Protein synthesis

Protein synthesis

Protein synthesis is a fascinating process that takes place in each cell of your body hundreds of times per second. Considering how incredible this process is, it’s worth knowing how it happens

If you are a sportsperson and eat a diet rich in proteins, it’s definitely worth reading this in order to understand how your body incorporates and converts protein into useful substances to help keep it running.

It is, without a doubt an exciting mechanism

What is protein synthesis?

protein synthesis is, without a doubt, one of the most important biological processes that take place not just in the human body but in all of the animals that inhabit the planet.

Put simply, this mechanism is the way that our bodies create all the specific protein needed after obtaining it from food, bearing in mind that these different types of protein are present in different quantities in almost all types of food. It plays an important role in both in Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)

The process called protein synthesis starts in the nucleus of cells, specifically, in the ribosomes located in the cell’s cytoplasm.

Functions synthesis how they act

Before this happens, while food is still in the digestion stage, the body breaks down peptide bonds that join together aminoacids that make up part of a protein so that it can be subsequently used with the objective of creating its own structures.

There are twenty essential amino acids and during the course of this process, the DNA is transcribed into RNA.

The importance of protein synthesis

The functioning of cells is mainly based on protein.
It’s important to remember that the function of each protein is defined according to its molecular structure, it’s location inside the cell it forms a part of and its participation in a determined biological process.

Accordingly, we can specify that this is the way in which a clear and precise classification can be made.

The role of each protein is also defined by its exact composition and structure, which end up being stored in the DNA. The process known as protein synthesis presents itself to stabilise an imbalance caused by the loss of cellular proteins when they try to do their original function.

These facts allow us to understand that through our diet and this mechanism the organism replaces protein lost while carrying out its vital processes

What’s the purpose of protein synthesis?

Protein synthesis allows the body to form the necessary macromolecules to carry out its functions.

The human body isn’t capable of using digested proteins which come directly from food in their whole form but needs to break its peptide bonds and create new structures from the amino acids they contain.

The purpose of protein synthesis

In general terms, it can be said that the purpose of protein synthesis is to create the following types of protein:

  1. Enzymes. Enzymes are proteins whose principal function is to act as catalysts, meaning that they accelerate biochemical reactions produced by the body. Without a shadow of a doubt, the most known enzymes are those that intervene in the digestion process of foods. From this group, it’s important to mention amylase, which is present in the saliva of all mammals and breaks down the starch content of sugars. Pepsin and trypsin break down large protein-based molecules in shorter polypeptides with the goal of crossing the lining of the small intestine.
  2. Hormones. Hormones are proteins with the ability to transmit signals from place to another. For example, insulin is an extracellular protein whose purpose is to regulate glucose breakdown and stabilise blood sugar levels.
  3. Contractile proteins are the proteins that make the occurrence of muscular movement possible. Actin and myosin are the best known.
  4. Structural proteins. Tend to have a filamentous appearance and their role is to provide support. An example would be keratin, which is a macromolecule that strengthens the protective layer on hair and nails. In the same way collagen and elasticin are an essential part of connective tissue, which the body uses to construct tendons and ligaments for the joints.
  5. Carrier proteins. They act as vehicles for a wide range of cellular processes, taking fundamental ions, small molecules and even other types of protein-based macromolecules of a smaller size. The majority of carrier proteins act inside the tissues corresponding to the biological membrane.
  6. Antibodies. These are proteins that carry out their activity inside the immune system. In fact, their principal function is to destroy external microorganisms that invade the body and can cause damage and negative health consequences. As a rule of thumb, antibodies anchor themselves to the membranes of white blood cells or segregate themselves from the extracellular matrix .

Importance of genetic code for protein synthesis

The coded information found inside our DNA (genotype) expresses itself through various functions carried out by proteins and other chemical reactions catalysed by enzymes.
Despite being very compact, the genetic material coded inside the nucleus (in the form of DNA) is enormous and this inhibits it from getting through the cellular membrane. For this reason, it must be copied by RNA, which has smaller chains, through the transcription process.
This RNA moves around the exterior of the nucleus until the ribosomes are located in the cytoplasm and rough endoplasmic reticulum with the purpose of directing the assembly of proteins.

This process confirms the theory that protein does not take its form from our genes. What really happens is that the RNA provides exact information through protein synthesis generating one of the types

Where does protein synthesis take place?

Generally speaking, we can confirm that this process happens in the cytoplasm, although it is also true that it isn’t literally there. It’s important to take into account that there is a small difference in terms of the actual location where the synthesis takes place in eukaryote and prokaryote cells.

Ribosome is the machinery responsible for ensuring protein synthesis is carried out.

The correct functioning of subunits in conjunction with the constant supply of residual amino acids transported by RNA (referred to hereafter as RNAt) determines the length of each protein chain, and ultimately, the completion of the synthesis of these macromolecules
Where proteins are synthesised

Where does protein synthesis take place in prokaryote cells?

The absence of a nucleus and a low level of compartmentalisation in cells are two principal characteristics that differentiate prokaryote and eukaryote cells.
Furthermore, in the case of prokaryote cells, ribosome is found dispersed in the entire cytoplasm, which is why it is stated that in this case, protein synthesis takes place in the cytoplasm.

Where does protein synthesis take place in eukaryote cells?

In eukaryote cells, ribosomes are also found in the cytoplasm, although it is true that they can also be found in the endoplasmic reticulum (hereafter known as ER) The ER membranes form a complex, continuous network while forming a membrane outside of the nucleus and a plasmic membrane.

The ER membranes of each cell have very slight differences between them and their size and structure are determined by their particular function.

For example, those cells that are implicated in the synthesis of large volumes of protein need a much bigger ER network compared with those that don’t deal with these volumes.

There are two types of ER: smooth and rough. The exterior surface of rough ER is called cytosol and is covered by ribosomes, while smooth ER completely lacks ribosomes.

Does protein synthesis happen in rough ER?

Let’s take another look at ribosomes. Both the smooth and rough varieties translate messenger RNA (hereafter known as mRNA) into polypeptide sequences.
The place where protein synthesis occurs is determined by the possible post-translational modifications Proteins that target the ER often contain a specific sequence, which is called a signal.

This signal sequence is synthesised at the beginning of the translation, and once formed, it moves towards the rough ER. The ribosomes that have this type of mRNA together with the partially synthesised proteins attach to the ER, the place where the protein synthesis is completed, and this results in complete proteins.
Once the translation is completed, the proteins are released into the ER channels and continue the protein secretion process

Does protein synthesis take place in the mitochondria?

You probably already know that mitochondria also contain ribosomes, and for that reason, are involved in the process of protein synthesis of 13 coded genes for the mitochondrial chromosome.

Some recent studies have shown that some coded proteins inside the nucleus are also synthesised on the surface of the mitochondria

Protein synthesis mitochondria

And lastly… Where does protein synthesis take place?

From what we have reported in this article, it seems that answering the question of where protein synthesis takes place is not as simple as it might seem at first since, as several scientific studies have shown, this process takes place in a wide range of places.

The only thing that seems evident is that protein synthesis takes place in all parts of cells that contain ribosomes because, to sum up, these are the ‘machinery’ responsible for the process actually happening.

This means that protein synthesis occurs in the cytoplasm, in the upper part of the rough ER, in the mitochondria and in the mitochondrial membrane

It is also clear that protein synthesis takes place neither in the nucleus nor in the nucleolus. And, since proteins are macromolecules, it is not possible for them to pass through the membrane that surrounds the nucleus

Conclusions

Summing up, we hope that we have achieved our goal of helping you understand what the synthesis process involves which allows your body to transform the proteins that you eat through food into vital elements for its functioning.

Just think, that once this mechanism has been carried out, your body to regenerate your tissues or provide a defense against external, invading microorganisms, just to give one example

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