How Cells Works

HOW CELLS WORKS

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At a microscopic level, we are all composed of cells. Look at yourself in a mirror -- what you see is about 10 trillion cells divided into about 200 different types. Our muscles are made of muscle cells, our livers of liver cells, and there are even very specialized types of cells that make the enamel for our teeth or the clear lenses in our eyes!
If you want to understand how your body works, you need to understand cells. Everything from reproduction to infections to repairing a broken bone happens down at the cellular level. If you want to understand new frontiers like biotechnology and genetic engineering, you need to understand cells as well.
Anyone who reads the paper or any of the scientific magazines (Scientific American, Discover, Popular Science) is aware that genes are BIG news these days. Here are some of the terms you commonly see:
Biotechnology
Gene splicing
Human genome
Genetic engineering
Recombinant DNA
Genetic diseases
Gene therapy
DNA mutations
DNA fingerprinting or DNA profiling Gene science and genetics are rapidly changing the face of medicine, agriculture and even the legal system!
In this article, we'll delve down to the molecular level to completely understand how cells work. We'll look at the simplest cells possible: bacteria cells. By understanding how bacteria work, you can understand the basic mechanisms of all of the cells in your body. This is a fascinating topic both because of its very personal nature and the fact that it makes these news stories so much clearer and easier to understand. Also, once you understand how cells work, you will be able to answer other related questions like these:
What is a virus and how does it work at the molecular level?
What is an antibiotic and how do antibiotics work? Why don't antibiotics kill normal cells?
What is a vitamin, and why do we need to take them every day?
How do poisons work?
What does it mean to be alive, at least at the cellular level? All of these questions have obvious answers once you understand how cells work -- so let's get started!
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Enzymes

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At any given moment, all of the work being done inside any cell is being done by enzymes. If you understand enzymes, you understand cells. A bacterium like E. coli has about 1,000 different types of enzymes floating around in the cytoplasm at any given time.
Enzymes have extremely interesting properties that make them little chemical-reaction machines. The purpose of an enzyme in a cell is to allow the cell to carry out chemical reactions very quickly. These reactions allow the cell to build things or take things apart as needed. This is how a cell grows and reproduces. At the most basic level, a cell is really a little bag full of chemical reactions that are made possible by enzymes!
Enzymes are made from amino acids, and they are proteins. When an enzyme is formed, it is made by stringing together between 100 and 1,000 amino acids in a very specific and unique order. The chain of amino acids then folds into a unique shape. That shape allows the enzyme to carry out specific chemical reactions -- an enzyme acts as a very efficient catalyst for a specific chemical reaction. The enzyme speeds that reaction up tremendously.
For example, the sugar maltose is made from two glucose molecules bonded together. The enzyme maltase is shaped in such a way that it can break the bond and free the two glucose pieces. The only thing maltase can do is break maltose molecules, but it can do that very rapidly and efficiently. Other types of enzymes can put atoms and molecules together. Breaking molecules apart and putting molecules together is what enzymes do, and there is a specific enzyme for each chemical reaction needed to make the cell work properly.
You may have heard of people who are lactose intolerant, or you may suffer from this problem yourself. The problem arises because the sugar in milk -- lactose -- does not get broken into its glucose components. Therefore, it cannot be digested. The intestinal cells of lactose-intolerant people do not produce lactase, the enzyme needed to break down lactose. This problem shows how the lack of just one enzyme in the human body can lead to problems. A person who is lactose intolerant can swallow a drop of lactase prior to drinking milk and the problem is solved. Many enzyme deficiencies are not nearly so easy to fix.
Inside a bacterium there are about 1,000 types of enzymes (lactase being one of them). All of the enzymes float freely in the cytoplasm waiting for the chemical they recognize to float by. There are hundreds or millions of copies of each different type of enzyme, depending on how important a reaction is to a cell and how often the reaction is needed. These enzymes do everything from breaking glucose down for energy to building cell walls, constructing new enzymes and allowing the cell to reproduce. Enzymes do all of the work inside cells.
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