Cell Theory 1. Anton van Leeuwenhoek, a Dutch biologist working in the 1600’s, is given credit for developing the 1st microscope. He observed tiny organisms in pond water & made drawings of them.

Cell Theory

Cell Theory 2. Robert Hooke, an English scientist, used a microscope (in 1665) to look at pieces of cork. He saw thousands of tiny chambers which he called cells. His discovery was significant because it opened up the study of cells.

Cell Theory 3. Robert Brown, a Scottish scientist, who in 1833 observed that cells seemed to have a dark structure near the center of the cell. We now call this structure the nucleus.

Cell Theory 4. Matthias Schleiden, a German botanist, stated in 1838 that all plants are made of cells. 5. Theodore Schwann, a German zoologist, in 1839, discovered that all animals are made of cells.

Cell Theory division of preexisting cells. 6. Rudolf Virchow, a German physician, stated in 1855, that all cells arise from the division of preexisting cells.

Cell Theory The observations and conclusions of these scientists are summarized into the Cell Theory. The cell theory states: 1. All living things are composed of cells. 2. Cells are the basic unit of structure and function in living things. 3. All cells come from preexisting cells.

Cell Structure There is enormous variety in the size and shape of cells. Cell diameter ranges from the smallest cells at 0.2 micrometers in diameter, to the larger cells at 1000 micrometers in diameter. Most cells, however, range between 5 and 50 micrometers in diameter.

Cell Structure Physical limits on the flow of information through the cell and on the flow of materials into and out of the cell, limit cell size.

Cell Structure Despite differences in size and shape, cells of animals, plants, and related organisms have three basic structures: (1) cell membrane (2) nucleus (3) cytoplasm

Cell Structure

Cell Structure: (1) Cell Membrane Cells are separated from their surroundings by a cell membrane also called a plasma membrane. The cell membrane: (a) Regulates what enters & leaves the cell. (b) Aids in the protection & support of the cell. (c) Communicates with other cells.

Cell Structure: (1) Cell Membrane The cell membrane is composed of a double layer of lipid molecules known as a bilayer. The major lipids in biological membranes are phospholipids.

Cell Structure: (1) Cell Membrane The bilayer consists of two regions: A head region with a circular phosphate group (The head region is polar & therefore hydrophilic A tail region made up of long fatty acid chains. (The tail portion is nonpolar & therefore hydrophobic.)

Cell Structure: (1) Cell Membrane