Answer:
Interaction between hydrophobic (nonpolar) amino acid side chains is due to hydrophobic interactions.
Repulsion between negatively charged backbone of DNA double helix is due to electrostatic repulsion forces.
Interaction between water and carbonyl oxygen of guanine is due hydrogen bonding
Explanation:
The hydrophobic effect refers to the tendency of non-polar substances forms aggregates in an aqueous solutions in order to avoid interactions with water molecules. This results in a favorable entropy increase.
For non-polar amino acids, hydrophobic interactions are important in stabilizing their structure wherein they are densely packed within the core of a protein while those with with polar groups are found in the exterior.
The phosphate backbone of DNA is negatively charged. Since like charges repel, therefore, electrostatic repulsion forces of the ions are responsible the repulsion of the backbone DNA double helix.
Hydrogen bonds are formed between electronegative oxygen atoms and hydrogen atoms of neighboring molecules due to the partial negative and positive charges on each of the atoms.
This hydrogen bonding is responsible for the interaction between water and carbonyl oxygen of guanine as the hydrogen atoms of the water molecules are attracted to the oxygen atoms of the guanine molecules due to the partial charges on each of the atoms.
