The Cell and Its Organelles PDF

THE CELL  One of the characteristics of life is the presence of cells. All living organisms have cells. It is known as the basic unit of life. Some organisms have a single cell which performs all the functions necessary for survival. While the higher forms of life have more than...

THE CELL  One of the characteristics of life is the presence of cells. All living organisms have cells. It is known as the basic unit of life. Some organisms have a single cell which performs all the functions necessary for survival. While the higher forms of life have more than one cell or are  As a matter of fact, every cell is a highly functional unit with several subunits with specific roles to play. The cells are composed of macromolecules: carbohydrates, lipids, nucleic acids and proteins. It is also composed of organelles.  In the case of multicellular organisms, the cells are highly modified for the roles they play. Cardiac cells are not similar with nerve cells, red blood cells or pancreatic cells. Their structure and size varies depending on the  The idea that every living organism is composed of cells was first proposed by Anton van Leeuwenhoek when he saw tiny living organisms from a drop of water from the pond.  Beginning in 1674, viewing a drop of pond water, he observed things moving which he called "animalcules." This was the first documented view of the living microworld, that there are living things in the world that our naked eyes cannot see, but with the invention of magnifying tools,  Animalcule is an old term for microscopic organisms that included bacteria, protozoans, and very small animals.  It was also later supported by Robert Hooke in 1665. He cut a slice of cork and saw thousands compartments in the microscope. It was Hooke who first called these compartments as cells.  He remarked that it looked strangely similar to cellula or small rooms which monks inhabited, thus deriving the name. However what Hooke actually saw was the dead cell walls of plant cells (cork) as it appeared under the microscope.  Mature cork cells are plant cells that form the protective water-resistant tissue in the outer covering of stems or trunks. The outer protective coat of a tree is called cork. It is one of the components of tree bark.  In 1838, a German botanist named Matthias Schleiden studied and found out that all plants are made up of cells. A similar discovery was proposed by Theodor Schwann.  In 1885, another idea about cells was proposed by Rudolf Virchow who concluded that cells come from preexisting cells. Thus, the cell theory was born. THE CELL THEORY PREMISE 1. All living things are composed of cells. 2. Cells are the basic unit of structure and function in living things. 3. New cells are produced from preexisting cells.