Question

Describe hydrogen bonding in the α-helix of proteins and hydrogen bonding on the double helix of DNA, be sure to highlight the similarities and differences. Include in the answer the role of hydrogen bonding in these two structures.

Answer 1

Hydrogen bonding in DNA	Hydrogen bonding in alpha helix of proteins
The hydrogen bonding is between carbon and hydrogen between two nucleotides present on different strands.	Hydrogen bonding occurs between NH- and CO bonds on the protein backbone. The bonding in the same strand of polypeptide.
Adenine base pairs with thymine with two hydrogen bonds and Guanine form three hydrogen bonds with cytosine.	The C=O of one amino acid is bonded to the NH of fourth amino acid (alpha carbons) down the polypeptide chain.
Phosphate groups stick out of the helix. Sugar phosphate forms hydrogen bonding with water molecules	R groups are present sticking out of the helix
10 nucleotides are present per turn of the helix	3.5 amino acids are present per turn of the alpha helix. Bond angle of N-H-O is 2.8 Angstrom.
% methyl cytosine will break the bonding between guanine and cytosine	Proline will break the alpha helix
Hydrogen bonding is a part of primary structure of DNA.	Hydrogen bonding will lead to formation of secondary structure of protein
Hydrogen bonding will join the two strands of DNA. This is important for replication and transcription, where these bonds are broken. The hydrogen bonds increase stability of DNA.	Hydrogen bonding in alpha helix will join one amino acid in primary structure to fourth amino acid in the same structure, Thus, it will lead to folding of protein. They modify the enzymatic activity or proteins.

Both ds DNA helix and alpha helix is normally right handed. Both increase stability of DNA/protein.