Surely you have heard at some point that human beings have a high percentage of water in our bodies. Or that the chemical reactions of living beings have to occur in an aqueous medium. And, as we already know, water is essential for life, as we know it, and maintaining a good level of hydration is a key element of our health.
But where is that water present in our bodies? A large part of it is inside our cells, constituting the appropriate medium for metabolic reactions to take place, giving consistency and shape to cells and containing cellular organelles, among other functions.
The structure that contains all this water in the cells and that carries out these and many other functions is what we know as cytoplasm, and in this article we explain what cytoplasm is, its function and its structure .
From we encourage you to read it if you are interested in learning about this essential structure for life.
What is cytoplasm and its characteristics
Cytoplasm is a water-based substance with a gelatinous consistency that is found inside cells, both prokaryotic and eukaryotic. It is located in the space between the plasma membrane and the cell nucleus (if it exists, since prokaryotic cells lack a nucleus).
It is one of the essential structures of every cell and is directly involved in its correct functioning, since it enables the metabolic processes necessary for life to take place.
It is mainly composed of water, ions and very diverse proteins, although lipids, carbohydrates, amino acids and nucleic acids are also found in it. Furthermore, the organelles of eukaryotic cells are embedded in the cytoplasm.
Some of its most important features are:
- It is present in all living cells . It is an essential component of cells, so no cell can lack cytoplasm and remain alive.
- It has a fluid and changing consistency , which can be more or less dense depending on the metabolic state of the cell.
- It is transparent and under the optical microscope it is seen as a fundamentally aqueous, non-refringent structure.
- We recommend you read this article, where you can learn about all the types of cells that exist.
Cytoplasm function
The cytoplasm is a structure that, because it makes up most of the cell body, participates in a large number of cell functions, among which some can be highlighted that reflect the great importance of this structure:
It enables a good part of cellular chemical reactions: all chemical reactions of living organisms must occur in an aqueous medium. This is where the cytoplasm comes in, since having an aqueous base makes it possible for numerous chemical reactions to take place, specifically the reactions of intermediate metabolism, which consists of the set of chemical processes by which some molecules are degraded and others are synthesized, providing the elements for the construction of macromolecules.
It is the medium where protein metabolism takes place , that is, the synthesis and degradation of proteins.
It contains the cellular organelles in the case of eukaryotic cells.
Supports and maintains cellular structure: since it is the environment where almost all intracellular structures are found, the cytoplasm plays a leading role in maintaining cellular structure, as well as its shape.
Enables the transport of molecules in the cell: thanks to its gelatinous composition, it makes possible the transport of molecules both within the cell itself and from its interior to the external environment and vice versa.
Participates in cellular movement. Thanks to its changing consistency, the cytoplasm is frequently involved in cell movement, as well as in the modification of cell shape for the emission of extensions or the formation of temporary invaginations.
Cytoplasm structure
The cytoplasm has a changing structure due to its fundamentally aqueous composition. Although this has not prevented different classifications of its structure from being created in its study throughout history. In this way, a division of the structure of the cytoplasm can be carried out based on its main components:
- Cytosol: corresponds to the watery part of the cytoplasm. It represents more than 50% of the total volume of the cell.
- Cytoplasmic organelles: only in the case of eukaryotic cells, since prokaryotes lack organelles. Some of them are ribosomes, lysosomes, mitochondria, chloroplasts, vacuoles, Golgi apparatus, rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER).
On the other hand, based on the location and consistency of the cytoplasm, two well-differentiated areas of the cytoplasm have traditionally been distinguished:
- Ectoplasm: corresponds to the portion of cytoplasm closest to the cell membrane, which usually has a denser and more gelatinous consistency.
- Endoplasm: this is the innermost area of the cytoplasm, which has a greater volume than the ectoplasm. It is less dense than ectoplasm and contains the organelles suspended in it.
Difference between cytosol and cytoplasm
There is often a tendency to use the concepts of cytoplasm and cytosol as synonyms to designate the same structure, but this is really a mistake, since as we will see below, they are not the same.
On the one hand, the cytoplasm is the gelatinous substance found inside all living cells, delimited by the cell membrane and the nucleus (in the case of eukaryotic cells). While the cytosol corresponds to the aqueous fraction of the cytoplasm , which makes possible the chemical reactions that take place in the cell cytoplasm, providing the aquatic medium necessary for this. Therefore, the cytoplasm comprises the cytosol plus the organelles of the cell, while the cytosol is a part of the cytoplasm.
The cytosol, in addition, always accounts for more than half of the total volume of the cell , ranging between 50 and 80% of its volume. The vast majority of its composition is water, while approximately 30% of the cytosol corresponds to molecules, which are mainly macromolecules and give it its state of colloidal suspension.
Being fundamentally a liquid, the cytosol does not have a lasting consistency or shape, but two forms can be differentiated that it can adopt , one being denser and known as a gel form, and the other having a fluid consistency and called the sol state. It is common for both forms to alternate in the cell, even in different areas of the cell, due to metabolic activity and other factors, which in many cases the cell can use to provide greater density and turgor to specific areas of its body. and thus emit extensions or carry out cellular locomotion mechanisms.