Triglycerides are glycerol joined to three fatty acids by condensation. Phospholipids are like neutral fats except one fatty acid is replaced by phosphate group or a group with both phosphate and nitrogen. Phospholipids arrange themselves in a double layer in water, so the polar heads face outward toward water molecules and nonpolar tails face toward each other away from water molecules. Cholesterol is a precursor of other steroids, including aldosterone and sex hormones. Testosterone is the male sex hormone.
Functions vary due primarily to different attached functional groups.
Amino acids are the monomers that condense to form proteins, which are very large molecules with structural and metabolic functions. Structural proteins include keratin, which makes up hair and nails, and collagen fibers, which support many organs. Myosin and actin proteins make up the bulk of muscle. Enzymes are proteins that act as organic catalysts to speed chemical reactions within cells. Insulin protein is a hormone that regulates glucose content of blood.