Question

Explain why gelatin, which is mostly collagen, is nutritionally inferior to other types of proteins.

Globular proteins are typically constructed from several layers of secondary structure, with a hydrophobic core and a hydrophylic surface. Is this true for a fibrous protein such as B-keratin?

Briefly explain your answers for the following questions.

a) Is Trp or Gln more likely to be on a protein’s surface?

b) Is Ser or Val less likely to be in a protein’s interior?

c) Is Leu or Ile less likely to be found in a middle of an a-helix?

d) Is Cys or Ser more likely to be in a B-sheet?

You are performing site-directed mutagenesis to test predictions about which residues are essential for a protein’s function. Which of each pair of amino acid substitutions listed below would you expect to disrupt protein structure the most? Explain.

a) valine replaced by either alanine or phenylalanine

b) lysine replaced by either aspartate or arginine

c) glutamine replaced by either glutamate or asparagine

d) proline replaced by either histidine or glycine

Which of the polypeptide chains below is most likely to form an a-helix? Explain . Which polypeptide chain in would most likely to form a B-strand? Explain

a) CRAGNRKIVLETY

b) SEDNFGAPKSILW

c) QKASVEMAVRNSG

Calculate the p50 value for hemoglobin if YO2 = 0.82 when pO2 = 25 torr.

Explain why long-distance runners prefer to train at high altitude even when the race is to be held at sea level. Why must the runners spend more than a day or two at the higher altitude?

Is the p50 higher or lower than normal in

a) hemoglobin Yakima?

b) hemoglobin Kansas?

In hemoglobin Rainier, tyrosine 145 B is replaced by cysteine, which forms a disulfide bond with another cysteine residue in the same subunit. This prevents the formation of ion pairs that normally would stabilize the T state. How does hemoglobin Ranier differ from normal hemoglobin with respect to a) oxygen affinity, b) the Bohr effect and c) the Hill constant?

Answer 1

Gelatin is a protein and is formed from collagen, which is the primary protein in connective tissue. Its major sources are from ground bone and skin. It is soluble in hot water but forms a solid jelly when it cools. Gelatin has less nutritional value than many other protein sources because it is unusually high in the non-essential amino acids glycine and proline while lacking certain essential amino acids. It doesn't contain tryptophan and is deficient in isoleucine, threonine, and methionine.