Many molecules are moved through the body by .

provide structure for plants.

determine what people look like.

Cells are surrounded and protected by
.

speed up chemical reactions in the body.

Hemoglobin, a protein, is built by
.

The human body is insulated by
.

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.