Question

question
is the following statement true? if not, explain why not:
since the secondary structure of a protein results from hydrogen bonding between components shared by all amino acids (a hydrogen on an amide n on one amino acid interacts with an oxygen on the carbonyl of another amino acid), the secondary structure does not depend on the specific amino acid groups (the r - groups) in the amino acid chain.
select the correct answer below:
the statement is true.
the statement is false, because the hydrogen bonds responsible for secondary structure are formed between components on the r - groups.
the statement is false because secondary structure is caused by the formation of peptide bonds between adjacent amino acids, not hydrogen bonding.
the statement is false because even though the r - groups are not responsible for the hydrogen bonding, they can still interact in ways that lead to a preferential secondary structure.

Explanation:

• Secondary structure of proteins (like alpha - helices and beta - sheets) is mainly due to hydrogen bonding between the backbone (amide N and carbonyl O) of amino acids, not the R - groups. So the first part of the original statement about hydrogen bonding between non - R - group components is correct.
• However, R - groups can influence the secondary structure. For example, large or bulky R - groups can sterically hinder the formation of certain secondary structures. Also, R - groups with specific chemical properties (e.g., charged R - groups) can interact with other R - groups in the protein chain. These interactions can either promote or prevent the formation of particular secondary structures. So the statement that secondary structure does not depend on R - groups at all is false.
• Option 2 is wrong because hydrogen bonds for secondary structure are not between R - group components. Option 3 is wrong because peptide bonds are for the primary structure (linking amino acids), and hydrogen bonding is for secondary structure.

Answer:

The statement is false because even though the R - groups are not responsible for the hydrogen bonding, they can still interact in ways that lead to a preferential secondary structure.