Cells are the fundamental building blocks of all living things. Every organism, from the smallest bacteria to the largest whale, is made up of cells. A typical cell has several key components that work together to maintain life. The cell membrane acts as a protective barrier, controlling what enters and exits the cell.
The nucleus is often called the control center of the cell because it contains the cell's DNA. This genetic material controls all cellular activities and contains instructions for making proteins. The nucleus is surrounded by a double membrane called the nuclear envelope, which has small openings called nuclear pores that allow materials to move in and out.
Mitochondria are known as the powerhouses of the cell because they produce most of the cell's energy in the form of ATP. They have a unique double membrane structure with the inner membrane folded into structures called cristae, which increase the surface area for energy production. Interestingly, mitochondria have their own DNA and can reproduce independently.
The endoplasmic reticulum is a vast network of membranes that extends throughout the cell. There are two types: rough ER, which is studded with ribosomes and specializes in protein synthesis, and smooth ER, which lacks ribosomes and produces lipids and other molecules. Ribosomes can also float freely in the cytoplasm, making proteins for use within the cell.