Cell HistoryChapter 7

http://www.guardian.co.uk/science/2008/jul/01/stem.cell

What Is A Cell?• What is a cell?

–Building block of living things–Smallest unit capable of life function

–too small to see with the naked eye–many times smaller than a grain of sand

http://library.thinkquest.org/C004535/eukaryote_examples.html

A What?

• What invention was responsible for the discovery of the cell?

Role of the Microscope

• After the invention of the microscope in mid 1600's

• Grew with the advancement microscope technology

http://library.thinkquest.org/C004535/studying_cells.html

Light Microscopes

• Allow us to

• view up to 2000 times

• see many cell structures of plants and animals

http://www.biology.arizona.edu/CELL_BIO/tutorials/cells/cells2.html

Transmission Electron Microscopes

• 1000 times stronger than the light microscope

• TEM

http://www.biology.arizona.edu/CELL_BIO/tutorials/cells/cells2.html

Scanning Electron Microscope

• Produces three‑dimensional images

• See the smallest cells with clear and defined detail

• SEM

http://www.biology.arizona.edu/CELL_BIO/tutorials/cells/cells2.html

Robert Hooke

• 1635-1703

• (1665) observed a slice of cork– saw little boxes– boxes looked like cells

• Same pattern in stems and roots of plants (carrots, ferns, trees) – actually dead plant cells– did not know that cells were the basic unit of life

Anton Van Leewenhoek

• 1632-1723

• Microscope maker

• Observed living cells

–Clear pond water–Named organisms “animalcules” (tiny animals)

–Now we know these as protists (most diverse)

Matthias Schleiden

• 1804-1881

• (1838) Botanist

• All plants were “composed of cells”

• Cells are not only in the stems and roots of plants, but all over the plant.

Theordor Schwann

• 1810-1882

• (1839) Zoologist

• “all animals (**SWAN**) were made up of cells”

Rudolf Virchow

• 1821-1902

• (1858) German physician

• Studying how diseases affect living things

• Observed that cells only come from other cells

Cell Theory

• Where can I find a cell?

• What is a cell?

• Where do cells come from?

Cell Theory

• 1. All living things are composed of one or more cells.

• 2. In organisms, cells are the basic units of structure and function.

• 3. Cells are produced only from existing cells.

Cell Differentiation

• All cells are not alike, but they do have similarities, which they all share. Even in the same organism all cells are not alike. They may be different in size, shape and internal organization.

Levels of Organization

Muscle cell

Smooth muscle tissue

Stomach

Digestive system

Cell Differentiation

• Cells

• Tissues

• Organs

• Organ System

• Organism

Organism “Size”

• Unicellular–Composed of one cell–Does not allow for specialization (1 cell=everything)

• Multicellular–Composed of more than one cell–Allows for specific cells to specialize–(Ex. Nerve cells- conduct messages by nerve impulses through body)

–Human body 100 trillion cells (1x1014)

Why Are Cells Small?• 1) Increased surface area allows for

exchange in and out of cell–Interaction with environment–Waste disposal, Food intake, Oxygen intake)

• EFFICIENCY IS DEPENDENT UPON RATIO OF SURFACE AREA TO VOLUME!!!

• THE LARGER THE CELL THE LARGER THE SURFACE AREA NEEDED TO MAINTAIN IT!!!

• 2) If the cell is smaller then it allows materials to move faster to their destination–Shorter radius/diameter of cell–Shorter distance to location

Different Cell Types

Categories of Cells

Prokaryotes

• Simple (no specialized structures)• No specialized function• Single-celled• Oldest type (3.5 mya)• Alone for 2 billion years• Oldest fossils cyanobacteria• Circular DNA in cell• Ex. Bacteria)

Eukaryotes

• Complex (has specialized structures)

• Specialized function• Single-celled/Multi-celled• Newest type (1.5 mya)• Linear DNA in nucleus• Ex. All cells except bacteria