This term indicates the continuous processes, both chemical and physical, to which the protoplasm is subject and which give rise to the continuous exchange of energy and substances between the external environment and the cell itself.
It stands out:
a) cellular anabolism, which includes all the processes by which the cell is enriched with vital substances and stores complex chemical molecules fundamental for its evolution and trophism;
b) cellular catabolism, which refers to all the destructive processes which the previously stored chemical molecules undergo; destruction that leads to the formation of energy with consequent elimination of waste.
All these processes can be gathered under a common denominator: cell turnover.
The intake of solid particles occurs by means of phagocytosis. This property was studied for the first time on the leukocytes of a mollusc by Haeckel, in 1862, and consists in the emission of pseudopodia (extensions, due to extroflexions of the cell membrane) or membranelle undulating, so that the material to be incorporated is circumscribed by these extensions and finally incorporated into the cytoplasm.
On the basis of their phagocitating properties, the cells have been divided into macrophages and microphages: the former are able to assimilate complete bacterial cells, while the microphages, on the other hand, are only corpuscular parts or residues of cells. Both types of phagocytic cells are abundantly represented in the human body. The functions to which these elements are delegated are: defense against germs and pathogenic microorganisms in general, elimination of atmospheric dust that reaches the pulmonary alveoli through respiration, elimination of debris from organs in the process of decomposition (as occurs for example in the metamorphosis of some animals) and finally the absorption of inflammatory processes. The main mechanism by which the cell feeds occurs through the absorption of liquid particles. In this respect, the cell membrane performs a fundamental function. In fact, it behaves like a semi-permeable membrane, like a filter, allowing the passage of certain substances and not others, albeit with considerable chemical affinity. It has also been noted that the membrane's willingness to absorb varies according to the functional state in which it is found: for example, if the cell, in a certain state, does not need lipids, although it can absorb them, it will not introduce them, in how much its needs are fulfilled for the moment.
Click on the names of the various organelles to read the in-depth study
Image taken from www.progettogea.com
See also: basal metabolic rate
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