Cracking the AP Biology Exam

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Cells

LIVING THINGS

All living things—plants and animals—are composed of cells. According to the cell theory, the cell is life’s basic unit of structure and function. This simply means that the cell is the smallest unit of living material that can carry out all the activities necessary for life.

Cells are studied using different types of microscopes. Light microscopes, also known as compound microscopes, are used to study stained or living cells. They can magnify the size of an organism up to 1,000 times. Electron microscopes are used to study detailed structure of a cell and can magnify up to 50.1⁶ times but can only observe killed cells of specimens.