Within all lifeforms on Earth, from the tiniest bacterium to the giant sperm whale, there are four major classes of organic macromolecules that are always found and are essential to life. These are the carbohydrates, lipids (or fats), proteins, and nucleic acids. All of the major macromolecule classes are similar, in that, they are large polymers that are assembled from small repeating monomer subunits. In Chapter 6, you were introduced to the polymers of life and their building block structures, as shown below in Figure 11.1. Recall that the monomer units for building the nucleic acids, DNA and RNA, are the nucleotide bases, whereas the monomers for proteins are amino acids, for carbohydrates are sugar residues, and for lipids are fatty acids or acetyl groups.
To reach and fertilize an egg, sperm must move — wriggling and swimming through a woman's cervix, uterus and fallopian tubes. This is known as motility. You're most likely to be fertile if at least 40% of your sperm are moving.
