What are cellular inclusions? Cell inclusions: types, structure and functions

In addition to organelles, there are cellular inclusions in cells. They can be contained not only in the cytoplasm, but also in some organelles, such as mitochondria and plastids.

What are cellular inclusions?

These are educations that are not permanent. Unlike organoids, they are not so stable. In addition, they have a much simpler structure and perform passive functions, such as, for example, backup.

How are they built?

Most of them have a drop-shaped shape, but some may be others, for example, similar to a blob. As for the sizes, it can vary. Cellular inclusions can be as fewer organelles as they are in size or even larger.

They consist mainly of one particular substance, in most cases organic. It can be either fat, carbohydrate or protein.

Classification

Depending on where the substance from which they are made comes from, the following types of cellular inclusions exist:

• Exogenous;
• Endogenous;
• Virus.

Exogenous cellular inclusions are constructed from chemical compounds that entered the cell from the outside. The same ones that are formed from the substances produced by the cell itself are called endogenous. Virus inclusions though are synthesized by the cell, however it occurs as a result of hit of DNA of a virus in it. The cell simply takes it for its DNA and synthesizes the protein of the virus from it.

Depending on the functions performed by cellular inclusions, they are divided into pigmentary, secretory and trophic.

Further inclusions are divided into species depending on the specific chemical compounds from which they are composed.

Cell Inclusions: Functions

They can have three functions. Let's consider them in the table

These are all functions of non-permanent formations in the cage.

Inclusion of animal cells

The cytoplasm of the animal contains both trophic and pigment inclusions. In some cells there are also secretory ones.

Trophic in the cells of animals are inclusions of glycogen . They have a granule shape about 70 nm in size.

Glycogen is the main reserve substance of the animal. In the form of this substance, the body stores glucose. There are two hormones that regulate glucose and glucose metabolism: insulin and glucagon. They are both produced by the pancreas. Insulin is responsible for the formation of glycogen from glucose, and glucagon, on the contrary, is involved in the synthesis of glucose.

Most of the inclusions of glycogen are found in the liver cells. They are also present in a large number in the muscles, including the heart. The glycogen inclusions of liver cells are in the form of granules about 70 nm in size. They gather in small bunches. Glikogenovye inclusions of myocytes (muscle cells) have a rounded shape. They are single, with a bit more ribosomes.

Also for animal cells, lipid inclusions are characteristic. These are also trophic inclusions, thanks to which the body can receive energy in an emergency. They consist of fats and have a drop-shaped shape. Basically, such inclusions are found in fatty connective tissue cells - lipocytes. There are two types of adipose tissue: white and brown. White lipocytes contain one large drop of fat, brown cells - numerous small ones.

With regard to pigment inclusions, for animal cells, those that are composed of melanin are characteristic. Due to this substance, the iris of the eye, skin and other parts of the body have a certain color. The more melanin inclusions in cells, the darker is that of these cells.

Another pigment, which can be contained in animal cells, is lipofuscin. This substance is yellow-brown in color. It accumulates in the heart muscle and liver as the organs grow older.

Inclusion of plant cells

Cellular inclusions, the structure and functions of which we are considering, are also contained in plant cells.

The main trophic inclusions in these organisms are starch grains . In their form, plants store glucose. Typically, starch inclusions have a lenticular, spherical or ovoid shape. Their size may vary depending on the type of plant and the organ in the cells of which they are contained. It can be from 2 to 100 μm.

Lipid inclusions are also characteristic of plant cells. They are the second most common trophic inclusions. They have a spherical shape and a thin membrane. They are sometimes called spherosomes.

Protein inclusions are present only in plant cells, they are not characteristic of animals. They consist of simple proteins - proteins. Protein inclusions are of two types: aleurone grains and protein bodies. Aleyron grains can contain either crystals or simply amorphous protein. Thus, the former are called complex, and the latter are called simple. Simple aleurone grains, which consist of amorphous protein, are less common.

As for pigment inclusions, plants are characterized by plastoglobules . They accumulate carotenoids. Such inclusions are characteristic of plastids.

Cellular inclusions whose structure and functions we consider are mostly composed of organic chemical compounds, but in plant cells there are also those that are formed from inorganic substances. These are crystals of calcium oxalate.

They are present only in cell vacuoles. These crystals can be of the most diverse form, and often it is individual for certain plant species.