Cell Theory Prokaryotes & Eukaryotes

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

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: 100 - 350 micrometers Size: 100 - 350 micrometers November 9, 2018

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

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

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

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

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

Spontaneous Generation???? Next 150 - 200 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

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

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

Schleiden and Schwann 1838 - 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

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

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, 1838-39) 2. The cell is the basic unit of structure and function in all living things (Schleiden & Schwann, 1838-39) 3. All cells come from preexisting cells (Virchow, 1858) November 9, 2018

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

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.

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

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