The animal cell

All living beings are made up of cells. Plants, animals, and bacteria: we all consist of cells. Sometimes just one cell. Sometimes trillions of tiny cells co-operating to form an organism and to enable a body to function. For instance your body.

Here, in the brain, there are brain cells, that control the whole complex system that is you. They send signals via the nerve cells, that form an advanced network throughout the whole body. Some signals go to the heart. The heart is a muscle, so it has muscle cells, that respond to the signals coming from the brain. The heart pumps the blood around the body, and in the blood there are blood cells, transporting oxygen...

or fighting illnesses. -- And there you go. All the cells in your body are specialised, and have their unique function. But at the same time, there are properties that are the same for all animal cells - all cells in your body, in your friends' bodies, and in all living animals on earth. All animal cells have a nucleus. Here, in each nucleus, you'll find the "DNA".

The DNA carries the information that controls most of what happens in your body, from how your organs are structured and functioning, to the colour of your hair or your eyes. That information exists in each cell of your body. DNA is also known as genetic material, or "genes". You inherited it from your parents. They inherited it from their parents.

And so on. Most of what goes on in a cell is controlled from the cell nucleus. We could call the nucleus the administration of the cell. -- On the border of the cell, there is a flimsy layer called the cell membrane. The most important function of the cell membrane is protection. It regulates which substances are allowed to pass in and out of the cell .

Oxygen and carbon dioxide can pass relatively quickly and easily through the cell membrane. Larger molecules, like sugars, depend on certain checkpoints, transport proteins, to get in or out of the cell. -- Speaking about sugar. Sugar is rich in energy, and all cells require energy. Hence, they have their own small power plants ... ... that can use oxygen to develop energy which is stored in sugar.

These power plants are called mitochondria. In muscle - or brain cells there are lots of mitochondria, since they require lots of energy. -- All waste products have to leave the cell. Harmed cell parts, or waste need to be removed, and therefore there are certain cleaning patrols in the cell. They are called lysosomes. Their task is to break down the waste into smaller parts and transport it out of the cell. -- The cell nucleus, the mitochondrion and the lysosome are examples of the cell's organelles.

There are many more kinds of organelle in a cell. They all have their special appearances and functions. That's the way it is. The cell is so tiny, you need a microscope to see it, but within it there is intense activity around the clock. Everything happening inside the cell is controlled from the nucleus...

It has to safeguard its borders and prevent any harmful thing from entering the cell. That it does with the help of the cell membrane. The cell needs to be kept clean from waste and broken cell parts. In charge of this cleaning work, are lysosomes. A cell cannot work without energy.

Energy for the cell is generated by the mitochondria.