Carbohydrates are composed of carbon, hydrogen, and oxygen. Carbohydrates include sugars, starches, cellulose, and chitin. Carbohydrates can be organized into four chemical groups including: monosaccharides, disaccharides, oligosaccharides, and polysaccharides. The small carbohydrates called monosaccharides and disaccharides are typically referred to as sugars. Carbohydrates perform many roles in living organisms most notably energy and structural components (e.g. cellulose and chitin).

Carbohydrates are known as sugars or saccharides. Virtually all carbohydrates end in the suffix "-ose," making them easy to identify. Ribose is a five-carbon sugar found in RNA. Some other common carbohydrates include deoxyribose, glucose, cellulose, and lactose. Sucrose is the technical name of table sugar, which is also a carbohydrate.

The other classes of molecules are fats, proteins, and nucleic acids. Fats, or lipids, can be further broken down into other categories, such as sterols and glycerolipids. Sterol lipids generally have the suffix "-ol" and include cholesterol and estradiol (estrogen). Glycerolipids include triglycerides. Proteins are formed from amino acids. Enzymes are a class of protein and generally have the suffix "-ase," such as helicase. Other proteins often have the suffix "-in" or "-en," such as insulin.

Polymers are molecules that are made of two or more repeating units of the same molecule or atom. For example, a polysaccharide is made of two or more monosaccharides bonded by dehydration synthesis. Lipids, on the other hand, are not. For example, triglycerides are composed of a glycerol molecule covalently bonded to three fatty acids via dehydration synthesis; however, fatty acids are elongated by the addition of methyl groups to the fatty acid chain.

Lipids are hydrophobic, which means that they are insoluble in water, a polar solvent. Lipids can store abundant energy. Lipids contain large nonpolar regions, which means that they are soluble in nonpolar solvents. Triglycerides are only one type of lipids. Other types include, but are not limited to: monoglycerides, diglycerides, phospholipids, and fatty acids.

Unlike carbohydrates and proteins, lipids are mainly nonpolar molecules. As a result, they are unable to be dissolved in aqueous solutions, such as blood. This makes them require a lipoprotein in order to be transported through the bloodstream. Without these proteins, lipids would be insoluble in the blood and cause clots.

Because lipids do not include true polymers, they are not big enough to be considered macromolecules. However, like fats, lipids are hydrophobic. Fats are considered macromolecules and are composed of glycerol and fatty acid molecules. The glycerol and fatty acid molecules are joined via an ester linkage, which is formed by a dehydration reaction.

Amphipathic molecules have both polar and nonpolar sections. For phospholipids, the phosphate region carries a negative charge, making it polar, while the lipid tail is a nonpolar hydrocarbon. Being amphipathic is a key characteristic that allows phospholipids to form the plasma membrane. The polar ends are able to face the aqueous environment while the nonpolar ends are faced towards each other. This creates an effective nonpolar barrier around the cell, while still remaining stable by having polar regions facing the aqueous environments.

Lipids are a diverse group of organic compounds containing 4-28 carbons. Lipids include fats, cholesterols, and vitamins. Lipids have a hydrophilic region with a polar carboxyl group and a hydrophobic region with a non-polar hydrocarbon chain. Lipids can be either saturated fatty acids (i.e. no double bonds) or unsaturated (i.e. one or more double bonds). The double bonds add a kink and reduce the melting point. Glycogen is a polysaccharide that is used for energy storage in animals.

Cholesterol is the precursor to all steroid hormones. Cholesterol is used as a structural component in cell membranes. It is also a precursor for many hormones—including testosterone and progesterone—and vitamins. Cholesterol is involved in cell communication including: intracellular transport, cell signaling, and nerve conduction. There are two primary types of cholesterol: LDL and HDL.

Maltose is a type of disaccharide that consists of two molecules of the monosaccharide glucose. Monosaccharides come together to produce a disaccharide and a molecule of water: condensation reaction. Polysaccharides include starch, glycogen, and cellulose. Starch is responsible for plant energy storage and includes amylose and amylopectin. Glycogen is used in animals for energy storage. Cellulose is a structural molecule utilized in plants.