The Cell Theory All living things are made up of cells. Some organisms are composed of only one cell. (unicellular) Other organisms are made up of many cells. (multi-cellular)

Advantages? 1. What are the advantages of a one-celled organism? 2. What are the advantages of an organism that is made up of many cells?

1600’s Anton Van Leeuwenhoek was the first person to see tiny living organisms in a drop of water by using a primitive microscope.

1665 British physicist Robert Hooke used one of the first light microscopes (like we use today), to look at thin slices of plant tissues (cork). A piece of cork under the microscope looks like thousands of tiny chambers that Hooke called cells because they reminded him of a monastery’s tiny rooms, which were also known as cells. This is how we got the term cells.

Hooke continued… Hooke’s discovery of cells led other scientists to search for cells. Before long, it became apparent that cells were the basic units of all forms of life.

1838 German botanist Matthias Schleiden concluded that all PLANTS are made up of cells

1839 German scientist, Theodor Schwann, concluded that all ANIMALS are also made up of cells.

1855 Rudolf Virchow, a German Physician, studied cell reproduction and concluded that “where a cell exists, there must have been a pre-existing cell…”

The Cell Theory All of these scientists contributed to the cell theory. The cell theory states the following: 1. All living things are composed of cells.

The Cell Theory continued… 2. Cells are the basic units of structure and function in living things. 3. New cells are produced from existing cells.

Basic Cell Structures Cells come in many shapes and sizes but almost all cells have some basic structures. The cell membrane is a thin, flexible barrier around the cell. In 1931, Janet Plowe (WOW! A WOMAN scientist finally!) demonstrated that the cell membrane is a physical structure and not an interface between two liquids. Plant cells have a Cell Wall that is stronger than the cell membrane and protects the cell.

Basic Structures continued… Some cells also have a nucleus, which is a large structure that contains the cell’s genetic material and controls the cell’s activities. (office of the cell) The material inside the cell membrane—but does not include the nucleus—is called the cytoplasm.

Different Categories of Cells Biologists divide cells into 2 categories: Prokaryotes and Eukaryotes. The cells of Prokaryotes DO NOT have a nucleus. The cells of Eukaryotes DO have a nucleus.

Prokaryotes The way to remember about a Prokaryotic cell is that “Pro has NO nucleus!” They are smaller and simpler than Eukaryotes. ALL BACTERIA ARE PROKARYOTES!

Eukaryotes The way to remember about a Eukaryotic cell is that “Eu has a TRUE nucleus”. These also have specialized structures called organelles.

Organelles In 1970, Lynn Margulis, (WOW! Another WOMAN scientist who is still alive and lives in Amherst, Massachusetts) proposed the theory that certain organelles were once free-living cells themselves. You will have to know the different organelles, their structures and functions

See the Differences? Prokaryotic Cell Eukaryotic Cell Cell membrane Cytoplasm Prokaryotic Cell Cell membrane Cytoplasm Nucleus Organelles Eukaryotic Cell