18. Amino Acids and Proteins

Both α-keratin and tropocollagen have helical secondary structure. How do these molecules differ in (a) amino acid composition and (b) three-dimensional structure?

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

Hemoglobin represents a commonly discussed tetramer that contains an even number of α and β subunits. Which of the following statements is true?

Which of the following could be classified as a prosthetic group?

Which of the following correctly orders the protein structural terms from lowest to highest complexity?

Examine the α-helix in Figure 18.1 and determine how many backbone C and N atoms are included in the loop between an amide hydrogen atom and the carbonyl oxygen to which it is hydrogen bonded.

Give an example of a protein that has quaternary structure. How many polypeptide chains are present in this protein?

What type of interaction would you expect between the R groups of the following amino acids in a quaternary structure?

a. phenylalanine and isoleucine

What type of interaction would you expect between the R groups of the following amino acids in a quaternary structure?

d. alanine and proline