Discovery of the Cell and Cell Theory

Observations of Dead Cells

• Robert Hooke (1635-1703) – First to view cells

(dead cork cells)– Thought that the “little

boxes” looked like the rooms where monks lived (cells)

Observations of Living Cells

• Anton van Leeuwenhoek (1632-1723) – First to observe living

cells

Observations of Living Cells cont.

• Matthias Schleiden (1804-1881)– Concluded that all plants were

made of cells

Observations of Living Cells cont.

• Theodor Schwann (1810-1882)– Concluded that all animals were made of cells

Observations of Living Cells cont.

• Rudolf Virchow (1821-1902)– Determined that cells only come

from other cells

The Cell Theory (putting the observations together)

1. All living things 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.

What did Microscopes help scientists discover about all living

things?• Look back at your acrostic poem, your

handout from yesterday, and your handout from last Monday. Otherwise use your textbook:

• Describe how Cell Theory was developed by what scientists had discovered thanks to microscopes

All Things are made of Cells!

• As microscopes got more complex, even small cells and single celled organisms could be studied.

• With this came the discovery of prokaryotes vs eukaryotes.

• Pro-before

• Karyote-kernel or nut

• Eu-true or good

Eukaryotic Vs Prokaryotic

Prokaryotic Cell

Eukaryotic Cell

In your notes, write down what you see as the difference between the 2 cells.

• All cells fall into one of two categories: prokaryotic or eukaryotic

• Prokaryotic cells evolved earlier in history than eukaryotic cells

• Prokaryotic cells lack several of the features found in eukaryotic cells

• You are eukaryotic.– Your cells have a nucleus and

membrane-bound organelles.

Prokaryotes

Eukaryotes

Prokaryotic vs. Eukaryotic cont.

Prokaryotic Cell Eukaryotic Cell

Cell Membrane

May be unicellular

May be multicellular

Has membrane-bound organelles

Has a membrane-bound nucleus

Contains DNA or other genetic info

How are Prokaryotes and Eukaryotes Different?

• Look over your notes and describe the differences between a prokaryote and eukaryote.

• How does knowing the root of the word help you to describe this difference?

Intro to Cell Structure

• Quick Review:– Cells = basic unit of life– Unicellular: the organism is just one cell– Multicellular: the organism has lots of cells,

each carries out a specific job

• All cells have:– Cell membrane– Cytoplasm (with organelles)– DNA (genetic material)

Cell membrane

• Thin barrier separating the cytoplasm and contents of the cell from the external environment.

• In some cells the membrane is surrounded by a cell wall.– The cell wall is a thick, rigid structure

surrounding plant and bacteria cells.

Inside a Cell

• Cytoplasm – space inside the cell, between the membrane and

nucleus that contains a semi-liquid substance and houses the organelles.

• Nucleus – spherical organelle that contains the DNA of

eukaryotic cells.• Visible in most cells under a light microscope• All plant and animal cells are eukaryotic.

• Organelles = – specialized structures that carry out cell functions

• Most are not visible using only a light microscope

Finish your Microscope poster for tomorrow

• Come ready to take a test.

• Bring your Green Lab Manual, and read over Lab 6.

Onion Cells

Elodea Cells

Cheek Cells