Types of protein and their functions
Today, we are going to talk about the different types of protein and their functions.
Without any doubt, protein plays an important role in Biochemistry due to its different existing molecules and its functional diversity.
Different types of protein in the organism
Protein makes up the functional base of living beings. This is due to the fact that they participate in almost every cell chemical reaction and structure.
Therefore, proteins are extremely relevant substances among the bio-molecules that make up living beings. Above all, animal protein is one of the types of protein with best bioavailability for the human body.
This is due to its superior Essential Amino Acids profile
But regardless of their origin, we can talk about two types of protein according to their dimensional structure:
Fibril proteins have a fibrous tertiary structure whose dimension is much bigger than the other two.
In general, they perform the consolidation of tissues and some of the most important ones are:
It makes up most of the cell structures from the skin such as the epidermis, hair and nails. Moreover, its main amino acid is cysteine.
Its presence in the conjunctive tissues, specially in the cartilage, explains their resistance to being stretched.
The molecular structure of collagen is made up by triple helices, which provide elasticity and resistance to the tissues.
It has the ability to go back to its original shape after stretching.
Due to this property, it is abundant in those organs whose functioning involves expansion/retraction movements, such as the lungs, arteries or dermis.
Globular proteins, also known as spheroproteins, are different in terms of their solubility in liquids, which the fibril proteins lack.
This property is essential for the behavior of these proteins in the liquid that surrounds the cells and their organelles. In fact, it is specially important for several chemical reactions that take place in it.
For example, all enzymes belong to this group. Although we will talk about them in more depth later on.
Proteins according to their molecular structure
Their structure only consists of a peptide chain. For instance, albumin and voluminous globular proteins available in blood serum or breast milk.
On the contrary, when we talk about complex proteins we know that we are dealing with more intricate structures such as:
They are made up by a lipid fraction, which can be cholesterol, triglycerides or phospholipids, and a specific protein fraction.
Their main metabolic task consists of transporting triglycerides and cholesterol through the bloodstream.
Moreover, we can classify them depending on their lipoprotein density, which can be high, low or very low.
These proteins have long amino acid chains linked to carbohydrate structures that improve their interaction with other proteins.
Above all, these carbohydrates can be from simple monosaccharides to complex polysaccharides known as glycans.
Their importance lies in the fact that they support the exchange of ions and molecules that the cell needs with the inter-cellular medium. For example, some of them are glucose, amino acids or carbon dioxide.
Immunoglobulins or antibodies are specially relevant among glycoproteins
These substances have a high biological value due to their role in the immune system as metabolic products of lymphocytes B.
They are the elements in charge of identifying and neutralizing harmful elements like bacteria, viruses, parasites or toxins.
These are complexes made of proteins and nucleic acids present in the cell nucleus which make up the genetic material of chromosomes.
Consequently, they perform three tasks:
- Supporting the hereditary transmission mechanisms.
- Contributing to the protein synthesis.
- Helping with the mitosis or cell division process.
Some of the nucleoproteins we can list are histone proteins, present in the chromatin filament, or telomerase, which is available in the nucleus.
They have a high molecular weight and they are synthesized by the cells from the mucosa. In other words, these are the epithelial tissues that internally cover many conducts of the organism.
The most common example could be the mucin which is present in the saliva, bile or vaginal fluid
They are made up by a metal ion such as zinc, manganese, copper or iron.
Most of them are enzymes and these metals are in charge of interacting with different atoms, like oxygen, nitrogen or amino acid sulfur.
Functions of proteins
Due to the complexity of the human metabolism, we can divide all these functions in the main functional blocks. Together, they complete the repertoire of tasks performed by these substances.
Therefore, all of them are involved in one of these functions:
- Catalysis: specific enzymes are in charge of performing this task quickly and efficiently.
- Regulation, like in the case of hormones, a group of specialized hormones control certain bodily functions.
- Structure maintenance, since they provide stability and elasticity to the tissues in order to perform certain movements or to support superior structures.
- Organic defense, a task that is specifically meant for the immunoglobulins. Although there are others that are indirectly involved like fibrinogen and prothrombin.
- Substance transport through organic fluids like the blood, to where these substances have to perform their biological tasks. For example, metalloprotein, hemoglobin, which is in charge of transporting oxygen to the tissues.
- Specific reception: a common task of membrane proteins, mainly the glycoprotein group. These are able to receive signals that stimulate a specific cell task.
Finally, we also want to mention enzymes, which play a wide range of roles in our body:
Enzymes are the proteins in charge of speeding up the biochemical reactions of the metabolism, without changing their balance or the energy balance.
We can group them as:
- Oxide-reductase: they are connected to fermentation processes and breathing. In fact, they are essential for splitting glucose and producing ATP.
- Transferase: these are in charge of catalyzing the transfers of atom groups between different molecules.
- Hydrolase: they hydrolyze fat, glycogen and protein when there is water. This is also the case of chymotrypsin, trypsin and pepsin.
- Isomerase: they transform certain substances in others with the same atoms but with a different arrangement, resulting in a completely different substance.
- Lyase, capable of breaking atom links in order to produce smaller molecules.
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