What is a cell?
All living things are made up of at least one cell. Of the millions of living organisms that inhabit Earth, all are made up of cells that are very similar in structure. On this page, you will learn more about cell types, cell structure, and how different species of organisms with seemingly identical cells can be so incredibly different! Lets begin by taking a closer look at the basic types of cells…
Put most simply, a cell is the basic unit of a cellular system, which is kind of backward, since its saying that a cell is part of something made out of cells! Another way of looking at it is as though a cell were a brick, and the body is an enormous wall or a house – made up of cells. Unfortunately this falls down again, because a brick is a relatively simple structure, whereas a cell can be very complicated! The image represents what could be described as a typical eukaryotic cell, containing the basic features of all cells. When it is made, every human cell contains its own living instructions, which it received from the cell that it came from – kind of like having a bit of your parents hanging about with you all the time, telling you what to do. This is in the form of DNA that can be found in the nucleus.
Cells are the structural and functional units of all living organisms. Some organisms, such as bacteria, are unicellular, consisting of a single cell. Other organisms, such as humans, are multicellular, or have many cells—an estimated 100,000,000,000,000 cells! Each cell is an amazing world unto itself: it can take in nutrients, convert these nutrients into energy, carry out specialized functions, and reproduce as necessary. Even more amazing is that each cell stores its own set of instructions for carrying out each of these activities.
Cells are the basic building blocks of all living things. The human body is composed of trillions of cells. They provide structure for the body, take in nutrients from food, convert those nutrients into energy, and carry out specialized functions. Cells also contain the body’s hereditary material and can make copies of themselves. Cells have many parts, each with a different function. Some of these parts, called organelles, are specialized structures that perform certain tasks within the cell.
