Protein synthesis

Hi Okumu Samuel

Too much to unload here! This is a long process involving two major steps, namely transcription and translation.

Transcription

Transcription transfers the genetic code from a molecule of DNA to an intermediary molecule called ribonucleic acid (RNA). The basic nucleotide structure of RNA resembles that of DNA, but the two compounds have three critical differences. First, the structure of RNA incorporates the sugar ribose rather than deoxyribose, the sugar in DNA. Second, RNA uses the base uracil (U) instead of thymine (T). In RNA uracil binds with adenine just as thymine does in DNA. Third, RNA usually exists as a single strand, unlike the double-helix structure that normally characterizes DNA.

Transcription involves the production of a special kind of RNA known as messenger RNA (mRNA). The process begins when the two strands of a DNA molecule separate, a task directed by the enzyme RNA polymerase. After the double helix splits apart, one of the strands serves as a template, or pattern, for the formation of a complementary mRNA molecule. Free-floating individual bases within the cell bind to the bases on the DNA template using complementary base pairing. The individual bases then link together to form a strand of mRNA.

In eukaryotes (organisms whose cells have a nucleus), the mRNA strand undergoes an additional step before the next stage of protein synthesis can occur. The mRNA strand consists of coding regions called exons separated by regions called introns. The introns do not contribute to protein synthesis. Special enzymes in the nucleus remove the introns from the mRNA strand. The remaining exons then link together to form an mRNA strand that contains the entire code for making a protein.

Translation

Once transcription is complete and the genetic code has been copied onto mRNA, the genetic code must be converted into the language of proteins. That is, the information coded in the four bases found in mRNA must be translated into the instructions encoded by the 20 amino acids used in the formation of proteins. This process, called translation, takes place in cellular organelles called ribosomes. In eukaryotes, mRNA travels out of the nucleus into the cell body to attach to a ribosome. In prokaryotes (organisms without a nucleus), the ribosome clasps mRNA and starts translation before these strands have finished transcription and separated from the DNA. In both eukaryotes and prokaryotes, the ribosome acts like a workbench and clamp that holds the mRNA strand and coordinates the activity of enzymes and other molecules essential to translation.

Another form of RNA called transfer RNA (tRNA) is found in the cytoplasm of the cell. There are many different types of tRNA, and each type binds with one of the 20 amino acids used in protein formation. One end of a tRNA binds with a specific amino acid. The other end carries three bases, known as an anticodon. The tRNA with an amino acid attached travels to the ribosome where the mRNA is stationed. The anticodon of the tRNA undergoes complementary base pairing with a series of three bases on the mRNA, known as the codon. The mRNA codon codes for the type of amino acid carried by the tRNA.

A second tRNA bonds with the next codon on the mRNA. The resident tRNA transfers its amino acid to the amino acid of the incoming tRNA and then leaves the ribosome. This process continues repeatedly, with new tRNA receiving the growing chain of amino acids, known as a polypeptide chain, from a resident tRNA. The ribosome moves the mRNA strand one codon at a time, making new codons available to bind with tRNAs. The process ends when the entire sequence of mRNA has been translated. The polypeptide chain falls away from the ribosome as a newly formed protein, ready to go to work in the cell.

Protein synthesis is like building something special using instructions. Proteins are important molecules that do many jobs in our bodies. To make proteins, our cells follow a process called protein synthesis.

Protein synthesis happens in two main steps: transcription and translation. Let's imagine that our body is a big factory and our cells are the workers.

In transcription, the cell's workers, called ribonucleic acid (RNA) molecules, read the instructions for making a specific protein. These instructions are like a recipe written in a special code called deoxyribonucleic acid (DNA). The DNA is like a big library of instructions, and each protein has its own special recipe.

The RNA workers go to the DNA library and carefully copy the instructions for the protein they need to make. They create a special type of RNA called messenger RNA (mRNA), which carries the instructions from the DNA library to another part of the cell called the ribosome.

Now comes the second step, translation. The ribosome is like a factory assembly line. It takes the instructions from the mRNA and reads them to build the protein.

The ribosome reads the instructions three letters at a time. These three-letter codes are called codons. Each codon tells the ribosome which building block, called an amino acid, to add to the growing protein chain.

Imagine the ribosome as a little machine that picks up the correct amino acid and attaches it to the growing protein chain according to the codon instructions. It keeps doing this until it reaches a special codon that tells it to stop. Then, it releases the finished protein.

Once the protein is made, it folds into its proper shape, like a special origami. This shape determines the protein's function and how it will work in the body.

So, protein synthesis is like following instructions to build something amazing, just like building with LEGO blocks. Our cells use the DNA library to create mRNA, and then the ribosomes read the mRNA and build the protein by adding amino acids one by one. This process is essential for making all the proteins our bodies need to function properly.