Proteins and Enzymes

ID #1024

Can you please further explain how secondary structure of Proteins really works? On the slides is says that the folding occurring in the second structure is independent of R groups...what does that mean? And finally could you please explain the main difference in the folding between the secondary and tertiary structure.

The secondary structures found in proteins are local regions of 3-dimensional shape caused by hydrogen bonding in the peptide linkages themselves. When certain amino acids find themselves next to each other, they fold and twist in certain ways, causing the whole protein to adopt a shape. This shape at the level of secondary structure is usually either helical or sheet-like, which we call either alpha helix or beta pleated sheets. We say that secondary structure is independent of R-groups (side chains) because the chemical groups that make up side chains do not directly participate in the hydrogen bonding at this level of organization. Now what separates secondary from tertiary structure is that tertiary structure involves chemical interactions of side chains either with other side chains or with the peptide backbone. Because there are a wide variety of side chains to choose from instead of the identical nature of every peptide bond, there are a virtually infinite number of 3-dimensional shapes possible for a protein at the level of tertiary structure.

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