There are two main types of cells: plant cells and animal cells. They are fairly similar in structure and function, but one important difference is that plant cells have a rigid cell wall surrounding them, while animal cells do not. This article will focus on animal cells, which are the basic components of all of the tissues and organs of the human body.
While they are microscopic in size, cells are complex units that carry out critical roles in the body. Individual cells are similar to the human body in miniature, in that they contain organelles (“little organs”) that carry out functions within the cell, in the same way the organs do in the body. Here is a brief look at the parts of the cell and what they do.
Plasma Membrane- The plasma membrane or cell membrane surrounds the cell. It is a double layer made of proteins and lipids (fats), and it has many important functions, including transporting substances into and out of the cell.
Cytosol- The fluid inside the cell that contains all of the organelles.
Nucleus- The nucleus can be thought of as the “brain” of the cell. It contains the DNA, genetic material that controls cellular metabolism and contains all of the information to make new cells.
Mitochondria- Often referred to as the “powerhouse” of the cell, the function of the mitochondria is to produce ATP, a molecule that the cell uses for energy, through the process of cellular respiration.
Ribosomes- These are tiny structures that are responsible for protein synthesis. They translate the information from the genetic material into protein. Ribosomes may be free in the cytoplasm or attached to the endoplasmic reticulum.
Endoplasmic Reticulum (ER)- This organelle is actually an extensive network of thin membranes or sacs that has several functions. Endoplasmic simply means “within the cytoplasm,” and reticulum comes from a Latin word meaning “little net.” There are two types of endoplasmic reticulum: smooth and rough. Smooth ER is responsible for various activities including the synthesis of lipids, hormones and membranes, detoxification of harmful substances, and storage of calcium. Rough ER has ribosomes attached to it, and is involved in producing, storing, transporting and secreting proteins, as well as making membranes.
Golgi Apparatus- Named after an Italian scientist, the Golgi apparatus consists of a stack of flattened sacs and tubes. Proteins manufactured in the ER are transferred to the Golgi, where they are modified, stored and transported to other locations within or outside of the cell.
Lysosomes- These organelles contain enzymes that digest proteins and other macromolecules, and then release the components such as amino acids and sugars back into the cell for reuse.
Cytoskeleton- The cytoskeleton is made of thin strands of protein that support the cell and move the organelles around within the cell.
Campbell, Neil A. and Reece, Jane B. Biology, Seventh Ed. Pearson Benjamin Cummings, 2005.