Cell Theory Timeline

What is a cell? The basic unit of structure and function of life.

1665: Robert Hooke Builds compound microscopes and first to observe cork cells. Coined term “cell”

1683: Anton van Leeuwenhoek Builds simple, powerful microscopesBuilds simple, powerful microscopes Observes many single celled organisms, (like blood cells, animal sperm cells, & bacteria from his own teeth! He called them “animalcules” )Observes many single celled organisms, (like blood cells, animal sperm cells, & bacteria from his own teeth! He called them “animalcules” )

Discoveries that Led to Cell Theory Developed mainly by 3 German Scientist’s discoveries: a. Matthias Schleiden b. Theodor Schwann c. Rudolph Virchow

plants1838: Matthias Schleiden Concludes all plants are made of cells animals1839: Theodor Schwann Concludes all animals are made of cells.

1855: Virchow Concludes that all cells come from pre-existing cells

Cell Theory 1.All organisms are composed of one or more cells. 2.Cells are the basic units of structure and function in an organism. 3.Cells come only from the reproduction of existing cells.

Cell Diversity Shape: There are many cell shapes. The function of the cell influences the shape of the cell. For example, skin cells are flat, nerve cells have extensions.

Skin Cells Nerve cell

Size Different types of cells have different sizes. 0.1 μm – 100 μm The size of a cell is limited by the surface area-to volume ratio.

As the cell gets larger, the surface-area-to-volume ratio gets _smaller_.

Surface area-to-volume ratio Materials must enter through the surface. If a cell is too large, there is not enough surface area to allow materials to pass through quickly enough.

Types of Cells Prokaryotic vs. Eukaryotic

Prokaryotic Cells

1.Very simple cell 2.Generally smaller 3.NO membrane-bound organelles (compartments) 4.No true nucleus. –DNA is found in the nucleoid region and is NOT separated by a membrane. 5.Example is bacteria.

Eukaryotic Cell

1.More complex cells 2.Generally bigger 3.Contains membrane-bound organelles 4.Has a true nucleus –Region of where DNA is stored and is separated by a membrane. 5.Examples are animals & plants

1.Who is credited for first seeing cells? 2.According to the Cell Theory, where do all cells come from? 3.Which cells are simpler: Prokaryotic or Eukaryotic? 4.Which cells contain membrane- bound organelles? 5.Which type of cells do you have? Pop Quiz!