Answer:
A hydrogen bond is a type of attractive (dipole-dipole) interaction between an electronegative atom and a hydrogen atom bonded to another electronegative atom. This bond always involves a hydrogen atom. Hydrogen bonds can occur between molecules or within parts of a single molecule.
The lactic acid that is building up in his muscles will eventually cause him to stop exercising. The burning sensation comes from the build up of that lactic acid in his muscles.
Phosphate groups are polar and allow the cell to exist in water.
