cells and microbes

Cells and microbes
Pathogenous micro-organisms
Pathogenous micro-organisms are those which can cause diseases or infection if they get inside our body.
There are three kinds of pathogenous micro-organism: viruses, bacteria and protozoa.
They can get into our body in different ways.
Digestive, ingested with food.
Respiratory, through inhalation, via the nose when breathing.
Sexual, throughvaginal mucosae and the penis during sexual relationships.
Cutaneous, through the skin via a wound.
In the interior of the body the micro-organisms find a favourable medium and they reproduce in large quantities causing an invasion. The most common symptoms are a fever and feeling ill.
Our body reacts against them in many different ways by means of the immunes system. The affected area becomesswollen and red; this is known as an inflammation, because a large number of leucocytes and plasma are sent to fight against the invasion of the micro-organisms. At the end of the fight, there is often pus, which is a substance which is formed by the remains of the micro-organisms and the leucocytes.
If the infection is general, it can be lethal. However, medicine has created special substancesto help to fight infection. These are antibiotics and vaccines.
Viruses
Viruses are not organisms, they are proteinic molecules which are joined together forming an envelope or capsule which contains a DNA or RNA molecule. They are so small that they can only be seen under an electron microscope. They have no activity outside of an organism, but, once in the interior of cells, they are able toreproduce and cause diseases.
There are different kinds of viruses. They may very in shape: some are icosahedral, such as polio mellitus; and others are heliocoidal, like the tobacco mosaic virus (a disease of the tobacco plant). Bacteriophages only infect bacteria. Some viruses, such as smallpox, flu or AIDS, have a protein envelope that is very similar to the membrane of human cells. This makethe cells believe the virus is part of the organism and take it in, resulting in infection.
When a virus enters a cell, its nucleic acid begins to duplicate and each one of the copies uses ribosomes and the amino acids of the infected cell to make its own proteins. They then join together making new viruses which leave the cell and infect healthy cells.
Protozoa
Protozoa are eucaryotic,unicellular organisms, generally having heterotrophous respiration, which live in all kinds of water mediums. Their structure is that of a typical eucaryotic cell and the presence of cilia, flagella and pseudopods are used to classify them into groups.
Flagellated, these have flagella and include Trypanosoma, which causes sleeping sickness, and Giardia, an intestinal parasite.
Ciliated, the surface iscovered with cilia. An example of this is the paramecium, which is shaped like a slipper (it is not a pathogen).
Rhizopods: these use pseudopods to move or the capture food particles, such as Amoebae.
Sporozoa: these reproduce through spores, such as Plasmodium, which causes malaria.
Bacteria
Bacteria are unicellular living organisms which are very small but visible under an optical microscope.They are procaryotic cells which are able to live in all mediums, even very extreme ones.
According to their shape, these may be:
Cocci: if they are round. They can join together in two (diplococci), in rows (streptococci) and bunches (staphylococci).
Bacilli: if they are rod-shaped. They may join together in rows (streptobacilli).
Vibrio, in the shape of a comma.
Spirals, long and a littleheliocoidal.
There are autotrophic and heterotrophic bacteria. Some bacteria need oxygen to live (aerobic) and others live without oxygen (anaerobic).
Among pathogenic bacteria we can include Salmonella typhi, which causes typhus, Chlostridium tetani, which causes tetanus and the Koch bacillus, a micro-organism which causes tuberculosis.
Microorganismos patógenas
Microorganismos patógenas...