Plant cell: what it is, structure and functions

In this article you will know a little more about the plant cells , what they are, what their structure and main functions . See this and more!

Animal and plant cells are formed by three fundamental regions: plasma membrane, cytoplasm and nucleus. The membrane is responsible for enveloping all the components of the cell, separating the external medium from the inner.

In addition, it is semipermeable, that is, it allows the exchange of substances between the cell and the medium. By filling the cell, we will find a material of viscous consistency, called cytoplasm . It is in the cytoplasm that the vital functions of the cell occur, such as: digestion, respiration, transport, etc. The cellular organelles are immersed in this cytoplasm.

The main organelles of plant cells are: ribosomes, endoplasmic reticulum, Golgi complex, mitochondria, lysosomes, centrioles and peroxisomes. Plant cells have all these organelles as well, however, centrioles are found only in bryophytes and pteridophytes. In addition to these organelles, plant cells have vacuoles and plastids. A unique structure of plant cells is the presence of a cell wall, which protects the cell against the entry of microorganisms and prevents cytolysis (cell death due to water entry).

Structure of the plant cell

As we have seen, the plant cell has a shell outside the cell membrane, called the cell wall. The cytoplasm of the plant cell presents large vacuoles : cavities limited by membranes, containing in the interior the vacuolar juice with reserves of water and other substances. Also found are plasters, whose function is to store substances such as starch or pigments, such as chloroplasts, which store green pigment called chlorophyll, responsible for photosynthesis.

Functions of organelles

Ribosomes

The ribosomes participate in the process of protein synthesis . They are structures formed by two rounded parts, with different sizes, which are arranged one above the other. These structures are basically composed of proteins and a type of ribonucleic acid: ribosomal RNA (rRNA).

Centuries

They are not found in all plant cells, only in some. In cells that do not have centrioles, such as pines and angiosperms, there is, however, the centrosome. From this region the microtubules of the cytoskeleton depart. Each centriole is a cylindrical structure, composed of nine groups of three protein microtubules.

Peroxisomes

Peroxisomes are round-shaped membranous organelles whose main function is the oxidation in the presence of oxygen gas of certain organic substances in cells, especially fatty acids. Although it is a beneficial process for cells, the formation of a very toxic by-product occurs: hydrogen peroxide (H2O2, hydrogen peroxide). As it is extremely toxic, this compound should be rapidly degraded. Its decomposition is made by an enzyme contained in the peroxisomes, called catalase, giving rise to water and oxygen.

Peroxisomes can also act in the detoxification of the organism in relation to certain substances, like the ethanol, present in alcoholic beverages. In this case, peroxisomes are the liver cells that act because they contain enzymes capable of breaking ethanol, giving rise to less toxic products. About 25% of ingested alcohol is degraded by peroxisomes. The remainder is degraded by the non-granular (agranular or smooth) endoplasmic reticulum. The various enzymes contained in the peroxisomes are produced by free ribosomes in the cytosol and incorporated into them.

In plants, leaf cells and germinated seeds have differentiated peroxisomes, known as glyoxysomes. In leaf cells, these structures act in some reactions of the photosynthesis process , related to the fixation of carbon dioxide.

Endoplasmic reticulum

The endoplasmic reticulum is composed of channels delimited by membranes. These channels communicate with the nuclear envelope. The endoplasmic reticulum can be considered a distribution network, taking the material from any point to the point of use. The endoplasmic reticulum plays an important role in the transport of substances within the cell . It can be of two types: non-granular (smooth or agranular) and granular (granular or rough).

The non-granular endoplasmic reticulum has more cylindrical tubule systems and no membrane-bound ribosomes. It mainly participates in the synthesis of steroids, phospholipids and other lipids, such as cholesterol.

The granular endoplasmic reticulum has flat tubule systems and ribosomes attached to the membrane facing the cytosol, which gives it granular appearance. The main function of this reticulum is the synthesis of proteins, which may or may not be sent to the exterior of the cells. This reticulum is also called ergastoplasma, which means to elaborate, to synthesize.

Golgi Complex

The Golgi complex is usually located near the nucleus and granular endoplasmic reticulum and is composed of several sets of lamelliform saccules (cisterns), which form a variable number of cells. Each cell receives the name of dictiosomo or golgiossomo. Like the granular endoplasmic reticulum, the Golgi complex is more abundant in animal cells with secretory function. Its function, however, is not linked to the production of protein secretions, but to the concentration, modification and elimination of these secretions.

Lysosomes

Lysosomes are small rounded membranous vesicles that contain large amounts of enzymes responsible for intracellular digestion . Because of this, the lysosomes are linked to the heterophasic and autophagic functions.

Mitochondria

Mitochondria are organelles responsible for aerobic cellular respiration . In general, the mitochondria is shaped like a rod. It is formed by two lipoprotein membranes: one external, smooth and one internal, which presents invaginations, forming mitochondrial ridges.

Plastos

Plastos are structures found only in plant cells and some protists, and can be classified into three types: chromoplasts, leucoplasts and chloroplasts.

Chromoplasts : Carotenoids are pigments, but not chlorophylls. They do not take photosynthesis and are responsible for the yellowish, orange and reddish coloration of flowers, old leaves, some fruits and roots.

Leucoplasts : are colorless as they do not contain pigments. Some store starch (amyloplasts), others store oils and proteins.

Chloroplasts contain chlorophyll and carotenoid pigments. Chloroplasts are important organelles that participate in the process of photosynthesis. There are chloroplasts of various forms and in varying numbers per cell. The chloroplasts of plant cells, when examined in sections under the electron microscope, are formed by three main components: the envelope, the thylakoids and the stroma.

Cell juice juice

Also called the central vacuole , this organelle is delimited by a lipoprotein membrane called tonoplast. It is unique to plant cells and certain algae and fungi. In young plant cells, the vacuoles are numerous and small and, as the cell grows, they fuse into a single, large, well-developed central vacuole.

Inside there is an aqueous solution of various substances, such as salts, carbohydrates and proteins. Vacuoles are important in osmotic phenomena, and when they contain pigments such as anthocyanins, they are primarily responsible for the blue, violet, red and purple coloration of flowers and leaves. They also act similarly to the lysosomes of animal cells in the autophagy process.