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lipids

In Biochemistry

The building blocks of biochemistry: carbohydrates, lipids, nucleic acids, and proteins

Basic Biochemistry - Building Blocks of Biochemistry - Biomolecules

You may have already come across the terms carbohydrate, lipid, nucleic acid, and protein in your brief study of biochemistry. But perhaps you’re not quite sure what they are, or exactly why they’re important. This learning module provides a basic introduction to these four types of biomolecules.

Learning Goals

  • To provide a brief overview of and introduction to the four major classes of biomolecules (carbohydrates, lipids, nucleic acids, and proteins)

What is a biomolecule? What are they made of?

Biomolecule is short for biological molecule, and refers to any molecule that exists within a living organism.

As all life on earth is carbon-based, all biomolecules contain atoms of carbon covalently bonded to atoms of other elements.

While more than 25 elements can be found in biomolecules, six elements are the most common. These six elements are:

  • Carbon
  • Hydrogen
  • Nitrogen
  • Oxygen
  • Phosphorus
  • Sulphur

These elements are collectively often called the CHNOPS elements, as these letters stand for their chemical abbreviations.

Basic Biochemistry - CHNOPS Biomolecules


Why is carbon included in all biomolecules?

Carbon’s structure and properties provide it with the ability to support life. Its main advantages are:

  • Carbon has four valence electrons, and therefore needs four more electrons to complete its octet (also known as tetravalence). Its ability to form four covalent bonds is essential to the construction of large molecules.
  • Carbon-to-carbon bond strength is high, which means that carbon can be used as the backbone of large, stable molecules.
  • When carbon-carbon bonds are broken through combustion, they release a high amount of energy, making carbon-bonds an excellent source of fuel.

What are the four major classes of biomolecules?

While there are many individual types of biomolecules contained in living systems, there are four major classes of large biomolecules (also called macromolcules).

  • Carbohydrates
  • Lipids
  • Nucleic acids
  • Proteins
Biomolecule Class Made up of What does it do?
Carbohydrate Sugars -Provides a steady source of energy
Lipid Fatty acids -Provides a backup source of energy
-Serves as a cell divider/membrane
Nucleic Acid Nucleotides -Stores and transmits genetic material
Protein Amino acids -Allows for cell-cell communication
-Transports other molecules
-Speeds up reactions by acting as a catalyst

What is a carbohydrate?

Carbohydrates are likely the most familiar-sounding type of biomolecule. Carbohydrates are an important source of fuel for living creatures. The most common carbohydrate fuel is glucose, or simple sugar. Other types of carbohydrates include starches and cellulose. When carbohydrates are broken down, they provide energy to the cell.

Basic Biochemistry - Carbohydrates


What is a lipid?

Lipids are oily/greasy biochemical compounds that, like carbohydrates, serve as a storage form for fuel. They can also serve as a cellular barrier because of their dual chemical nature. Part of the lipid molecule is hydrophilic (can dissolve in water), while another part of hydrophobic (is not water soluble). This dual nature of lipids lets them form barriers in the form of cell membranes: in other words, lipids help distinguish “inside” versus “outside” at a biochemical level.

Basic Biochemistry - Lipids


What is a nucleic acid?

Made up of nucleotides, nucleic acids store and transmit information about the cell. They control all the functions and interactions of the cell.

There are two types of nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).

Basic Biochemistry - Nucleic Acids - DNA


What is a protein?

Proteins are perhaps the most versatile group of biomolecules. Proteins can act as catalysts in the form of enzymes; can store and transport other molecules (like oxygen in the bloodstream); generate movement; transmit nerve impulses; and control growth and cellular differentiation, to name but a few functions.

Despite their widely divergent range of functions, all proteins are constructed of the same, relatively small group of amino acids. By using various amounts of amino acids in different sequences, a huge variety of proteins can be generated and used for many different life-sustaining functions.

Basic Biochemistry - Protein


Key Takeaways

  • Biomolecules (molecules inside living creatures) are made of carbon covalently bonded to other elements (most commonly, hydrogen, nitrogen, oxygen, phosphorus, and sulfur).
  • All biomolecules contain carbon, since the properties of carbon allow it to bond covalently with many other elements, create strong, large structures, and give off considerable energy when its bonds are broken.
  • There are four major classes of biomolecules: carbohydrates, lipids, nucleic acids, and proteins.
  • Carbohydrates serve as a ready source of energy.
  • Lipids act as a backup energy source as well as a cell barrier.
  • Nucleic acids store and transmit information about the cell.
  • Proteins play a wide variety of roles, including transport of molecules and cell-to-cell communication.

Video Resources

Want more info on biomolecules? These two introductory videos from the Amoeba Sisters and Crash Course Biology can help you discover more.

Photo credits

Nut chocolate bar; Waffle with raspberries; Bottles of oil; DNA string; Eggs