What is the smallest unit of life?
The cell is the smallest unit of life. It is the simplest structure that can carry out all the processes of life, such as growth, reproduction and using energy.
Some living things consist of just one cell, like bacteria, amoebas and yeast. Others, like plants and animals, are made of many cells working together. The smallest known free-living cells are tiny bacteria called mycoplasmas, about 0.2 to 0.3 micrometers wide, far too small to see without a powerful microscope.
Cells contain the parts needed to stay alive, including a membrane, genetic material and the machinery to make proteins and use energy. Smaller structures inside cells, such as DNA, proteins and organelles, are essential for life but cannot live on their own.
What about viruses?
Viruses are even smaller than cells, but most scientists do not consider them truly alive, because they cannot reproduce or use energy on their own. They must infect a living cell to make copies of themselves. This makes them a fascinating borderline case in biology.
Did You Know?
The human body contains roughly 30 trillion or more human cells, plus a similar number of bacterial cells.