Non-membrane organoids: structure and functions

All cells of living organisms consist of a plasma membrane, nucleus and cytoplasm. Organoids and inclusions are found in the latter. Organoids are permanent formations in a cage, each of which performs certain functions. Inclusions are temporary structures that mainly consist of glycogen in animals and starch in plants. They perform a backup function. Inclusions can be found both in the cytoplasm and in the matrix of individual organelles, such as chloroplasts.

Classification of organelles

Depending on the structure, they are divided into two large groups. In cytology, membrane and non-membrane organoids are isolated. The first can be divided into two subgroups: one-membrane and two-membrane.

Single-membrane organoids include the endoplasmic reticulum (reticulum), Golgi apparatus, lysosomes, vacuoles, vesicles, melanosomes.

Mitochondria and plastids (chloroplasts, chromoplasts, leukoplasts) are reckoned as two-membrane organoids . They have the most complex structure, and not only due to the presence of two membranes. In their composition, inclusions and even whole organoids and DNA can also be present. For example, in the mitochondrial matrix, ribosomes and mitochondrial DNA (mtDNA) can be observed.

Non-membrane organelles include ribosomes, a cell center (centriole), microtubules and microfilaments.

Nemembrannye organoids: functions

Ribosomes are needed in order to synthesize a protein. They are responsible for the translation process, that is, the decoding of information that is on the mRNA, and the formation of a polypeptide chain of individual amino acids.

The cell center participates in the formation of the spindle of division. It is formed both in the process of meiosis, and mitosis.

Such non-membrane organelles, like microtubules, form a cytoskeleton. It performs structural and transport functions. On the surface of microtubules, both individual substances and whole organoids can move, for example, mitochondria. The process of transportation occurs with the help of special proteins, which are called motor proteins. The center of organization of microtubules is the centriole.

Microfilaments can participate in the process of changing the shape of the cell, and also are needed for the movement of certain unicellular organisms, such as amoeba. In addition, various structures can be formed from them, the functions of which have not been fully studied.

Structure

As is clear from the title, organoids of a membrane-free structure do not have membranes. They consist of proteins. Some of them also contain nucleic acids.

The structure of the ribosomes

These non-membrane organoids are located on the walls of the endoplasmic reticulum. The ribosome has a spherical shape, its diameter is 100-200 angstroms. These non-membrane organoids consist of two parts (subunits) - small and large. When the ribosome does not function, they are separated. In order for them to unite, there must be the presence of magnesium or calcium ions in the cytoplasm.

Sometimes, when synthesizing large protein molecules, ribosomes can be combined into groups called polyribosomes or polysomes. The number of ribosomes in them can range from 4-5 to 70-80 depending on the size of the protein molecule that they synthesize.

Ribosomes consist of proteins and rRNA (ribosomal ribonucleic acid), as well as water molecules and metal ions (magnesium or calcium).

Structure of the cell center

In eukaryotes these non-membrane organelles are composed of two parts called centrosomes, and the centrosphere is the lighter area of the cytoplasm that surrounds the centrioles. Unlike the case with ribosomes, parts of this organoid are usually combined. The totality of the two centrosomes is called the diplomatism.

Each centrosome consists of microtubules, which are twisted in the form of a cylinder.

Structure of microfilaments and microtubules

The first consist of actin and other contractile proteins, such as myosin, tropomyosin, etc.

Microtubules represent long cylinders, empty inside, which grow from the centriole to the edges of the cell. Their diameter is 25 nm, and the length can be from several nanometers to several millimeters, depending on the size and functions of the cell. These non-membrane organoids consist primarily of tubulin protein.

Microtubules are unstable organoids, which are constantly changing. They have a plus-end and a minus-end. The first constantly adds to itself molecules of tubulin, and from the second they are constantly split off.

Formation of non-membrane organoids

The nucleolus is responsible for the formation of the ribosomes. It produces a ribosomal RNA, the structure of which is encoded by ribosomal DNA, located on special sections of chromosomes. The proteins that make up these organoids are synthesized in the cytoplasm. After that, they are transported to the nucleolus, where they combine with the ribosomal RNA, forming a small and large subunit. Then the finished organoids are moved to the cytoplasm, and then to the walls of the granular endoplasmic reticulum.

The cell center has been present in the cell since its inception. It is formed by dividing the maternal cell.

Conclusion

As an output, we give a brief table.

So, now you know all about the non-membrane organoids that are found in both plant and animal and fungal cells.