THE LYSOSOMAS
The lysosomes are vesicles of about one micron in diameter, filled with lytic enzymes for various organic substances (lysozyme, ribonuclease, protease, etc.) Lysosomes have the function of isolating these enzymes from the rest of the cell, which would otherwise be attacked and demolished.
The lysosomes therefore serve the cell to digest foreign particles. Depending on the nature and size of the substances incorporated by the cell, the process is called pinocytosis (when it comes to droplets), or phagocytosis (when it comes to more or less large particles). After the usable fractions have been reabsorbed by the cell, the residue to be eliminated is transported to the surface outside the cell. Lysosomes can be considered as the internal digestive system of the cell, and can have two main modes of action. First, in single-celled organisms such as paramecis, they digest bacteria and other food particles taken by the cell. In specialized cells of the human body, as in certain white blood cells, the digestion of bacteria and other disease-causing organisms is the body's first line of defense against infection.
Secondly, lysosomes are involved in the demolition of worn cellular organelles in a process known as autophagy. In plant cells, lysosomes can be implicated in the demolition of protoplasmas, which occurs in certain cell types as they mature. The products of lysosomal digestion are small molecules (amino acids, sugars, nucleotides, etc.) that from the place where the digestion took place spread into the cytoplasm where they are reused. Defects of the lysosomal function are thought to be responsible for many degenerative diseases, particularly those of the heart and brain.
THE ENDOPLASMATIC OR ERGASTOPLASMATIC RETICLE (RE)
Another membranous formation in the cell is that of the endoplasmic or ergastoplasmic reticulum. The membranes of the RE resume the three-dimensional structure of the cytoplasmic membrane; they are always double, so as to determine more or less large cavities (cisterns, tubules).
The ergastoplasmic reticulum can be covered with ribosomes (and then it is called wrinkled or granular), or smooth (or agranular). In the first case the lattice is mainly linked to protein synthesis.
Click on the names of the various organelles to read the in-depth analysis
Image taken from www.progettogea.com
Edited by: Lorenzo Boscariol
