by the following:
a. Heat
Problem 93b
Explain how a protein is denatured by the following:
b. Strong acids
Problem 93c
Explain how a protein is denatured by the following:
c. Organic solvents
Problem 96
Fresh pineapple cannot be used in gelatin desserts because it contains an enzyme that hydrolyzes the proteins in gelatin, destroying the gelling action. Canned pineapple can be added to gelatin with no problem. Why?
Problem 97a
As a chef, you prepare a wide variety of foods daily. The following dishes all contain protein. What method (if any) has been used to denature the protein present in each food?
a. Charcoal-grilled steak
Problem 98a
For each amino acid listed, tell whether its influence on tertiary structure is largely through hydrophobic interactions, hydrogen bonding, formation of salt bridges, covalent bonding, or some combination of these effects.
a. Tyrosine
Problem 99
Oxytocin is a small peptide that is used to induce labor by causing contractions in uterine walls. It has the primary structure Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gln. This peptide is held in a cyclic configuration by a disulfide bridge. Draw a diagram of oxytocin, showing the disulfide bridge.
Problem 101
Four of the most abundant amino acids in proteins are leucine, alanine, glycine, and valine. What do these amino acids have in common? Would you expect these amino acids to be found on the interior or on the exterior of the protein?
Problem 102a
Globular proteins are water-soluble, whereas fibrous proteins are insoluble in water. Indicate whether you expect the following amino acids to be on the surface of a globular protein or on the surface of a fibrous protein.
a. Ala
Problem 105a
A family visits a pediatrician with their sick child. The four-month-old baby is pale, has obvious episodes of pain, and is not thriving. The doctor orders a series of blood tests, including a test for hemoglobin types. The results show that the infant is not only anemic but that the anemia is due to sickle-cell anemia. The family wants to know if their other two children have sickle-cell anemia, sickle-cell trait, or no sickle-cell gene at all.
a. What test will be used?
Problem 109
Which would you expect to be more soluble in water, a peptide containing mostly alanine and leucine or a peptide containing mostly lysine and aspartic acid? Explain. (Hint: Consider side-chain interactions with water.)
Problem 110a
Which of the following amino acids is most likely to be found on the outside of a soluble protein, and which of them is more likely to be found on the inside? Explain each answer. (Hint: Consider the effect of the amino acid side chain in each case and that the protein is folded up into its globular form.)
a. Valine
Problem 112
List the amino acids with side chains that are capable of hydrogen bonding. Draw an example of two of these amino acids hydrogen bonding to one another. For each one, draw a hydrogen bond to water in a separate sketch. Refer to Section 8.2 for help with drawing hydrogen bonds.