When atoms interact chemically to form molecules, they are held together by bonds . Acidic solutions are 6.9 and less, and alkaline are 7.1 and up. Buffers are substances that help to maintain neutrality, near where most animal cell activity takes place. Water is polar and has lots of hydrogen bonds. It is therefore a universal solvent and has a high boiling point, a high capacity to absorb heat, and lower density as a solid than as a liquid.
Water is a good evaporative coolant, and water also shows adhesion and cohesion.
Organic molecules contain the element carbon , inorganic molecules do not. Disaccharides and polysaccharides are made of linked simple sugars. Lipids are nonpolar, are made of carbon, hydrogen, and oxygen, but with much less oxygen. Fats contain a glycerol and fatty acids off of that. If they have all single bonds in the fatty acids, they are saturated .