Organella is a permanent formation in the cell that performs certain functions. They are also called organelles. An organelle is what allows a cell to live. Just as animals and humans are made up of organs, so every cell is made up of organelles. They are diverse and perform all the functions that ensure the life of the cell: this is the metabolism, and their storage, and division.
What are organelles?
Organella is a complex structure. Some of them may even have their own DNA and RNA. All cells contain mitochondria, ribosomes, lysosomes, a cell center, the Golgi apparatus (complex), and the endoplasmic reticulum (reticulum). Plants also have specific cell organelles: vacuoles and plastids. Some also refer to microtubules and microfilaments as organelles.
An organelle is a ribosome, a vacuole, a cell center, and many others. Let's take a closer look at the structure and functions of organelles.
Mitochondria
These organelles provide the cell with energy - they are responsible for cellular respiration. They are found in plants, animals, and fungi. These cell organelles have two membranes: outer and inner, between which there is an intermembrane space. What is inside the shells is called the matrix. It contains variousEnzymes are substances needed to speed up chemical reactions. The inner membrane has folds - cristae. It is on them that the process of cellular respiration takes place. In addition, the matrix of mitochondria contains mitochondrial DNA (mDNA) and mRNA, as well as ribosomes, almost similar to those possessed by prokaryotic cells.
Ribosome
This organelle is responsible for the process of translation, in which protein is synthesized from individual amino acids. The structure of the organelle of the ribosome is simpler than that of mitochondria - it does not have membranes. This organoid consists of two parts (subunits) - small and large. When the ribosome is idle, they are separated, and when it begins to synthesize protein, they unite. Several ribosomes can also come together if the polypeptide chain synthesized by them is very long. This structure is called a "polyribosome".
Lysosomes
The functions of organelles of this type are reduced to the implementation of cellular digestion. Lysosomes have one membrane, inside of which there are enzymes - catalysts for chemical reactions. Sometimes these organelles not only break down nutrients, but also digest entire organelles. This can happen during a long starvation of the cell and allows it to live for some more time. Although if the nutrients still don't start flowing, the cell dies.
Cell center: structure and functions
This organelle consistsfrom two parts - centrioles. These are formations in the form of cylinders, consisting of microtubules. The cell center is a very important organelle. It is involved in the process of formation of the fission spindle. In addition, it is the center of microtubule organization.
Golgi Apparatus
This is a complex of disk-shaped membranous sacs called cisterns. The functions of this organoid are sorting, storing and converting certain substances. Mainly carbohydrates are synthesized here, which are part of the glycocalyx.
Structure and functions of the endoplasmic reticulum
This is a network of tubes and pockets surrounded by a single membrane. There are two types of endoplasmic reticulum: smooth and rough. Ribosomes are located on the surface of the latter. Smooth and rough reticulum perform different functions. The first is responsible for the synthesis of hormones, storage and conversion of carbohydrates. In addition, the rudiments of vacuoles are formed in it - organelles characteristic of plant cells. The rough endoplasmic reticulum contains ribosomes on its surface that produce a polypeptide chain from amino acids. Then it enters the endoplasmic reticulum, and here a certain secondary, tertiary and quaternary structure of the protein is formed (the chain twists in the right way).
Vacuoles
These are plant cell organelles. They have one membrane. They accumulate cell sap. The vacuole is essential for maintaining turgor. She alsoinvolved in the process of osmosis. In addition, there are contractile vacuoles. They are found mainly in single-celled organisms that live in water bodies and serve as pumps that pump excess fluid out of the cell.
Plastids: varieties, structure and functions
These are also plant cell organelles. They are of three types: leukoplasts, chromoplasts and chloroplasts. The former serve to store spare nutrients, mainly starch. Chromoplasts contain various pigments. Thanks to them, the petals of plants are multi-colored. The body needs this in the first place in order to attract pollinating insects.
Chloroplasts are the most important plastids. Most of them are found in the leaves and stems of plants. They are responsible for photosynthesis - a chain of chemical reactions during which the body receives organic substances from inorganic substances. These organelles have two membranes. The chloroplast matrix is called the stroma. It contains plastid DNA, RNA, enzymes, and starch inclusions. Chloroplasts contain thylakoids - membrane formations in the form of a coin. Inside them, photosynthesis takes place. It also contains chlorophyll, which serves as a catalyst for chemical reactions. The thylakoids of chloroplasts are combined into piles - grana. Also in the organelles are lamellae, which connect individual thylakoids and provide a connection between them.
Organelles of movement
They are typical mainly for unicellular organisms. These include flagella and cilia. The former are present in euglena, trypanosomes,chlamydomonas. Flagella are also present in animal spermatozoa. Ciliates and other unicellular organisms have cilia.
Microtubules
They provide the transport of substances, as well as the permanent shape of the cell. Some scientists do not classify microtubules as organelles.
