Cells The cell is the basic structure and unit of all known living organisms.

Definition It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. Organisms can be classified as unicellular (consisting of a single cell; including most bacteria) or multicellular (including plants and animals). Humans contain about 10 trillion (10^13) cells. Most plant and animal cells are between 1 and 100 µm and therefore are visible only with the use of a microscope. Escherichia bacterias

The discovery The cell was discovered by Robert Hooke in All organisms are composed of one or more cells which come from preexisting cells. The vital functions of an organism take place within cells, and all cells contain the hereditary information necessary for regulating their functions and for transmitting information to the next generation of cells. The word cell comes from the Latin cellula, meaning "a small room". The descriptive term for the smallest living biological structure was coined by Robert Hooke in a book he published in 1665 when he compared the cork cells he saw through his microscope to the small rooms monks lived in.

Prokaryotes & Eukaryotes There are two basic types of cell: prokaryotic, which is smaller and does not show the nucleus and eukaryotic, which contains the nucleus delimited by a membrane. The structure of plant and animal cells is very similar because they are both eukaryotic cells; however animal cells seem simpler to study than plant cells, because they are composed of fewer parts.

Animal and Plant cells Eukaryotic cells are divided into two main groups: Animal and Plant cells. Both of them have a cell membrane, a cytoplasm and a nucleus. But these two groups differ a lot from each other, mainly because Plant cells have a cell wall around the cell membrane and only Plant cells can do the photosinthesis. Also Plant cells have a vacuole and chloroplasts

DNA Inside the nucleus we can find the most important cell molecule: the DNA. It is a giant archive containing all the genetic information needed by the organism. It contains proteic sequences, information about somatic features, and other genes whose function is still unknown.

History and structure DNA means DeoxyriboNucleic Acid. Its structure was formulated by Watson and Crick combining all the previous knowledge discovered since then. The DNA has a double-helix structure and can be folded several times to fit in the tiny cell's nucleus. Watson and Crick with the original DNA model

Mitosis Mitosis is a type of cell division, and is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly equal shares of these cellular components. Mitosis and cytokinesis together define the mitotic phase of the cell cycle which is the division of the mother cell into two daughter cells, genetically identical to each other and to their parent cell. This accounts for approximately 10% of the cell cycle.

Stem Cells

Features Stem cells are biological cells found in all multicellular organisms, that can divide (through mitosis) and differentiate into diverse specialized cell types and can self-renew to produce more stem cells. In mammals, there are two broad types of stem cells: embryonic stem cells, which are isolated from the inner cell mass of blastocysts, and adult stem cells, which are found in various tissues. In adult organisms, stem cells and progenitor cells act as a repair system for the body, replacing adult tissues. In a developing embryo, stem cells can differentiate into all the specialized cells (these are called pluripotent cells), but also maintain the normal turnover of regenerative organs, such as blood, skin, or intestinal tissues.

Potency Potency specifies the differentiation potential (the potential to differentiate into different cell types) of the stem cell. Totipotent (a.k.a. omnipotent) stem cells can differentiate into embryonic and extraembryonic cell types. Such cells can construct a complete, viable organism. These cells are produced from the fusion of an egg and sperm cell. Cells produced by the first few divisions of the fertilized egg are also totipotent. Pluripotent stem cells are the descendants of totipotent cells and can differentiate into nearly all cells, i.e. cells derived from any of the three germ layers. Multipotent stem cells can differentiate into a number of cells, but only those of a closely related family of cells. Oligopotent stem cells can differentiate into only a few cells, such as lymphoid or myeloid stem cells. Unipotent cells can produce only one cell type, their own, but have the property of self-renewal, which distinguishes them from non-stem cells (e.g., muscle stem cells).

Harvesting There are three basic types of stem cells. Fetal stem cells are found in human beings during the fetal stage of development and can be harvested from aborted fetuses or from the umbilical cord of a newly delivered baby. Embryonic stem cells are found in embryos and are generally harvested from frozen embryos that are designated to be incinerated as medical waste. Adult stem cells, on the other hand, are found in many different tissues within the human body and can be harvested, to a limited extent, without harming the individual or causing excessive pain.

Treatments Medical researchers believe that stem cell therapy has the potential to dramatically change the treatment of human disease. A number of adult stem cell therapies already exist, particularly bone marrow transplants that are used to treat leukemia. In the future, medical researchers anticipate being able to use technologies derived from stem cell research to treat a wider variety of diseases including cancer, Parkinson's disease, spinal cord injuries, Amyotrophic lateral sclerosis, multiple sclerosis, and muscle damage, amongst a number of other impairments and conditions. However, there still exists a great deal of social and scientific uncertainty surrounding stem cell research, which could possibly be overcome through public debate and future research, and further education of the public. Stem cells are widely studied, for their potential therapeutic use and for their inherent interest.

Controversy One concern of treatment is the risk that transplanted stem cells could form tumors and become cancerous if cell division continues uncontrollably. The side effects for bone marrow and stem cell transplants are really the same as for chemotherapy. You are having the same drugs in higher doses. So the side effects can be very severe. All these side effects are at their worst when you have just had your transplant and for a couple of weeks afterwards. When your blood counts start to rise you will start to feel better. In the longer term, these treatments may cause infertility, although some people who have had a transplant do go on to have children.

The End Niccolò Izzo / Luca Panzoli Sources: wikipedia.org and google.comwikipedia.orggoogle.com