OBJECTIVE LIFE SCIENCE
BIOCHEMISTRY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Amino acid side chains are located both above and below the sheet.
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They can exist in either parallel or antiparallel configurations.
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The sheets contain as few as two and as many as 22 polypeptide chains.
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Parallel
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Detailed explanation-1: -Beta sheets consist of beta strands (-strands) connected laterally by at least two or three backbone hydrogen bonds, forming a generally twisted, pleated sheet. A -strand is a stretch of polypeptide chain typically 3 to 10 amino acids long with backbone in an extended conformation.
Detailed explanation-2: -No preference for parallel or antiparallel beta-sheets is observed, but parallel sheets with less than four strands are rare, perhaps reflecting their lower stability. Sheets tend to be either all parallel or all antiparallel, but mixed sheets do occur. The Pauling-Corey model of the beta-sheet is planar.
Detailed explanation-3: -The antiparallel -sheet has a repeat unit comprising four peptide bond structures from two -sheet chains. Two of these four peptide bond structures are from the same -sheet chain and maintain the opposite directions to form a strong hydrogen bonding network with the other two peptide bond structures.
Detailed explanation-4: -The most common types of secondary structures are the helix and the pleated sheet. Both structures are held in shape by hydrogen bonds, which form between the carbonyl O of one amino acid and the amino H of another.