Vacuoles

In general, vacuoles are very simple structures , variable in number and shape, made up of a membrane and an internal content made up mainly of water and amino acids . Due to their great digestive activity , they are compared to the organelles of animal cells, the lysosomes.

Definition

It is defined as each of the small cavities in the cytoplasm of a cell or in the tissue of an organism, delimited by a membrane and filled with air or fluid, which perform various functions.

The fusion of various vesicles allows the development of vacuoles, the vacuoles are formed from the integration of numerous membranous vesicles, until they acquire a shape according to the needs of the cell in question.

Source

This word comes from the Latin “vacuus” which means “empty” , which was translated into Spanish as vacuole. It first emerged in France in the 18th century, thanks to the French biologist and botanist Félix Dujardin.

Vacuoles have long been considered to form from the endoplasmic reticulum. Since these are very similar to the  lysosomes  of animal cells, it was therefore concluded that the vacuoles of at least some plant cells have a similar origin to that of animal lysosomes.

The formation of lysosomes is associated with a highly specialized region of the cytoplasm. These are founded from the rough endoplasmic reticulum and later the enzymes are packaged by the Golgi complex. This association of membranes has also been found in some plant cells, so the origin of the vacuoles could be the same as that of animal lysosomes.

Characteristics of vacuoles

Some of the most striking characteristics of vacuoles are the following:

• They capture and store water, allowing the growth of plants with very little waste of material.
• Inside it is a fluid substance of variable composition called vacuolar juice.
• Pigments are concentrated  .
• They are variable in size, which means that they can occupy from 5% to 90% of what is the cell volume.
• They are surrounded by a simple membrane that responds to the name of tonoplast .
• Vacuoles are made primarily of water and amino acids.
• They are found mainly in the cells of plants and fungi.
• They do not have a specific shape.
• In plants they fulfill similar functions to  lysosomes  in animal cells, since both are sacs that contain digestive enzymes.

Types

Pulsating vacuoles

These are responsible for extracting water from the cytoplasm and expelling it through the process of osmosis, also known as passive transport.

Digestive vacuoles

As their name indicates, they are responsible for activating the digestive process of nutritional substances and the elimination of waste outside the cell.

Food vacuoles

They act directly on the nutritional function. These are formed from the cell membrane or the endoplasmic reticulum.

Function of vacuoles

Some of the functions that vacuoles fulfill are as follows:

• Disintegration of macromolecules and the recycling of their components within the cell.
• They are capable of storing soluble proteins and pigments such as anthocyanins, which are responsible for many colors in flowers and plants.
• They contribute to the hydration of the cell and give strength to its tissue.
• They reserve sugars and proteins.
• They discard crystals and tannins, among others.
• Regulates the osmotic properties of the cell
• Helps maintain pressure within the cell (turgor).
• Maintains the pH balance within the cell.
• Exports products out of the cell.
• Degradation of molecules.

Structure

It has a large definition, this includes  a variety of sacks attached to the membrane . Membranes are made up of  phospholipids , but each organism may use slightly different phospholipids. Embedded in the membranes are  proteins that can function to  transport molecules across the membrane  or to give it structure. Various combinations of these proteins allow different vacuoles to handle and maintain different materials.

In each organism, different genes cause different proteins to embed themselves in the membrane of the vacuole. This allows different molecules to pass through and gives vacuoles  different properties . Most plant cells have evolved to use vacuoles as water storage organelles , which provide a variety of functions to the cell.

Location

Vacuoles are present in all plant cells. It also appears in some prokaryotic and eukaryotic cells. They are regions surrounded by a vacuolar membrane and filled with a liquid called cellular juice.

It occupies 90% of a cell when it is mature, reducing the  cytoplasm  to a very narrow layer pressed against the cell wall.

Chemical composition of vacuoles

The content of the vacuoles is highly variable . It depends on the plant, the cell and the physiological state of the cell. In addition, there are compounds that are permanently stored in the vacuole and others that are periodically exchanged with the cytoplasm. It can be found:

• Ions (K, Mg, Ca, Cl),
• Organic acids: Proteins, mucilages, heterosides
• Oxalic acid: It is stored in the form of calcium oxalate
• Malic acid.
• Carbohydrates: It is stored in a soluble form, these are sucrose and inulin.
• Proteins: These are glycoproteins.

Importance

Vacuoles constitute a kind of  storehouse for substances that are needed for the life and growth of the plant cell. It also works as a filter for substances harmful to the body such as nicotine, heavy metals and herbicides.