The Human Cell

The human body is made up of trillions and trillions of cells. A cell is the smallest living unit known, and is often called the “building block” of the body. This is because cells make up everything in the body. There are bone cells, and blood cells, and heart cells, and skin cells, and hair cells, and brain cells, and so many, many more. Each of these cells functions a bit differently, but their overall purpose is to keep the body functioning, growing, and developing properly. Each cell also has its own particular structure, but there are some general characteristics that are found in most cells.

A cell is completely contained within a plasma membrane. This membrane keeps all of the cell's contents neatly inside, while keeping out harmful substances. Inside the cell are the cytoplasm, the nucleus, and the organelles. The cytoplasm is a gel-like substance in which the nucleus and organelles are found. The nucleus is the “brain” of the cell. It contains the genetic information in the form of chromosomes, as well as the nucleolus, a structure that helps the nucleus function. The nucleus is completely separated from the rest of the cell by a membrane similar to the plasma membrane that encircles the cell.

Each of the organelles has a different function, but they all work to keep the cell healthy and help it perform its job. Some common organelles can be found in the diagram below. They are all important, but for the purposes of genetics, the most important are the ribosomes. Ribosomes are crucial to the creation of proteins, which carry out the functions of the genes. Ribosomes can be found free-floating in the cytoplasm, or attached to an organelle called the endoplasmic reticulum (ER). Mitochondria are also important, as they have their own DNA and genes separate from the genes on chromosomes found in the nucleus.