All About Animal Cells

Did you know that your body is made of trillions of tiny, individual cells? Actually, scientists estimate that the number is around about 37.2 trillion cells in an adult human's body. Each cell has a unique job to do, and a unique destiny. Cells are in your blood, hair, muscles, toes, and eyes. Cells are also in tree bark, fish, monkeys, and rainforests. Cells exist in both plants and animals, but today, you'll learn about an ordinary animal cell.

What Is a Cell?

The cell is the basic unit of life. A cell's size and shape can vary. For instance, when you hold a chicken egg, you are actually holding one single cell. The largest animal cell by weight is the ostrich's egg, which can weigh over three pounds. Most cells, though, are very small, or microscopic. You might then ask, "What is life?" The answer is somewhat complicated. These are the basics of what makes life: it can grow, change, and reproduce. Cells are different from ordinary proteins, in that they can replicate themselves and evolve.

What Are the Main Parts of an Animal Cell?

The cell itself, while being so small, has a great deal going on inside of it. Similar to the way you have organs, the cell has what's referred to as organelles. The cell isn't just a plain sac of proteins, each set of proteins has an important function. These functions have been created over years and years of evolution. Here, you can find a list of the most important parts of the cell, their main function, and what they do for the overall cell:

Cell Membrane - The membrane of the cell forms an outer shell that protects it. It's function is to be semi-permeable, which means that it separates the cell from outside elements and only allows certain molecules in.

Centrosomes - Centrosomes organize microtubules, which are like hollow rods that give the cell its support and shape.

Centrioles - Centrioles are cylinders made of proteins that are found in a cell's centrosome.

Cytoplasm - This is the jelly-like substance that makes up the inside of the cell. It's not an organelle, but a material that can be found within the membrane.

Endoplasmic Reticulum - The endoplasmic reticulum, or ER for short, forms the transport system for the important proteins in the cell, like RNA. ER can be split into two groups: smooth ER and rough ER.

Golgi Complex - The Golgi complex, which is also known as the Golgi apparatus and named after the person who found it, is like the post office or packing center of the cell. It prepares proteins that need to be shipped off to specific destinations.

Lysosomes - Lysosomes are enzyme-filled sacs that digest nutrients and cell wastes.

Mitochondria - This organelle has an important job. It keeps the rest of the cell going by supplying energy in the form of adenosine triphosphate (or ATP).

Nucleus - The nucleus is a soft sac of the cell that has the responsibility of carrying its genetic code (also known as DNA).

Nucleolus - Within the nucleus is another nucleus, or nucleolus, where RNA is formed. RNA carries the messages or instructions that DNA provide.

Ribosomes - After RNA leaves the nucleolus and nucleus, it goes through the endoplasmic reticulum to the ribosomes, where protein synthesis takes place.

What's the Difference Between an Animal and Plant Cell?

A plant cell has other functions and organelles that the animal cell does not have. For instance, the plant cell has chloroplast and the cell wall. The chloroplast allows plants to produce energy from light with a process called photosynthesis. Plants derive their energies from the sun, whereas animals derive their energy by digesting other animals, plants, and fungi.

How Do Cells Reproduce?

Cells have many different functions and many different jobs to do. A nerve cell, for instance, has a very different job than a cell in your stomach lining. But most animal cells have one thing in common: they often reproduce. That process is called mitosis, which includes several phases and describes cell division. Learn more about how cells reproduce here: