Multiple Choice
How many amino acid residues are needed for the α-helix backbone to obtain exactly one full periodic repeat?
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4. Protein Structure
Alpha Helix Pitch and Rise
Multiple Choice
Hair is predominantly made of α-helix structures. Suppose hair grows at a rate of 20 cm/year. What is the rate at which amino acid residues are synthesized to account for the indicated growth of hair?
A
42 residues/sec
B
21 residues/sec
C
57 residues/sec
D
34 residues/sec
Verified step by step guidance1
Understand that hair is primarily composed of keratin, which is structured in α-helices. Each turn of an α-helix consists of approximately 3.6 amino acid residues and extends about 0.54 nm (nanometers) in length.
Convert the annual growth rate of hair from centimeters to nanometers. Since 1 cm equals 10^7 nm, a growth rate of 20 cm/year is equivalent to 2 x 10^8 nm/year.
Calculate the number of α-helix turns required for the annual growth by dividing the total growth in nanometers by the length of one α-helix turn (0.54 nm).
Determine the total number of amino acid residues synthesized per year by multiplying the number of α-helix turns by the number of residues per turn (3.6 residues/turn).
Convert the annual synthesis rate of amino acid residues to a per-second rate by dividing the total number of residues synthesized per year by the number of seconds in a year (31,536,000 seconds).
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