1. Cell Theory
Prokaryotes &
Eukaryotes

2. Introduction Living organisms are made up of CELLS
Living organisms can be made up of one cell or many hundreds of millions of cells
Unicellular – life forms consist of only one cell
Multicellular – life forms are made of many cells
November 9, 2018

3. Some Unicellular Life Forms:
E. Coli – a mostly friendly bacteria that lives in our gut
Paramecium – a pond water creature that eats bacteria
Amoeba – a pond water predator that may eat paramecium
Size: 2 micrometers (millionth of a metre)
Size: micrometers
Size: micrometers
November 9, 2018

4. Some Multicellular Life Forms:
Grass – a common plant Cow – a common creature that eats grass Human – a life form that may eat a cow
November 9, 2018

5. Humans & Cells Made of trillions of cells Of those trillions there are
only about 200 different varieties
For example: brain cell, muscle cell & red blood cell
All humans began as one cell that grew & divided into trillions!
November 9, 2018

6. We Are Not Alone! Microorganisms live all over and inside our body!
Skin (surface & deep layers)
Saliva
Intestine
Stomach
Eyes, nose & ears
The number of human cells (trillions) are OUTNUMBERED by the number of bacteria, fungi & other microorganisms by at least a factor of 10 : 1 !!
(For every 1 human cell, we have 10 microorganisms living with us)
November 9, 2018

7. Discovery of Cells – Robert Hooke
1665 – English scientist, Robert Hooke, discovered cells while looking through one of the first microscopes Looked at a thin slice of cork and described what he saw as “tiny boxes or honeycombs” Named the boxes “cells” as they reminded him of the cells in monasteries Thought cells only existed in plants
November 9, 2018

8. Anton van Leuwenhoek 1673 - Anton van Leuwenhoek used a
handmade microscope to observe
pond scum & discovered
single-celled organisms
He called them “animalcules”
He also observed blood cells from fish, birds, frogs, dogs, and humans
Therefore, it was known that cells are
found in animals as well as plants
November 9, 2018

9. Spontaneous Generation????
Next years - Very little research on cells because widely accepted view of life was maintained by the church, which frowned on modern science
Their theory was based on observations such as…
Dead logs were the source of mushrooms
Rotting meat was the source of flies
Mouldy hay was the source of mice
Spontaneous Generation – living organisms arose from non-living objects
November 9, 2018

10. How would you disprove Spontaneous Generation?
Many scientists were sceptical of Spontaneous Generation & set about to understand how organisms come into existence (through the scientific method!)
A jar of rotting meat
People used to believe that flies came from the rotting meat
How would you prove that flies were not a by-product of the rotting meat?
November 9, 2018

11. Development of Cell Theory – 1800’s
1833 – Robert Brown
Observed the nucleus in the epidermis of an orchid
November 9, 2018

12. Schleiden and Schwann
Matthias Schleiden, a German professor of botany, conclusively identified the first plant cells and concluded that all parts of a plant is made of cells
1839 – Theodor Schwann, a German physiologist, who was a close friend of Schleiden, stated that all animal tissues are composed of cells.
November 9, 2018

13. Rudolf Virchow
1855 – Rudolf Virchow, German physician, now known as the father of modern pathology
Discovered that all disease results as an injury to the cell
Proved that cells arise from other cells, not from non-living matter
“Omnis cellula e cellula”
November 9, 2018

14. The Complete Cell Theory
Putting it all together:
The 3 Basic Components of the Cell Theory were now complete:
1. All living things are composed of one or more cells. (Schleiden & Schwann, )
2. The cell is the basic unit of structure and function in all living things (Schleiden & Schwann, )
3. All cells come from preexisting cells (Virchow, 1858)
November 9, 2018

15. Two Basic Types of Cells
Prokaryotes
Single-celled.
Reproduce by binary fission (another copy by dividing).
No cell nucleus or any other membrane-bound organelles. DNA travels openly around the cell.
All bacteria are prokaryotes.
Images: Prokaryotic Cell, Eukaryotic cell , M. Ruiz
From the Virtual Cell Biology Classroom on ScienceProfOnline.com 15

16. Two Basic Types of Cells
Eukaryotes
Most organisms that we can see, such as trees, grass, worms, flies, mice, humans, mushrooms and yeast are eukaryotes.
Can either be single-celled or multi-celled.
Can reproduce in one of several ways (Ex. meiosis, mitosis).
Have cell nucleus within containing its DNA.
Nucleus most evident distinction between these cell types.

17. Prokaryotes vs. Eukaryotes
Notice the difference in complexity!
November 9, 2018

18. Lab Time !!! We will be looking at some prokaryotes.
Live active cultures from yogurt
Some prepared slides of prokaryotic cells
Follow the directions to prep the culture and draw what you see through the microscope
Look at the prepared slides and sketch what you see being sure to label what type of cell you are looking at.
If you are waiting to use the microscope, answer the worksheet on prokaryotes to be turned in at the end of class.
November 9, 2018