The study of cells and micro organisms has changed over time with the change in technology.

These were studied in the beginning with hand lenses, single lens microscope, light microscope

Today we have electron microscopes.

Two types of electron microscopes are used today: SEM – Scanning electron microscope and TEM –Transmission electron microscope.

He discovered the microscope with one lens

Discovered

- bacteria

- blood cells

- spermatozoa

- protozoa

Uses the concept cell for the first time.

He used it when he looked at the microscopic structure of cork cells.

Describes the nucleus of a cell

Developed the cell theory:

- Plants and animals are made of groups

of cells.

- The cell is the basic unit of living

organisms

Expanded the cell theory:

He said that new cells formed by the division of existing cells

Expanded the cell theory more:

He said that all cells can be traced to their origin

All living organisms are made out of cells

New cells are formed by the division of existing cells

The cell houses genes, which are the blueprint for growth, functioning and development of cells

The cell is the functional unit of life because all chemical reactions of life take place inside the cell

A cell is the basic unit of structure and function in organisms.

Cells differ in size, shape and in function.

Two types of cellsProkaryotic or Eukaryotic cells.

Only organisms of the domains Bacteria

and Archaea consist of prokaryotic cells –

cells without a membrane bound nucleus.

Protists, fungi, animals and plants all

consist of eukaryotic cells – cell with a

membrane bound nucleus.

CELL WALL(ONLY IN PLANT CELLS) Varies in thickness Consist of pectin (elasticity), cellulose fibrils held

together with non-cellulose substances (hardens the cell when mature) and lignin (adds strength to cell especially in woody plants)

Cell wall is permeable and protects the inside of the cell.

Middle lamella (layer of adhesive substances) – holds the cells together

Plasmodesmata (pores) that connects the cytoplasm of the connecting cells – selectively permeable

CELL MEMBRANE/PLASMA- (ANIMAL- AND PLANT CELLS)

Consist of 2 phospholipid layers and proteins in between.

The phospholipid layers are part hydrophillic and part hydrophobic

NUCLEUS +/- 5µm, largest organelle in cell.

Enclosed by a nucleomembrane with nuclear pores. Function: Protection and add to selective permeability.

Filled with nucleoplasma, a nucleolus and chromatin. Function of chromatin: carries genetic material in the form of chromosomes.

Function of nucleolus: Produce r-RNA

STRUCTURE OF NUCLEUS