AP Biology: Elements of Life

In this AP Biology review, we will be going over learning objective 1.2.A, the elements of life.

Basic Chemistry

Matter is anything with mass and volume. All matter is built upon atoms, the smallest unit of matter. All atoms are built upon subatomic particles. These subatomic particles are protons, neutrons, and electrons. Here are some of the differences between the three particles:

Particle	Mass	Charge	Location
Proton	1 amu	positive	nucleus
Neutron	1 amu	neutral	nucleus
Electron	negligible	negative	Atomic orbit

How Elements of Life Build Macromolecules

Atoms make up elements, which are pure substances that can be broken down further. Some of the most important elements of life are carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur. Elements are used to build macromolecules: carbohydrates, lipids, proteins, and nucleic acids.

Carbohydrates

Carbohydrates are mainly composed of carbon, hydrogen, and oxygen. Carbohydrates are composed of carbon rings and the elements always present themselves in a 1:2:1 ratio of C:H:O. For example, in glucose there are 6 carbons, 12 hydrogens, and 6 oxygens.

Lipids

Lipids are composed of carbon, hydrogen, and oxygen. Sometimes, they will contain phosphorus. For example, phospholipids contain phosphorus. 

Proteins

Proteins are composed of carbon, hydrogen, oxygen, nitrogen, and sulfur. Additionally, they are composed of the following functional groups: amino group and carboxyl group. Functional groups will be discussed more in depth later.

Nucleic Acids

Nucleic Acids are made of carbon, hydrogen, oxygen, nitrogen, and phosphorus. Nucleic acids are made up of nucleotides. Nucleotides are composed of a 5-carbon sugar, a phosphate group, and a nitrogenous base.

Functional Groups

Functional groups are groups composed of specific atoms and arranged in a specific way. Functional groups can have a large influence on molecules’ properties. You do not need to know the specific properties of the functional groups, just how to identify them. There are a few you’ll need to know for the AP Biology exam.