Transcript 5.1 Cell Theory - Grade10ScienceISZL

CELL THEORY
A Brief History
Robert Hooke named the cell [1665] based on observations of the
cell walls of cork tissue
Anton van Leeuwenhoek documented unicellular organisms based
on observations of protozoa [1673] and bacteria [1683]
Paramecium - Protocista
Amoeba - Protocista
Matthias Schleiden proposed that cells were the fundamental units
of plants based on observations of plant tissue [1838]
Plant cells
t Cell
Theodor Schwann proposed that cells were the fundamental units
of animals based on observations of animal tissue [1839]
Blood
Sperm
Schleiden and Schwann are credited as the founders of 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 development of the Cell Theory involved the input of numerous
individuals from various nationalities over many years
Rudolph Virchow stated “omnis cellula a cellula ” [all cells arise
from pre-existing cells based on observations of dividing cells
[1855]
Rudolph Virchow stated “omnis cellula a cellula ” [all cells arise
from pre-existing cells based on observations of dividing cells
[1855]
The Cell Theory was modified to incorporate Virchow’s work
 All organisms are made of cells
 Cells are the smallest structural and functional unit of an
organism [that carries out the life processes]
 All cells come from pre-existing cells
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)
SO:
 Could there be an organism that does not contain a single cell?
 Might there be some other fundamental unit of life? At least, in
some cases?
 Are the life processes sufficient criteria to distinguish between
the living and the non-living?
Microscopes
Max magnification – X1000
Max Resolution 0.2um
Max magnification X1000,000
Max Resolution 0.5nm
Microscopic measurements
mm – millimeters
μm – micrometer
nm - nanometers
1m = 1000mm = 1000,000μm= 1000,000,000nm
Comaparison of Light and Electron
Microscopes
Light Microscope
Human Cheek Cell
Nerve Cells
Transmission Electron Microscope
Plant Cell
Mitochondrion
Scanning Electron Microscope
Human Sperm
Insect Head
Sizes of Biological Structures
 Thickness of leaf
 O.5mm
 Paramecium
 200μm
 Sharp end of pin
 100 μm
 Plant cell
 40μm
 Animal cell
 20μm
 Mitochondrion
 1μm
 Bacterium
 0.5-1μm
 Ribosome
 20nm
 DNA molecule
 2nm
 Hydrogen atom
 0.04nm
Red and White Blood Cells
 S.E. M
Light Microscope