The Basics of a Cell

Think of the contents of a cell as a liquid. To help you imagine it, let's compare it to a special type of soup. Unless the soup is in a bowl or a Ziploc bag, it just dribbles everywhere. A cell, although obviously not contained in a bowl or a bag, does have a membrane surrounding it to keep it together. Within most cells is a nucleus which has its own membrane around it to keep its contents separate from the rest of the cell. A number of other “organelles” exist within a cell, each of these bound by their own respective membranes. These organelles have special jobs which are responsible for keeping the cell alive. Most importantly, to our understanding of cancer, is the DNA within the nucleus of the cell. Therefore, DNA is the component we will focus our attention on.

The Chain of Command
We can think of the DNA as the executive of a large corporation; it really doesn’t do a whole lot other than boss everyone else around. The boss (or DNA) has messengers who send out the instructions to the workers. In the case of a cell, the DNA “tells” the messengers what it needs done. In the molecular world, the messengers are actually strands of RNA, conveniently called messenger RNA. The RNA makes the right proteins for the job and the proteins complete the physical labor. In a sense, the proteins are the workers.

What we've just covered is a major theory in biology. To simplify it, DNA produces RNA, which in turn produces proteins. To understand exactly what this means, each of the three key pieces (DNA, RNA and proteins) will be broken down and briefly discussed individually.

DNA
All the information about us is stored within DNA strands. Just as a computer stores its information in electronic chips - in living beings, the information is kept within DNA. Electronic chips store the database of a computer while humans store their “database” within the twenty-six pairs of chromosomes. These chromosomes consist of double stranded DNA; packaged in a neat and organized manner as opposed to a big, waded up mess.

To help us categorize this molecular world, science has segmented the chromosomal DNA into many smaller sections called genes. But in reality a piece of DNA is all one long strand.

Several different molecules make-up the DNA strand, but the most essential to this discussion are the “base pairs”. There are four base pairs, which may also be called nucleotides. These are; adenine, guanine, thymidine and cytosine (you may have seen them written as A, G, T and C). The four “base pairs” are strung together to make up a single DNA strand. It is their alternating sequence that forms the DNA code. For example, a piece of the strand might be designated by the following: AAAGTTAC... Although it just seems like randomness, incredibly, this code makes us exactly who we are.

In illustrations, DNA is usually drawn as two threadlike strands twisted around one another, giving it a helical form. However, it is probably really only like this during cell division. The rest of the time, the DNA strands are wrapped up in a super coiled, balled up form. They unwind to become a double helix when the DNA is being copied. At different places on the DNA strand are the start and end regions for reading the code. As the DNA untwines itself during the cell’s division, the regions that were once hidden become exposed. A special protein can then attach itself at a start site and “read” the sequence until it reaches the end site. This protein makes a separate strand known as RNA (the messenger) from the original DNA template.

RNA
Next, the messenger RNA creates a protein. The RNA also has a start and a stop site. Between the start and stop sites are a long stretch of base pairs. It is this series of base pairs that contain the genetic instructions which will eventually create a specific protein. The new protein is created when other proteins bring in amino acids (the building blocks of a protein) and link them together in the right order based on the RNA sequence.

Proteins
Once an entire strand of amino acids has been created and linked together in the right sequence, a protein has been formed.

AS we mentioned earlier, proteins are the workers. They are responsible for making the necessary cellular events happen. As you can see from our discussion above, it takes proteins to make proteins. They make things happen.

Some proteins function as enzymes. These speed up the events occurring within the cell. Without enzymes, the cell could not maintain itself. The cell is dependent on these activities for its survival. Our bodies as a whole require certain events to take place; important things like breathing, eating, exercise, etc. Cells must fulfill similar requirements or they will die.

Cellular activities are commonly called metabolism. Cells take in "raw" compounds and then must break them down into a usable form. This act cannot happen without functioning proteins.

Proteins are also required for cell division. Without functioning proteins, the cell will not divide properly or it may not even divide at all. The membrane around a cell and its organelles is composed in part by proteins also. Cells transmit a variety of signals, some within themselves and others to nearby cells. These signals are all actually proteins that signal a particular event to take place.

As you can see, proteins play a vital role in all cellular activities.