What is a Protein ?

A protein is a long train of amino acids linked together. Proteins have different functions; they can provide structure (ligaments, fingernails, hair), help in digestion (stomach enzymes), aid in movement (muscles), and play a part in our ability to see (the lens of our eyes is pure crytalline protein) .

How are Proteins made ?

The process of making a protein involves various parts of a cell, the nucleus and the cytoplasm (The insides of a cell is shown in the drawing below ... the cytoplasm is everything purple and the gray area is the nucleus).

Proteins are produced from a special code found in the control center of the cell, the nucleus. The nucleus contains the codes for all the different types of proteins in a body. The nucleus contains thin strands of data, formed in a double helix, called DNA (Deoxyribonucleic Acid).

The DNA strand is made up of bases and phosphates. There are four different kinds of bases. Two are called purines (Adenine and Guanine) and two pyrimidines (Cytosine and Thymine). These four bases pair up with specific bases of the opposite type. Adenine (A) always pairs with Thymine (T) and Guanine (G) always pairs with Cytosine (C). This means that the DNA strand is complementary, with opposites matching.

When a cell receives a signal saying that a certain protein is needed, the code for producing protein is made. The double helix unwinds and one strand of the helix becomes a template for producing the protein coding template. This template is a single strand of opposite bases (from DNA) and is called RNA (Ribonucleic Acid). Bases that are floating in the cell join up with opposite bases with Uracil taking the place of Thymine. This template is called mRNA (messenger RNA), because it serves as a code messenger between DNA and protein. The process of creating a mRNA from DNA is called transcription.

There are twenty different types of Amino Acids. Each one has its own specific code, made up of three bases called a codon. This is what the RNA sequence is made of. The mRNA then travels into the cytoplasm of the cells where proteins are then synthesized. tRNA (transfer RNA) brings amino acids to the mRNA. The tRNA has a loop called the anticodon, which has the opposite sequence of letters than the mRNA, which hooks up to the mRNA at its complementary spot. Each of these tRNA can pick up a certain amino acid according to its sequence of bases. When one tRNA after another connects to the mRNA, a hydrogen bond is formed between the amino acids, forming a protein.

To view an on-line tutorial on this process take a look at the Protein Translation: Sequence of Events web site.

What does a Protein do next ?

Once a protein is made it moves a particular part of the cell where it is needed, or the cell packages it up and sends to other another cell or other parts of the body. This process is like putting groceries (proteins) in a bag at the store (the cytoplasm where they are made), taking them home (moving them somewhere else), then using them for various purposes (eggs for cooking, milk for drinking, candes for munching ...).