The facts about cells Article.pdf - The facts about cells...

This article is available at 5 reading levels at .
The facts about cells
An illustration of cells. Photo from Pixabay.
Cells are the basic building blocks of life. Some life forms, or organisms, are made out of a single
cell, whereas others are made of millions.
Scientists estimate that our bodies contain anywhere from 75 to 100 trillion cells, which come in
hundreds of different types. Cells do everything from providing energy to allowing animals to
reproduce.
Below are 10 facts about cells, some of which are well-known while others may surprise you.
1. Cells are too small to be seen without magnification.
Cells come in a variety of sizes, ranging from 1 to 100 micrometers across. A micrometer is a
millionth of a meter, and there are more than 25,000 micrometers in a single inch.
The study of cells is called cell biology. Because cells are so small, it would have been impossible to
study them without the invention of the microscope. Thanks to this technology, cell biologists can
study detailed images of even the smallest of cells.
By ThoughtCo.com, adapted by Newsela staff on 10.18.17
Word Count 917
Level 930L

This article is available at 5 reading levels at .
2. There are two main types of cells.
Cells are divided into eukaryotic and prokaryotic
cells. Eukaryotic cells have nuclei that are surrounded
by membranes. A nucleus is a structure that stores
genetic information such as DNA. Animals, plants and
fungi are called eukaryotes because they are
organisms that are made of eukaryotic cells.
Prokaryotes are creatures that are made of a single
prokaryotic cell. Examples include bacteria and archaeans. Unlike a eukaryotic cell, the nucleus of
a prokaryotic cell is not surrounded by a membrane. This region in the cell is called nucleoid.
3. Prokaryotic single-celled organisms were the earliest and most basic forms of life on Earth.
Prokaryotes can live in environments that would be deadly to most other organisms. Some
archaeans are even able to live inside animal intestines. Others live in extreme environments such
as hot springs, swamps and wetlands.