Commensal and Commensalism

Introduction Among the most known variants of symbiosis, commensalism plays a cardinal role: we are talking about a relationship established between two living organisms - known as commensals - in which a protagonist of the relationship takes advantage of it, while the other does not benefit from any benefit, nor is it damaged in any way

The karyotype

If a cell in mitosis is subjected to the action of substances such as colchicine, called mitotic, or antimitotic, or still statmocinetic, the mechanism of migration of centromeres in the melt is blocked and the chromosomes remain at the metaphase stage. With appropriate techniques it is possible to fix, photograph and enlarge the chromosomes, arranging them in a series ordered according to well-defined classification criteria (relative position of the centromere and size)

The eukaryotic cell

The eukaryotic type cell can be schematically divided into three main parts: the nucleus, the cytoplasm and a complex of membranes; in the cytoplasm there are also several other organelles. Dimensions and Cell Forms Most cells that make up the plant, or animal. it has diameters between 10 and 30 micrometers

The cytoplasm

The cytoplasm is the substance, prevalently colloidal in structure, included between the plasma membrane and the nuclear membrane. Molecules of smaller metabolites are dissolved in the cytoplasm: macromolecules. These can remain in the solution or gel state, thus causing changes in the cytoplasmic fluidity

Cell division

The continuity of living organisms is a general law that manifests itself differently in prokaryotic and eukaryotic, unicellular and multicellular organisms. The dividing cells go through a regular series of events that represent the cell cycle. The completion of the cycle requires variable periods of time, depending on the type of cell and external factors, such as the temperature or nutrients available

Cellular differentiation

EXAMPLES OF CELL DIFFERENTIATION The unity of a cell of a single-celled organism will take forms and structures, the most diverse, depending on the environment, the type of metabolism, etc. The increasing complexity of multicellular organisms and the individual cells that compose them come to assume increasingly specialized structures and functions, differentiating themselves in a varied (and more or less extreme) way from the cell type

Nitrogen bases

Generality The nitrogenous bases are aromatic heterocyclic organic compounds, containing nitrogen atoms, which take part in the formation of nucleotides. Fruit of the union of a nitrogenous base, a pentose (ie a sugar with 5 carbon atoms) and a phosphate group, nucleotides are the molecular units that make up the nucleic acids DNA and RNA

Plant Cell

The plant cell has some peculiarities that allow it to be distinguished from the animal; these include highly specific structures, such as the cell wall, vacuoles and plastids. Cell wall The cell wall constitutes the outer covering of the cell and represents a sort of rigid envelope formed essentially of cellulose; its particular robustness protects and supports the plant cell, but the reduced permeability hinders the exchanges with the other cells

Nucleic acids

Generality Nucleic acids are the great biological molecules DNA and RNA, whose presence and proper functioning, inside living cells, are fundamental for the survival of the latter. A generic nucleic acid derives from the union, in linear chains, of a high number of nucleotides. Figure: DNA molecule. Nucleotides are small molecules, in which three elements are involved: a phosphate group, a nitrogenous base and a sugar with 5 carbon atoms

Golgi apparatus and centrioles

THE GOLGI APPARATUS It is a complex of smooth membranes collected to form flattened sacks (cisterns or saccula) leaning against each other and often arranged concentrically, enclosing portions of cytoplasm rich in vacuoles. The edges of the cisterns, especially in the vegetables, are jagged; often, parts of them detach to form vesicles, which are small cavities enclosed in a membrane

The genetic code

For there to be a correspondence between the information of the polynucleotide and that of the polypeptide, there is a code: the genetic code. The general characteristics of the genetic code can be listed as follows: The genetic code is composed of triplets, and is devoid of internal punctuation (Crick & Brenner, )


Importance of Meiosis Within a multicellular organism it is necessary that all cells (not to recognize each other as foreign) have the same hereditary heritage. This is achieved by mitosis, dividing the chromosomes between the daughter cells, in which the equality of genetic information is ensured by the DNA reduplication mechanism, in a cellular continuity that goes from the zygote to the last cells of the body, in what it is called the somatic line of cellular generations

Lysosomes and endoplasmic reticulum

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 cell

- introduction - The cell, together with the nucleus, is the fundamental unit of life and living systems grow by cellular multiplication; it was the basis of every living organism, both animal and vegetable. The organism, based on the number of cells of which it is composed, can be monocellular (bacterium, protozoa, amoebae, etc

Movement, adaptability and cellular reproduction

Cell movement The ability of cells to move in a liquid or aeriform environment occurs through direct or indirect movement. The indirect movement is entirely passive, by means of the wind (it is the case of pollen), by means of water, or with the circulatory stream. A special type of indirect motion is the Brownian movement, which is performed with the collision of cells with colloidal molecules contained in a medium; this type of movement is very irregular (zigzag)

Mendelism, Mendel's laws

Mendel, Gregor - Bohemian naturalist (Heinzendorf, Silesia, 1822-Brno, Moravia, 1884). Having become an Augustinian friar, he entered the Brno convent in 1843; later he completed his scientific studies at the University of Vienna. From 1854 he taught physics and natural sciences in Brno. Between 1857 and 1868 he devoted himself in the convent garden to long practical experiments on pea hybridization

Cell membranes and plasma membrane

The type structure of the cell membrane consists of a phospholipid double layer between two protein layers located at the level of the separation surfaces between the internal and external phases of the cell. The lipid layer is bimolecular, with the polar groups facing the protein layer, while the apolar groups are facing with an isolation function

Cellular metabolism

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, in which all the processes by which the cell is enriched with substances vital to it and stores complex chemical molecules fundamental for its evolution and for its trophism are included; b) cellular catabolism, which means all the destructive processes that the previously stored chemical molecules face; destruction that leads


They have a predominantly tubular or ovoid shape. They are delimited by an external membrane similar to the cellular one; inside, separated by a space of about 60-80 A, there is a second membrane introflected in ridges, circumscribing a space occupied by the mitochondrial matrix. The inner membrane has a type of particles called elementary particles, on which the respiration enzymes are arranged in order (oxidative phosphorylation takes place in the mitochondria)


Mitosis is conventionally divided into four periods, called prophase, metaphase, anaphase and telophase respectively. They are followed by the division into two daughter cells, called cytodieresis. Prophase In the nucleus, colorable filaments are seen to gradually emerge, still elongated and wrapped in a ball


Generality DNA , or deoxyribonucleic acid , is the genetic heritage of many living organisms, including humans. Contained in the nucleus of cells and comparable to a long chain, DNA belongs to the category of nucleic acids, that is large biological molecules (macromolecules) formed by smaller molecular units that take the name of nucleotides


Without genetic variability, all living things should (by heredity) be equal to the first. To have unequal beings, the only explanations would be those related to single creations. But we know that the structure of DNA, which is the basis for the transmission of hereditary characters, has a relative and not absolute stability

Mitochondrial DNA

Generality Mitochondrial DNA , or mtDNA , is the deoxyribonucleic acid that resides inside the mitochondria, ie the organelles of eukaryotic cells responsible for the very important cellular process of oxidative phosphorylation. Mitochondrial DNA has some similarities with nuclear DNA, such as the double strand of nucleotides, the composition in terms of nitrogenous bases, the presence of genes, etc

Plastids or chloroplasts

They are organelles typical of vegetables, also surrounded, like mitochondria, by a double lipoproteic membrane. Inside there is a matrix containing round lamellas placed one above the other to form stacks called grains. Thin and little thick lamellae called stromal lamellae originate from the lamellae of the grains

Cell reproduction

The cyclic continuity of living beings finds in the phenomena of reproduction the connecting links between successive generations. Reproduction is carried out at different levels of the evolutionary scale, in the different branches of the vegetable and animal kingdoms, in the different living species, with such a variety of mechanisms that alone justifies an entire treatise


Neomendelism is the study of the phenomena that modify the transmission and manifestation of hereditary characters with respect to the schematic clarity of Mendel's laws. The characters chosen by Mendel for his experiments were diallelic, segregated independently and presented the phenomenon of dominance

The determination of sex

We have seen that in sexual reproduction we have male and female gametes. These are produced by organisms that are male or female respectively. But how is sex determined? In general the determination of sex is genotypic, that is, it depends on the chromosome set. Equally in general, the phenotypic gender corresponds to genotypic sex


Ribosomes are small particles, composed of RNA and proteins. Present in all the cells where protein synthesis takes place, they are composed of two subunits, one of which is slightly larger than the other, for which the presence of magnesium is necessary for adhesion. They have an analogous structure in prokaryotes and eukaryotes, but differing in mass, which is smaller in the former


Generality Protozoa are single-celled eukaryotic microorganisms, very common in nature. In fact, the more than 50, 000 different species of existing protozoa populate the most diverse habitats on the planet: from the ground to the deepest seas. Microbiologists considered it appropriate to distinguish protozoa based on the displacement mechanism

The nucleus

The nucleus contains, immersed in the so-called nuclear juice, or "carioplasma", DNA (chromatin, chromosomes), RNA (especially in the nucleolus), different proteins and metabolites. The spiraling of DNA in the chromosomes is not simple, but can be imagined as a spiral of spirals. In the intercinetic nucleus the higher spiralization is not sufficient to allow the individual chromosomes to be identified under the microscope


Generality Nucleotides are the organic molecules that make up the nucleic acids DNA and RNA. Nucleic acids are biological macromolecules of fundamental importance for the survival of a living organism, and nucleotides are the building blocks that constitute them. All nucleotides have a general structure that includes three molecular elements: a phosphate group, a pentose (ie a sugar with 5 carbon atoms) and a nitrogenous base

Nucleic acids and DNA

Nucleic acids are chemical compounds of great biological importance; all living organisms contain nucleic acids in the form of DNA and RNA (respectively deoxyribonucleic acid and ribonucleic acid). Nucleic acids are very important molecules because they exert primary control over vital vital processes in all organisms


Generality RNA , or ribonucleic acid , is the nucleic acid involved in the processes of coding, decoding, regulation and expression of genes. Genes are more or less long segments of DNA, which contain the fundamental information for protein synthesis. Figure: Nitrogen bases in an RNA molecule. From wikipedia

From the Spontaneous Generation Theory to the Bacteria Discovery

Although today it may seem obvious it is obvious, for millennia man has ignored the fact that microscopic organisms caused certain diseases. Until 1600, the so-called theory of spontaneous generation was considered valid, according to which some organisms can spontaneously be generated from non-living matter

Number of Cells in the Human Body

3.72 × 1013, that is: 37, 200, 000, 000, 000 or 37, 200 billion. This is the number of cells that roughly make up the human body , according to a recent study1 published in the journal Annals of Human Biology. It means that in a single human body there are about 5, 000 times more cells than the number of world population.

Calculate blood type

See also: blood type and blood group diet The tables proposed in this article allow you to quickly calculate the compatibility of a subject's blood group with that of their parents. The first scheme allows us to establish the possible blood group of a child knowing the blood group of the mother and the alleged father

From the extracellular matrix to posture. Is the connective system our real Deus ex machina?

By Dr. Giovanni Chetta General index Premise Extra-cellular matrix (MEC) Introduction Structural proteins Specialized proteins Glucosaminoglycans (GAGs) and proteoglycans (PGs) The extracellular network Remodeling of the MEC MEC and pathologies Connective tissue Introduction Connective band Fascial mechanoceptors myofibroblasts Deep-band biomechanics Viscoelasticity of the fascia Posture and tensegrity Dynamic balance Function and structure Tensegrity Praise to the propeller The engine of man's specific motion Static

Aerobic and Anaerobic bacteria

Generality The classification of bacterial species in aerobic and anaerobic bacteria is performed according to the energy source used to feed the biosynthetic processes of their metabolism. More precisely, the classification in aerobic and anaerobic bacteria refers to the effect that oxygen (O 2 ) has on the growth of the microorganisms in question