1. The important properties of water depend on the molecule having a slightly positive charge on the side with the hydrogen atoms and a slightly negative charge on the side with the oxygen atom. This allows for a positive region of one water molecule to be attracted to the negative region of another, forming a hydrogen bond. These bonds are responsible for the cohesion and related properties of water. If the three atoms of water were in a straight line, its charges would be symmetrically distributed and the molecules would not be attracted to each other.

2. Carbon dioxide is found everywhere in the body, so it could not convey very specific messages. Since every cell in the body produces CO₂, a cell that detected CO₂ would have little way to tell where the message was coming from or what the message meant. (One exception is that there are some nerve cells that are specialized to respond to CO₂ concentration in the blood, but all the message means in this case is that the body is producing CO₂ either faster or slower than the respiratory system is getting rid of it.)

3. The only difference between cellulose and amylose is that the –CH₂OH group of each monosaccharide residue points the same way in amylose, while in cellulose they point in alternating directions. Amylase binds to the –CH₂OH groups and cannot digest cellulose because it cannot find two –CH₂OH groups close enough together.

4. Negative feedback is a mechanism for maintaining physiological stability. Allosteric inhibition exemplifies this by shutting down a pathway when there is enough of its end product, so the pathway does not run out of control and produce excessive amounts of it. It allows the pathway to "turn on" again when this end product becomes scarce. Negative feedback inhibition thus helps to maintain a stable concentration of the end product in a cell.

5. Both glycoproteins and proteoglycans are composed of protein and carbohydrate moieties. A glycoprotein is composed primarily of protein, while a proteoglycan is composed primarily of carbohydrate.

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