01. What is Cell Biology?
Branch of biology that deals with various aspects of structure, chemistry, development, genetics and functioning of cells are called cell biology.
2. Basic unit :
The cell is the basic unit of life as no organism can have life without being cellular because the cell is a unit of both structure and function.
Organisms types ( on the basis of cell types)
Unicellular or acellular (organisms made of a single cell)
Eg: chlamydomonas, acetabularia, bacteria,yeast,amoeba
Multicellular (organisms made of many cells)
E.G., newly born infant (2 x 1012 cells)
3. Discovery of the cell:
1: Zacharias Janssen (1590): built the first microscope
2: Galileo (1610): Modified Microscope
3: Robert Hooke (1635-1703): a developed new microscope with which he studied the internal structure of a number of plants. His work was famous for the study of cork cells.
Robert Hooke > took a piece of cork of Spanish oak > prepared thin slice by means of sharp pen knife > deep planoconcave lens used for throwing light > latter observed > cork had honeycomb structure with number of box-like compartments, each having a pore and separated from others by diaphragms > named as cellular (now known as cells).
Hooke microscope and structure of cork cells
4: Leeuwenhoek (1673): first to describe and sketch a live cell. He observed protozoa, spermatozoa, red blood cells etc.
5: Malpighi (1675) & grew (1682): gave an account of the internal structure of plants.
6: Mirbel (1802): said "Plants are formed by membranous cellular tissue"
7: Dutrochet (1824): stated " all organic tissues are really globular cells of an extreme smallness which are united by cohesion"
8: Robert Brown (1831) discovered the presence of nucleus in the cells of the orchid root.
9: Dujardin (1835): living semifluid substance of cells > named sarcode
10: Schleiden (1838): found all plant cells to have a similar structure- cell wall, a clear jelly-like substance and a nucleus.
11: Schwann(1838): discovered that animal cells lacked the cell wall.
12: Purkinje and Mohl (1838): renamed sarcode or jelly-like the substance of the cells as protoplasm
