Question

Assume a spherical mammalian cell has a diameter of $27$ microns. If a polypeptide chain with alpha helical conformation has to stretch across the cell, how many amino acids should it be comprised of ?

• A. $18000$
• B. $1800$
• C. $27000$
• D. $12000$

Answer 1

The correct option is A $18000$

No. of amino acid in one term in $\alpha$-helix = 3.6

Pitch length for $\alpha$-helix = 5.4 Aº

The No. of Amino acid in polypeptide

= $27\times {10}^{-6}\times \frac{3.6}{5.4\times {10}^{-10}}$

=$1.8\times {10}^4$

Thus, the number of Amino acid = 18000