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.

Late1600’s: Anton van Leeuwenhoek Builds simple, powerful microscopes Observes many single celled organisms, (like blood cells, animal sperm cells, & bacteria from his own teeth! He called them “animalcules” )

1824: Henry Dutrochet All living things are made of cells 1831: Robert Brown Cells have a nucleus

1838: Matthias Schleiden Concludes all plants are made of cells 1839: Theodor Schwann Concludes all animals are made of cells.

Purkinje (1838): Jelly-like substance in cells called protoplasm Shultze (1861): protoplasm is the basis for life Dujardin (1860s): organisms can be unicellular

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

Cell Theory All organisms are composed of one or more cells. Cells are the basic units of structure and function in an organism. 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.

Surface area-to-volume Ratio larger As the cell gets ______, the surface-area-to-volume ratio gets _________. If the cell grows beyond a certain limit, not enough material will be able to cross the membrane fast enough to provide for the increased volume. smaller

Surface area-to-volume ratio Length of side Surface Area Volume Surface Area/ Volume 1 2 4 6 1 6 8 3 24 96 64 3/2 = 1.5

Surface area-to-volume ratio Materials must enter through the surface. The bigger the cell, the smaller the surface area-to-volume ratio. 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

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

Eukaryotic Cell

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

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

Viewing Cells Label, name, and state the functions of the parts of a compound microscope

Light Microscope Simple microscope: magnifying glass Uses light to produce enlarged image Light rays bend when passing through lens Simple microscope: magnifying glass Compound microscope: 2 lenses Multiply the magnification of each lens to get the total magnification.

Onion Cells

Stage clips: hold slide in place Diaphragm: adjusts amount of light Course adjustment: moves stage up and down to focus Fine adjustment: focuses on a smaller scale Eyepiece contains the ocular lens Nosepiece: holds objective lenses High power, medium power, low power