Multiple choice

Directions: Read the following information and answer the question given below: Proteins acquire specific and precise folds to perform a desired function. Therefore, the foldings of the proteins are highly essential and specific. Folds are further composed of two major 2o structures, i.e. alpha helices and beta sheets.

What is the helical rise (pitch) for a normal alpha-helix?

  1. 5.4 Ao

  2. 3.6 Ao

  3. 4.0 Ao

  4. 5.1 Ao
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A Correct answer
Explanation

The pitch of the alpha-helix is 5.4 Å or 0.54 nm, which is equal to 1.5 (translation height) * 3.6 (residues in one turn). Therefore, the length of 153 amino acid protein will be 153/.54 = 283 nm.

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