Question

Beta (β) sheets are a type of secondary structure in proteins. A segment of a single chain in an antiparallel sheet has a length of 305 Å. How many residues are in this segment?

a) Use the definition of Ångström
b) Apply the formula for the length of a protein segment
c) Consider the number of amino acid residues
d) Use the Pythagorean theorem

Answer 1

In an antiparallel β-sheet, each amino acid residue spans approximately 3.5 Å. To calculate the number of residues in a 305 Å long segment, we divide 305 Å by 3.5 Å, yielding around 87 amino acid residues.

Step-by-step explanation:

Calculating the Number of Amino Acid Residues in a Beta-Pleated Sheet Segment

The question pertains to the secondary structure of proteins, specifically the beta (β) sheet. This structure is formed by hydrogen bonding between atoms on the backbone of the polypeptide chain.

Each amino acid in an antiparallel β-sheet spans approximately 3.5 Å (angstroms). Given a chain length of 305 Å, we divide this length by 3.5 Å to find the number of residues:

Number of residues = Chain length / Length per residue = 305 Å / 3.5 Å

This calculation reveals that approximately 87 amino acid residues comprise the segment in this antiparallel β-sheet.

Notice that we did not use the Pythagorean theorem as it does not apply to this situation. Instead, we've used the formula predicated on the length of an amino acid in a β-sheet conformation.