Cells cells are functional,physiological and morphological units of living
organisms. 2.0 Cell theory
The cell theory states that:
1.All organisms are composed of cells.
2.Cells are the basic unit of structure of organisms.
3.Cells are the basic unit of function of organisms.
4.Cells contain hereditary materials,which is passed from one generation to another.
5.All cells come from preexisting cells.
Structure of a cell Cell is the small unit of living organisms.While some organisms have millions of cells,some just have a single cell throughout life.Robert Hooke,an english scientist,first saw the cell structure in 1667.Cells can only be seen with the aid of a microscope.The cell of a plant under a light microscope has wall(i.ethe cell wall)made of cellulose.
The cell wall is permeable to water.Inside it is the cell membrane and the
cytoplasm.
Difference between plant and animal cell Animal cells are similar to plant cells.
Animal cell ------------------------- plant cell
1.cellulose cell wall is absent cell wall is present.
2.Vacuoles are absent when present small----alarge central vacuole is present.
3.chloroplast absent------------------------chloroplast is present.
4.it has no definite shape------------------it has definite shape.
5.cytoplasm is large.-----------------------cytoplasm is thin.
6.centriole is present.---------------------centriole is absent.
7.Glycogen granules present.----------------Starch granules present.
8.Lysosome present.-------------------------Lysosome absent.
Exercises
1.State the differences between a plant and an animal cell.
2.Draw and label
a.A plant cell and
b.An animal cell as viewed under both light and electron microscopes.
3.what are the functions of the various parts of a typical cell?.