The Development of the Cell Theory Cell Biology Prepared by: A. Abougabal

Timeline of the discoveries, thoughts and technologies that led to the development of the Cell Theory 500 BCE 1000 1600 1800 300 BCE 1500 1700 1900 Ancient Times Ancient peoples are always on the look-out for ways that organisms can be used by them. Some civilizations support “great thinkers” and philosophers, but they rarely base their thoughts on observation or experiments.

Greek philosopher, Aristotle, begins to observe nature. Timeline of the discoveries, thoughts and technologies that led to the development of the Cell Theory 500 BCE 1000 1600 1800 300 BCE 1500 1700 1900 334 B.C.E - Aristotle Greek philosopher, Aristotle, begins to observe nature. He classifies all known organisms as either a Plant or and Animal. He writes that living things can arise spontaneously from non-living matter.

Timeline of the discoveries, thoughts and technologies that led to the development of the Cell Theory 500 BCE 1000 1600 1800 300 BCE 1500 1700 1900 1268 – 1st Eyeglasses Roger Bacon, an English friar makes reference to a pair of eye glasses. This means that glass is being developed and used in a way that makes it easier to see small things.

Timeline of the discoveries, thoughts and technologies that led to the development of the Cell Theory 500 BCE 1000 1600 1800 300 BCE 1500 1700 1900 1590 – 1st Microscope Zacharias Janssen, a Dutch eyeglass maker, makes the 1st microscope by placing two lenses on top of one another to make extra-large images.

1600’s People start to question the origins of life. Timeline of the discoveries, thoughts and technologies that led to the development of the Cell Theory 500 BCE 1000 1600 1800 300 BCE 1500 1700 1900 1600’s People start to question the origins of life. Many begin to suggest that life can only come from other forms of life rather than through spontaneous generation (as was suggested by Aristotle). This only took about 2000 years! William Harvey says that maggots do not come from the meat itself but from tiny eggs too small to be scene. William Harvey English Physician 1578-1657

Cell Theory and the Scientists Who Helped Shape It

“Father of microscopy.” Timeline of the discoveries, thoughts and technologies that led to the development of the Cell Theory 500 BCE 1000 1600 1800 300 BCE 1500 1700 1900 1674 – 1st Microscopic Beasties Seen! Anton van Leeuwenhoek (1632-1723) reports being able to see tiny beasties (0.002 mm) using a simple single-lens microscope. He is known as the “Father of microscopy.”

Anton van Leeuwenhoek he documented unicellular organisms based on observations of protozoa [1673] and bacteria [1683]

Robert Hooke microscopy” Born: July 18, 1635 Died: March 3, 1703 Wrote and published “Micrographia” Known as the “English Father of microscopy” http://www-groups.dcs.st-and.ac.uk/~history/PictDisplay/Hooke.html

Robert Hooke Contributions: [1665] He observed pieces of cork from the bark of a cork tree under the microscope. His observations led him to coin the word “cell.” -“Cell” means little rooms in Latin http://www.learner.org/channel/courses/essential/life/session1/closer1.html

The beginning of the end of spontaneous generation! Timeline of the discoveries, thoughts and technologies that led to the development of the Cell Theory 500 BCE 1000 1600 1800 300 BCE 1500 1700 1900 1667 – Species Defined John Ray (1627-1705) defines a “species” as a set of individuals that can reproduce their own kind. The beginning of the end of spontaneous generation! William Harvey English Physician 1578-1657

1668 – 1st Experiments about origins of maggots Timeline of the discoveries, thoughts and technologies that led to the development of the Cell Theory 500 BCE 1000 1600 1800 300 BCE 1500 1700 1900 1668 – 1st Experiments about origins of maggots Francesco Redi (1626-1697) conducts experiments to prove that maggots do not appear in meat if flies cannot land on it! William Harvey English Physician 1578-1657

Timeline of the discoveries, thoughts and technologies that led to the development of the Cell Theory 500 BCE 1000 1600 1800 300 BCE 1500 1700 1900 1700’s Microscope claimed to be an instrument of evil when a prominent person was horrified by the sight of a magnified flea! Scientists begin to doubt spontaneous generation, but the common people still believe in it!

1770 – Advancement of microscopes Timeline of the discoveries, thoughts and technologies that led to the development of the Cell Theory 500 BCE 1000 1600 1800 300 BCE 1500 1700 1900 1770 – Advancement of microscopes Microscopes become sturdier and easier to use. Flaws in glass production still causes images to be blurry and have coloured halos.

1809 – 1st Science Texts for Students Timeline of the discoveries, thoughts and technologies that led to the development of the Cell Theory 500 BCE 1000 1600 1800 300 BCE 1500 1700 1900 1809 – 1st Science Texts for Students Jane Haldimand (1769-1858) writes textbooks for young people to learn about science. Terms such as “cell”, “cellular system” and “Cellular tissue” appear in the book.

1825 – Book “Cells from Cells” Timeline of the discoveries, thoughts and technologies that led to the development of the Cell Theory 500 BCE 1000 1600 1800 300 BCE 1500 1700 1900 1825 – Book “Cells from Cells” Francois Vincent Raspail (1794-1878) wrote a book called (translated from Latin) “Every cell is derived from a pre-existing cell”.This again puts to rest the idea of spontaneous generation.

Scientists begin to study the cell extensively! Timeline of the discoveries, thoughts and technologies that led to the development of the Cell Theory 500 BCE 1000 1600 1800 300 BCE 1500 1700 1900 1830 – Cells are studied Biology is becoming an important science and the body of knowledge is growing, especially since the improvement of microscopes. Scientists begin to study the cell extensively!

Timeline of the discoveries, thoughts and technologies that led to the development of the Cell Theory 500 BCE 1000 1600 1800 300 BCE 1500 1700 1900 1831 – Nucleus of Cell Found Robert Brown (1773-1858) is the 1st to consider the nucleus as a regular part of a living cell. The nucleus is still hard to see though without the invention of the electric light for his microscope.

Timeline of the discoveries, thoughts and technologies that led to the development of the Cell Theory 500 BCE 1000 1600 1800 300 BCE 1500 1700 1900 1838 – Plant cells! Matthias Jacob Schleiden (1804-1881) makes the claim “All plants are made of cells”. Cells are alive!

“All living things are made of cells” Timeline of the discoveries, thoughts and technologies that led to the development of the Cell Theory 500 BCE 1000 1600 1800 300 BCE 1500 1700 1900 1839 – Animal cells! Theodor Schwann (1810-1882) makes the claim “All animals are made of cells”. “All living things are made of cells” Cells are the basic building blocks of life!

“The cell is the basic unit of life”. Timeline of the discoveries, thoughts and technologies that led to the development of the Cell Theory 500 BCE 1000 1600 1800 300 BCE 1500 1700 1900 1845 – Cell Basic Unit of Life Alexander Carl Heinrich Braun (1805-1877) makes the claim: “The cell is the basic unit of life”. Cells are made of protoplasm enveloped by a flexible membrane.

1860’s, The end of the “Spontaneous Generation” debate Timeline of the discoveries, thoughts and technologies that led to the development of the Cell Theory 500 BCE 1000 1600 1800 300 BCE 1500 1700 1900 1860’s, The end of the “Spontaneous Generation” debate Louis Pasteur (1822-1895) conducts a series of experiments that once and for all put to rest the idea of spontaneous generation and concluding that living organisms do not arise from non-living matter.

Who came up with the theory?

Major Contributors: Matthias Schleiden Theodor Schwann Rudolph Virchow

1-Rudolph Virchow German pathologist He is known as the “Father of Pathology.” Born: October 13, 1821 Died: September 5, 1902

All cells come from pre-existing cells! Timeline of the discoveries, thoughts and technologies that led to the development of the Cell Theory 500 BCE 1000 1600 1800 300 BCE 1500 1700 1900 Rudolph wirchow stated “omnis cellula a cellula ” [all cells arise from pre-existing cells based on observations of dividing cells [1855] All cells come from pre-existing cells! Cell Theory that is still largely accepted today. Virchow

All plants are made of cells! proposed that cells were the fundamental units of plants based on observations of plant tissue [1838] All plants are made of cells! 2. Schleiden (1838) German botanist Born: April 5, 1804 Died: June 23, 1881 Onion skin cells

Plant cells

Who came up with this theory? proposed that cells were the fundamental units of animals based on observations of animal tissue [1839] All animals are made of cells! 3. Schwann German zoologist Born: December 7, 1810 Died: January 11, 1882 / Human red blood cells

Blood

Sperm

Schleiden and Schwann The Cell Theory [1839] All living things are made of cells. Cells exhibit the fundamental characteristics of life: Obtain energy—photosynthesis, chemosynthesis, or digestion Use energy—respire Excrete Waste Show Order Homeostasis Evolve Reproduce Move Respond to changes in environment Grow and repair damage to self

The Cell Theory States: As written by Rudolph Virchow (1821-1902): All living organisms are made of one or more cells. Cells are the basic units of structure and function in all organisms. All cells come from previously existing cells. The activity of an entire organism depends on the total activity of its independent cells.

Definition = Three part theory about cells 1. All living things are made of cells.

Part 2 of the Theory 2. The cell is the basic structural and functional unit of life.

Part 3 of the Theory 3. All cells come from pre-existing cells. yeast cells dividing

How big are cells? Microscopic (mostly) Measured in microns µm (micrometers). A µm is one millionth of a meter = 10-9 m = one thousandth of 1 mm.

How big are cells? Smallest free-living cell = Mycoplasma genitalium Size = 0.2 to 0.3 µm

Bacteria e.g. Eschericia coli (aka E.coli) How big are cells? Bacteria e.g. Eschericia coli (aka E.coli) Size=1 µm by 3 µm

How big are cells? Human red blood cell = 8 µm in diameter

Largest cell on the human body = ovum How big are cells? Largest cell on the human body = ovum Size= 1000 µm in diameter (1 mm)

How big are cells? Smallest cell in the human body = sperm cell.

How can we study cells? Problem: They are microscopic! Solution: Use a microscope!

Cell biology Cell biology is the study of cell structure and function, and it revolves around the concept that the cell is the fundamental unit of life. Focusing on the cell permits a detailed understanding of the tissues and organisms that cells compose. Some organisms have only one cell, while others are organized into cooperative groups with huge numbers of cells. On the whole, cell biology focuses on the structure and function of a cell, from the most general properties shared by all cells, to the unique, highly intricate functions particular to specialized cells.

Microscopes

A. COMPOUND MICROSCOPE Compound light microscope Light passes through lenses to magnify image up to 1000X Can observe living cells

Light Microscope Nerve Cells Human Cheek Cell

B. STEREOMICROSCOPE Gives 3D images of specimen

C. SCANNING ELECTRON MICROSCOPE (SEM) Uses electrons instead of light to project surface image of specimen

SCANNING ELECTRON MICROSCOPE (SEM) Uses a beam of electrons to magnify image > 1000X Kills cells being observed

Scanning Electron Microscope Human Sperm Insect Head

D. TRANSMISSION ELECTRON MICROSCOPE (TEM) Works like light microscope except uses electrons

Transmission Electron Microscope Plant Cell Mitochondrion

Comaparison of Light and Electron Microscopes

Microscopic measurements mm – millimeters μm – micrometer nm - nanometers 1m = 1000mm = 1000,000μm= 1000,000,000nm

Assignment #1 which microscope can be used to study the following Sizes of Biological Structures Thickness of leaf Paramecium Sharp end of pin Plant cell Animal cell Mitochondrion Bacterium Ribosome DNA molecule Hydrogen atom O.5mm 200μm 100 μm 40μm 20μm 1μm 0.5-1μm 20nm 2nm 0.04nm

Thanks And That is the end

And, what about viruses? Are not composed of cells but consist of a nucleic acid (DNA or RNA) in a protein coat Yet conduct all of the cell processes (although with help, not independently)