Cells are generally microscopic and the cell size varies greatly. * Prokaryotic cells measure 0. 1 micrometer to 5 micrometer. Eukaryotic cell can measure from 1 micrometer to several centimeters. Smallest cell is that of mycoplasma gallisepticum ,which are only 0. 3 micrometer wjile the bacteria could to be 3 to 5 micrometer. * Largest cell is that of Ostrich egg, measures 17*15 cm wide. * Among multicellular organisms , human red cells are about 7. 0 micrometer in diameter. * Nerve cells are some of the longest cells . Cell shape: * Shapes of cells vary greatly. * In plants, generally cells have a definite shape due to the presence of a rigid cell wall. * Most of the plant cells are spherical or polyhedral (many sided as in parenchyma .
It may be cylindrical as in green algae . Needle shaped as in fibres etc. * Animals exhibit a greater diversity in cell shape. They are column -like as in epithelial cells, fibre -like elongated as in muscle cells, biconcave shaped like RBC etc. * The shape of the cell may vary with the function they perform. Unicellular and multicellular organisms: * All organisms whose body is made of single cell are called Unicellular. * Eg: Ameoba, Euglena. * All organisms whose body is made of several cell are called Multicellular. * Eg :Plants, Animals.
Eukaryotic and Prokaryotic cells: Eukaryotic cells: are cells with True nucleus where the genetic material is bound by a nuclear membrane . All the organisms with such a nucleus is called prokaryotes. Eg: higher plants and animals including humans. Prokaryotic cells: are cells with a primitive nucleus, where the genetic material is not bound by a such a nucleus is also called nucleiod or incipient nucleus. Eg: Bacteria, Blue green algae and PPLO(Pleuro Pneumonia Like Organisms) as mycoplasma. Ultra structure of a Prokaryotic cell(Bacterial cell):
The Essay on Take Home Assignment – Biology Cell Analysis
Size, Structure and Microscopy Introduction What is life? What are the key factors that biologists have defined that apply to every single organism on the planet? In the 17th century, due to the amazing advancement of the microscope, biologists created a theory to differentiate the living from the non-living called the cell theory. One concept from the theory is that all living organisms are ...
