The Animal Cell - A Tour Through Organelles

The animal cell is a complex machine, with many parts working in cohesion to sustain life. If you ask any biologist, they're sure to tell you that a working knowledge of the cell is absolutely essential for most anyone. While this may be somewhat overblown, knowing where one comes from is never a bad thing. In any basic discussion of the cells, a good method of division involves separating the cell into its component organelles. The organelles in a cell work in a similar method as organs do in the human body: each one performs a specific function which allows the whole to live.

The first organelle which happens to come up in most textbooks concerning the animal cell is the nucleus, and why not? It's the organelle which most people are familiar with, the "control center" and "brain" of the cell. In its membrane, the genetic material is stored as tightly coiled DNA, locked up by histone proteins until the time is right. The nucleus will relax these histones in the event that a protein must be synthesized, and event which is as common as it is important. In protein synthesis, histones are relaxed as other proteins help to construct complementary RNA, which will be used outside of the nucleus to produce protein. The nucleus also contains families of protein which function in repairing DNA which has been damaged, a surprisingly common occurrence.

The endoplasmic reticulum, or ER, helps to connect the functions of the nucleus with the rest of the cell. It consists of a membrane which is continuous with that of the nucleus and extends outward into the cell. There are two distinct types of endoplasmic reticulum: the rough ER and the smooth ER. The rough ER functions in protein synthesis. Its name comes from its ribosome-studded surface. These ribosomes, organelles in their own right, are used in protein synthesis as a sort of area of assembly. Their production is the task of the nucleolus, a small organelle located within the nucleus, but their destination is the rough ER. The smooth ER conducts a task which is just as important. It is the chief organelle in production of lipids. Lipids, better known as fatty molecules, compose the cellular membrane, as well as any other carrier membrane within the cell. Because these cells have an important connection to membrane synthesis, they also process proteins which will eventually be anchored on the cell membrane.

If the nucleus is the central office of a cell, the golgi apparatus is the shipping and packaging division. The endoplasmic reticulum buds off small blobs of membrane called vesicles. These make their way to the golgi apparatus, where they are taken in, reprocessed, and redirected for transport all over the cell. The golgi apparatus also creates lysosomes, small bubbles of membrane which contain protein that is used in the destruction of unneeded cell parts.

The mitochondrion is the power plant of the cell. Most of the activities of a cell need some sort of energy input to occur. This input usually takes the form of ATP, adenine tri-phosphate. The mitochondrion's membrane is specially constructed to allow for the creation of a large quantity of ATP for cellular activity. Unlike the other organelles, the mitochondria have their own genome with gene sequences necessary for producing the proteins which will later perform roles in cellular energy production.

While this list of cell organelles is nowhere near exhaustive, it's a good primer. There are many, many more organelles in the cell to be explored, each with its own function, each incredibly valuable to the processes of life.