9 junio, 2024

Cellular excretion: what it is and how it is produced

What is cell excretion?

The cell excretion It is the process by which cells expel, through their membrane, waste or toxic substances. Carbon dioxide, water, and ammonia are the waste substances that cells normally produce. However, according to the type of organism, there are additional substances, such as tannins in the case of plants, for example.

The chemical reactions that occur during this process are known as metabolism. Cellular excretion allows organisms to regulate the amount of salts or any other substance that may negatively affect their functioning. It also helps maintain your water balance.

As cellular excretion occurs?

This process can be given by:

Osmosis

During this process, the water (or waste liquid) passes through a semi-permeable membrane. The regulation or control of the levels of water and salts inside the cells is called osmoregulation.

It is also the way to control the osmotic pressure of the cell, that is, that the compounds inside the cell are neither very dissolved nor very concentrated, so that transport by osmosis can occur.

Osmoregulation reveals its importance when these three conditions are analyzed:

If the cytoplasm is hypertonic, which means that the concentration of dissolved substances is higher inside the cells than in their surroundings, then water enters the cell by osmosis and could cause it to explode if the excess is not removed in time.
If the cytoplasm is hypotonic, which is the opposite of the previous process (there is a higher concentration of dissolved substances in the extracellular environment), water will tend to leave the cell and it could become dehydrated and die if it is not replaced.
An isotonic cytoplasm, on the other hand, is one in which the dissolved substances are in the same concentration inside and outside the cell. So, the inflow and outflow of water is regular, equivalent.

It is worth saying that the cytoplasm is the living and fundamental part of the cell. In it are the nucleus, the vacuoles and other components of it.

Diffusion

It is the process of transporting the substances of the cells from the inside to the outside and vice versa, with the purpose of equalizing their magnitudes in terms of density, temperature, etc.

One can speak of simple diffusion when any place on the cell membrane is used for the substance to pass freely through it. When the participation of a protein in the process is required to dilute the substance, it is called facilitated diffusion.

Dialysis

It is the process of separating substances of different densities so that their transport through the cell membrane is possible.

These forms of cellular excretion require certain types of transport of the material to be disposed of. Depending on whether the waste goes inside or outside the cell, we talk about:

endocytosis

It occurs when a vacuole is formed with the material to be transported into the cell. There are three types: phagocytosis, pinocytosis, and receptor-mediated endocytosis.

exocytosis

In this case, it is about transporting large particles to the outside of the cell, through vesicles that fuse with the cell membrane and then open to the outside to expel the waste.

Exocytosis can be:

regulated

It occurs in cells specialized in secretion, where molecules that fulfill certain functions for the organism or that affect the physiology of other cells are released, regardless of how far or near they are within the organism.

Examples of cells in which regulated exocytosis occurs are glandular cells, hormone-producing cells, and neurons.

constitutive

It consists of the release of molecules that will form part of the extracellular matrix or will serve to regenerate the cell membrane itself. It is a process that occurs in all cells in a constant manner.

The integration between the molecules of the vesicle membrane with the plasmatic membrane occurs simultaneously with the excretion of the vesicular content that will go into the blood, interstitial fluid or certain body cavities, such as the salivary glands.

Cellular excretion and unicellular and multicellular organisms

bacteria

They are the unicellular organisms responsible for consuming, by endocytosis, those substances discarded by other living beings.

yeasts

They secrete ethyl alcohol and carbon dioxide as part of alcoholic fermentation. They also secrete B complex vitamins and a compound called ephedrine, used in many cases to treat asthma and some allergies.

multicellular fungi

Their excretion process occurs by exocytosis, since they lack excretory tissues.

Certain single-celled aquatic organisms, such as the paramecium, evolved contractile vacuoles to get rid of excess water.

What are the products of cellular excretion used for?

As stated at the beginning of this text, waste substances are generally carbon dioxide, water and ammonia, substances that are used by other organisms for certain vital processes, such as:

Aerobic bacteria, algae, and protists secrete carbon dioxide and water, necessary for photosynthesis.
Anaerobic bacteria excrete lactic acid or acetic acid, useful in making yogurt and vinegar.
Yeasts secrete ethyl alcohol, necessary in the production of liquors. They also excrete vitamins (from the B complex), necessary to care for health, as well as the antibiotics secreted by multicellular fungi.

Likewise, there are cells that transform this waste through chemical processes to obtain the energy they require to grow and self-regenerate dead tissue.

References

Secretion. Retrieved from courses.washington.edu.
cell excretion. Retrieved from emaze.com.

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