Cambridge O Level Biology · Syllabus 5090 · Biological Molecules
Building Block
What is Building Block?
The small molecule from which a large biological molecule is assembled inside a cell. Glucose is the building block of starch, cellulose and glycogen; amino acids build proteins; fatty acids together with glycerol build lipids; nucleotides build DNA. A building block is a whole small molecule, not a chemical element.
This definition is part of the Biological Molecules chapter in Cambridge O Level Biology.
Building Block in context
Biological molecules are the large molecules that cells build from smaller units. Cambridge O Level Biology (5090) Chapter 4 asks three separate questions about each family. Which elements? Carbohydrates and lipids contain carbon, hydrogen and oxygen; proteins also contain nitrogen; DNA also contains nitrogen and phosphorus. Which building blocks? Glucose builds starch, cellulose and glycogen; amino acids build proteins; fatty acids and glycerol build lipids; nucleotides build DNA. Which role? Starch and glycogen store energy, cellulose forms plant cell walls, proteins work as enzymes and as structural material, lipids store energy, insulate and build membranes, and DNA carries genetic information.
Questions students ask about Building Block
What is the difference between an element and a building block?
Elements are the atoms a molecule contains; building blocks are the whole small molecules from which the large molecule is assembled. Glucose is the building block of starch, cellulose and glycogen; amino acids build proteins; fatty acids and glycerol build lipids; nucleotides build DNA. If a question asks for the smaller units, answering "carbon, hydrogen and oxygen" scores nothing, and answering "glucose" to a question about elements scores nothing either. Never swap the two answers.