May 26, 2013
A Quick Refresher On Protein Synthesis
Back in high school, somewhere around 10th or 11th grade, we all learned about something called protein synthesis. However, after years of distance from those lessons and learning new information, many have forgotten about this important biological process. So, here is a brief refresher.
First of all, according to the National Institutes of Health Genetics Home Reference, “Proteins are large, complex molecules that play many critical roles in the body. They do most of the work in cells and are required for the structure, function, and regulation of the body’s tissues and organs.” Some of these cellular functions include acting as antibodies and enzymes, as well as facilitating transport and storage. In short, proteins are essential in almost every biological process that the body undertakes.
As defined by biology online, protein synthesis is the creation of proteins by cells that use DNA, RNA and various enzymes. This means that it combines data from DNA carried by RNA so that our cells can make more proteins for their various functions.
The National Institutes of Health’s National Center for Biotechnology Information explains that RNA has three roles during protein synthesis. The first of these is as the messenger RNA (mRNA), which copies the genetic information from DNA and carries it in little clusters of three-base code called codons that specify a certain amino acids. Amino acids are the basic building blocks of proteins. There are 23 basic amino acids that are linked together in different combinations to form unique proteins.
The transfer RNA (tRNA) deciphers the codon in the mRNA. The tRNA then binds and carries the amino acid to a location will it will be joined with others in a chain. Each amino acid has its own tRNA. The third RNA is ribosomal RNA (rRNA), which comes together with a set of proteins to form ribosomes. These catalyze the assembly of amino acids into protein chains and bind tRNA and the various molecules necessary for protein synthesis. These latter two are used in translation.
The website Wisc-online explains the steps of protein synthesis in 15 basic steps:
- The cell gets a message to make a certain quantity of a specific protein.
- A portion of the DNA molecule unwinds, exposing the gene responsible for that protein.
- Nucleotides and enzymes move along one strand of the exposed gene and form a molecule of mRNA. Multiple copies of mRNA are made according to the quantity of the order. They leave the nucleus and enter the cytoplasm via nuclear pores.
- An mRNA binds with a ribosome so that the mRNA can be decoded (read) by the ribosome. The message is read three nucleotide bases (triplet code or codon) at a time.
- Each codon stands for a specific amino acid. When the codon is read, an enzyme activates the corresponding amino acid.
- A tRNA molecule has two ends. One end has a specific binding cite for a particular amino acid. The other end has a particular sequence of three nucleotides, the anticodon that can base pair with a codon.
- The appropriate molecule of tRNA attaches to and carries the activated amino acid to the ribosome. Anticodon bases pair with codon in order to bring the specific amino acid to the correct place.
- A second tRNA molecule picks up another activated amino acid and brings it to the ribosome, matching anticodon to codon.
- The first tRNA releases its amino acid to the second tRNA and leaves the site. The two amino acids form a peptide bond.
- The rRNA reads the next codon. Corresponding tRNA brings the activated amino acid to the ribosome.
- The second tRNA releases its amino acids to the third tRNA and leaves the site. Amino acids link up forming peptide bonds.
- The process repeats itself until a polypeptide chain is formed.
- The polypeptide chain folds becoming a protein and is released.
- Multiple copies of the protein are made.
- The mRNA is recycled when protein production is completed.
So, the next time you wonder how our bodies make proteins, just remember redOrbit and refer to this little protein synthesis guide.
Image Credit: Andrea Danti / Shutterstock