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

Cell Theory Cell Theory TimelineTimeline

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 Builds simple, powerful

microscopes microscopes

• Observes many single celled Observes many single celled organisms, (like blood cells, organisms, (like blood cells, animal sperm cells, & bacteria animal sperm cells, & bacteria from his own teeth! He called from his own teeth! He called them “animalcules” )them “animalcules” )

1824: Henry Dutrochet

• All living things are made of cells

1831: Robert Brown

• Cells have a nucleus

• 1838: Matthias Schleiden Concludes all plantsplants are made of cells

• 1839: Theodor Schwann Concludes all animalsanimals 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 TheoryCell Theory1.1. All organisms are composed of All organisms are composed of

one or more cells.one or more cells.

2.2. Cells are the basic units of Cells are the basic units of structure and function in an structure and function in an organism.organism.

3.3. Cells come only from the Cells come only from the reproduction of existing cells.reproduction of existing cells.

Cell DiversityCell 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• 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.

larger

smaller

Surface area-to-volume ratioSurface area-to-volume ratio

Length of side

Surface Area

Volume Surface Area/ Volume

1

2

4

6

24

96

1

8

64

6

3

3/2 = 1.5

Surface area-to-volume ratioSurface 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

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!

Viewing Cells

Label, name, and state the functions of the parts

of a compound microscope

Light Microscope

• 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