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Basic aspects of cell









Introduction :

The cell is a minimum unit of an organization capable of acting autonomously. All living organisms arecomposed of cells, and it is generally accepted that no body is a living if it has at least one cell. Microscopic organisms such as bacteria and protozoa are single cells, while animals and plants are composed of many millions of cells organized into tissues and organs.

Although the virus and cell-free extracts perform many of the functions of living cells, no metabolism, growth andreproductive capacity (specific characteristics of living things) and therefore are not considered living organisms. Cell biology studies the cells according to their molecular constitution and the way they cooperate with each other to form complex organisms like humans. To understand how the healthy human body, how it develops and ages and what fails in case of illness, essential to know the cells thatconstitute it.

• Then try to further analyze the behavior, structure, and everything related to the cell
(Biology 2 nd half. Editorial Myrtle, pag1-2)

General characteristics of the cells:

There are cells of various shapes and sizes. Some of the smaller bacterial cells are cylindrical in shape less than one micron (1 micron equals one millionth of a meter). At the other extremeare the nerve cells, corpuscles of complex shape with many thin extensions that can reach several meters in length (neck of the giraffe are a spectacular example). Almost all plant cells have between 20 and 30 microns in length, shape and rigid cell wall. The animal tissue cells are usually compact, 10 to 20 microns in diameter and with a deformable surface membrane and almost always folded.Despite the many differences in appearance and function, all cells are wrapped in a membrane, called the plasma membrane, which encloses a water-rich substance called cytoplasm.

Inside the cells occur numerous chemical reactions that allow you to grow, produce energy and eliminate waste. All these reactions is called metabolism (a term that comes from a Greek word that means change.) All cellscontain the hereditary information encoded in deoxyribonucleic acid (DNA), this information directs the activity of the cell and ensures reproduction and the passing of traits to offspring.

These and numerous other similarities (including many molecules identical or almost identical) show that there is an evolutionary relationship between existing cells and first appeared on earth.Chemical composition:

In living organisms there is nothing that contradicts the laws of chemistry and physics. The chemistry of living things, the object of study of biochemistry, is dominated by carbon compounds and is characterized by reactions occurring in aqueous solution and a small temperature range. The chemistry of living organisms is very complex, more than any other knownchemical system. Is dominated by polymers coordinated large molecules made up of chain of chemical subunits, the unique properties of these compounds allow cells and organisms grow and reproduce. The main types of macromolecules are proteins, formed by linear chains of amino acids, nucleic acids, DNA and RNA, consisting of nucleotide bases, and polysaccharides, composed of sugar subunits.


The cell may exist as a separate entity because its membrane regulates the passage of materials to its exterior and interior. The cell membrane, or also called the plasma membrane only measures 7 to 9 nanometers thick.
All cell membranes, including those surrounding the various organelles, have this same structure, but differences in the composition of lipids and, in...