Chapter 3

What two functional groups are bound to the central carbon of every free amino acid monomer? a. an R-group and a hydroxyl group b. an N-H group and a carbonyl group c. an amino group and a hydroxyl group d. an amino group and a carboxyl group

What type of bond is directly involved in the formation of an \(\alpha\) -helix? a. peptide bonds between amino acid residues b. hydrogen bonds between amino acid residues c. van der Waals interactions between nonpolar residues d. disulfide bonds that form between cysteine residues

What type of information is used to direct different polypeptides to fold into different shapes?

What is an active site? a. the location in an enzyme where substrates bind and react b. the place where a molecule or ion binds to an inactive protein to induce a shape change c. the portion of a motor protein involved in moving cargo in a cell d. the site on an antibody where it binds to bacterial cells or viruses

Explain how molecular chaperones facilitate protein folding in many different polypeptides, each with their own specific shape.

Why are proteins not considered to be a good candidate for the first living molecule? a. Their catalytic capability is not sufficient for most biological reactions. b. Their amino acid monomers were not likely present in the prebiotic soup. c. They cannot serve as a template for replication. d. They could not have polymerized from amino acid monomers under early Earth conditions.

If proteins could fold only into rigid, inflexible structures, how might this affect the cell's ability to regulate their function?

Based on what you know of the peptide bonds that link together amino acid residues, why would proline's side chain reduce the flexibility of the backbone?

Make a concept map (see BioSkills 12 ) that relates the four levels of protein structure and shows how they can contribute to the formation of hemoglobin. Your map should include the following boxed terms: Primary structure, Secondary structure, Tertiary structure, Quaternary structure, Active site, Amino acid sequence, R-groups, \(\alpha\) -Helices.

Gluten is a mixture of proteins abundant in wheat, barley, and rye. Although these grains are staples in the Western diet, almost 1 percent of Americans have celiac disease- a disorder of the intestines caused by an abnormal immune response after eating gluten. This immune response damages the fingerlike villi of the small intestine, which can lead to intestinal upset and malnourishment. Currently, the only treatment is to maintain a strict gluten- free diet. The typical college student diet is rich in gluten-containing foods. Make a list of six items that you would not be able to eat if you were diagnosed with celiac disease.

Gluten is a mixture of proteins abundant in wheat, barley, and rye. Although these grains are staples in the Western diet, almost 1 percent of Americans have celiac disease- a disorder of the intestines caused by an abnormal immune response after eating gluten. This immune response damages the fingerlike villi of the small intestine, which can lead to intestinal upset and malnourishment. Currently, the only treatment is to maintain a strict gluten- free diet. When you eat gluten, enzymes present in your stomach and intestines digest all but a few short peptides. How do enzymes accomplish this activity? a. The active site of an enzyme binds to a gluten protein and facilitates the hydrolysis reaction that breaks apart peptide bonds. b. An enzyme binds to the active site of a gluten protein and speeds up the condensation reaction that breaks apart peptide bonds. c. The active site of an enzyme binds to a gluten protein and reacts with it to break apart hydrogen bonds. d. An enzyme binds to the active site of a gluten protein and catalyzes the reactions that break apart hydrogen bonds.

Gluten is a mixture of proteins abundant in wheat, barley, and rye. Although these grains are staples in the Western diet, almost 1 percent of Americans have celiac disease- a disorder of the intestines caused by an abnormal immune response after eating gluten. This immune response damages the fingerlike villi of the small intestine, which can lead to intestinal upset and malnourishment. Currently, the only treatment is to maintain a strict gluten- free diet. One of the peptides that can be recovered after gluten digestion is 33 residues long; 13 of the 33 residues are proline. How many times would you expect proline to appear in this peptide if it were made up of a completely random assortment of the 20 most common amino acids?