Every living thing in the world is made up of cells. Cells are the building blocks of life.
There are two basic cell types: prokaryotic and eukaryotic.
When life first emerged on earth, it was made up of very simple organisms called prokaryotic cells. Though life evolved to be more complex, many organisms are still prokaryotic. For instance, there are trillions of bacteria that live in your small intestine that are still prokaryotic.
Complex organisms need their cells to do many things. Some of these things are only possible inside of organelles. Organelles are inside cells and are similar to organs in the bodies of animals. Each one has a specific function that helps the cell live. Cells with organelles are called eukaryotic cells.
Your body is made of eukaryotic cells. Eukaryotic cells are larger and more structured than prokaryotic cells. Plus, the many organelles in a eukaryotic cell can create more substances, digest food more efficiently, and even help these cells move around more quickly.
Here are a few of the organelles found in the cells of plants and animals:
Every cell in your body has one nucleus. The nucleus contains DNA. These molecules are like a recipe. They tell the cell how to function and make copies of itself.
Ribosomes create proteins based on the DNA code. Each ribosome “reads” the code, then produce proteins which carry out all of the functions in a cell.
Mitochondria use oxygen and sugar to create tiny molecules that are full of energy cells need..
Even a cell has to eat. Lysosomes are filled with acids and chemicals called enzymes that help break down food molecules from the bloodstream, into pieces that the cell can use.
Vacuoles are like tiny pockets that can hold water, waste, and dangerous substances that would otherwise hurt the cell.
Eukaryotic and prokaryotic cells reproduce in a similar way. First, they must copy their DNA. Then, they must divide in half. In eukaryotic cells, the process of reproducing cells is called mitosis.
In mitosis, a cell starts by making an exact copy of its DNA. Then, the cell creates an extra copy of every organelle. The cellular membrane squeezes together, dividing the organelles up evenly. When the two halves are squeezed completely apart, there are now two functioning cells.
These two cells are called daughter cells. During its life, a cell may divide many times. In fact, this is how you grow up. Your cells are constantly dividing, making you a little bit bigger each day!
Written by Laura McCamy