Comparing Biological Macromolecules

What you’ll learn to do: Discuss macromolecules and the differences between the four classes

As we’ve learned, there are four major classes of biological macromolecules:

  • Proteins (polymers of amino acids)
  • Carbohydrates (polymers of sugars)
  • Lipids (polymers of lipid monomers)
  • Nucleic acids (DNA and RNA; polymers of nucleotides)

Let’s take a closer look at the differences between the difference classes.

Learning Outcomes

Distinguish between the four classes of macromolecules

Carbohydrates are a group of macromolecules that are a vital energy source for the cell, provide structural support to many organisms, and can be found on the surface of the cell as receptors or for cell recognition. Carbohydrates are classified as monosaccharides, disaccharides, and polysaccharides, depending on the number of monomers in the molecule.

Lipids are a class of macromolecules that are nonpolar and hydrophobic in nature. Major types include fats and oils, waxes, phospholipids, and steroids. Fats and oils are a stored form of energy and can include triglycerides. Fats and oils are usually made up of fatty acids and glycerol.

Proteins are a class of macromolecules that can perform a diverse range of functions for the cell. They help in metabolism by providing structural support and by acting as enzymes, carriers or as hormones. The building blocks of proteins are amino acids. Proteins are organized at four levels: primary, secondary, tertiary, and quaternary. Protein shape and function are intricately linked; any change in shape caused by changes in temperature, pH, or chemical exposure may lead to protein denaturation and a loss of function.

Nucleic acids are molecules made up of repeating units of nucleotides that direct cellular activities such as cell division and protein synthesis. Each nucleotide is made up of a pentose sugar, a nitrogenous base, and a phosphate group. There are two types of nucleic acids: DNA and RNA.

Practice Questions

Explain at least three functions that lipids serve in plants and/or animals.

Explain what happens if even one amino acid is substituted for another in a polypeptide chain. Provide a specific example.

Check Your Understanding

Answer the question(s) below to see how well you understand the topics covered in the previous section. This short quiz does not count toward your grade in the class, and you can retake it an unlimited number of times.

Use this quiz to check your understanding and decide whether to (1) study the previous section further or (2) move on to the next section.