Microbiology Practice Exam 2026 - Free Microbiology Practice Questions and Study Guide

The basic unit of life is the cell. Cells are the fundamental building blocks of all living organisms, from the simplest bacteria to the complex multicellular organisms like plants and animals. They perform essential life functions, including metabolism, energy production, growth, and reproduction. Each cell is capable of carrying out these processes independently, which is a key characteristic of life.

Atoms are the smallest units of matter that retain the properties of an element, but they are not capable of exhibiting the characteristics associated with life on their own. Tissues, on the other hand, are groups of similar cells that work together to perform a specific function in a multicellular organism, but they are not the smallest unit of life. Similarly, organs are made up of multiple tissues that work together to perform complex functions, but they too are a higher level of organization beyond the cell. Thus, the cell is recognized as the most basic and essential unit of life.