Use the following to answer the questions below:
In each of the following multiple-choice questions, characterize EACH of the three given statements as being TRUE or FALSE and then indicate the collective true-false status of the statements using the choices:
-Statements:
(1) For a tripeptide in which the three amino acids are different, six isomeric forms are possible.
(2) The "backbone" of a protein is an alternating sequence of C and N atoms.
(3) Both alpha-helix and beta-pleated sheet configurations can be present in the same protein.

Question

Use the following to answer the questions below:
In each of the following multiple-choice questions, characterize EACH of the three given statements as being TRUE or FALSE and then indicate the collective true-false status of the statements using the choices:
-Statements: 
(1) For a tripeptide in which the three amino acids are different, six isomeric forms are possible.
(2) The "backbone" of a protein is an alternating sequence of C and N atoms.
(3) Both alpha-helix and beta-pleated sheet configurations can be present in the same protein.

Quizplus · Accepted Answer

(1) False. There are actually 3! = 6 possible permutations of different amino acids in a tripeptide, but not all of them will result in unique isomeric forms because some permutations may result in peptides with identical structures.
(2) True. The backbone of a protein is formed by a repeating pattern of Cα-N-Cα-N.
(3) True. Proteins can have regions that adopt alpha-helix structures and other regions that adopt beta-pleated sheet structures, and these regions can be adjacent in the same protein.

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