Thursday, May 3, 2012

Biology 101: Cells

Cells are the basic unit of biology. All living things (except viruses, and it's debatable whether they're alive) are made of cells--or are cells themselves. Some creatures are unicellular (consisting of one cell--examples are bacteria, amoebas, and diatoms) and others are multicellular (such as plant and animals).

While the cell structure of some unicellular beings (such as bacteria) is fairly simple, the structure of the cells of protozoa, fungi, plants, and animals are very similar and very complex. When I first started learning about cell structure, I had trouble believing all those little things (called organelles) really existed.

The cell is basically a huge chemical factory, constantly busy, constantly in motion. It's filled with these organelles, such as the nucleus, the endoplasmic reticulum, the Golgi apparatus, mitochondria, and, in plants, chloroplasts.

One of the interesting things about these organelles, is where they came from; how did cells become so complex? One theory about some of the organelles--in particular, the mitochondria (the energy source for the cells) and chloroplasts (which contain the chlorophyll in plants)--is that they were originally bacteria that were taken in by cells. The mitochondria and chloroplasts even have their own separate DNA.

Besides organelles, cell have membranes that surround the cell and many of the organelles and, suprisingly (at least to me), they have their own skeleton. The membrane is particularly intriguing since it not only protects the cells (or organelles) but is also very involved in biochemical processes as well as regulating transport of materials across its boundary.

The mitochondria (and particularly the membrane of the mitochondria) and the chloroplasts are involved in two of the most important processes for all life on earth: cellular respiration and photosynthesis. I will talk about these in my next two posts.

I'm still trying to wrap my head around all this. Each of us is a walking conglomerate of millions of these cells. At this minute, they are all in action in your body. Think of it. Who you are is the sum of all these cells--the cells make up your organs and your organs make up the body you call you. All our thoughts are electrical impulses traveling through these cells. It makes me appreciate the Buddhist ideas of 'dependent origination' and having no separate, permanent self.

Quote of the Day: "Cells are the smallest living things and they have all the properties of life, including reproduction, response to environmental signals, a need for energy, and the release of waste products. ...
"All living things are made of cells. All cells are built out of the same materials and function in similar ways, showing the relationship of all life on Earth." - René Fester Kratz

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