[ppt]the cell theory - ursuline high school · web view4-1 introduction to the cell important...
TRANSCRIPT
4-1 Introduction to
the Cell
Important events in the discovery of the
cell and the development of the
cell theory…..
1665 – Robert Hooke Observed cells in cork.Coined the term "cells”.
Cork Cells
1673- Anton van Leeuwenhoek
Created a powerful microscope
1827-33 - Robert Brown-noticed that pollen grains in water jiggled around
called “Brownian motion”-discovered the nucleus
Nucleus
Human Cheek Cell
1838 - Matthias SchleidenA botanist who concluded that all plants are made of cells.
Typical Plant Cell
1839 - Theodor SchwannA zoologist who concluded that all animals
are made of cells.
Nerve Cells
1855 - Rudolph Virchow
A physician who didresearch on cancer cells
and concluded“Omnis cellula e cellula”.
“All cells are from other pre-existing cells.”
The Cell Theory1. 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 existing cells.
Cells are Diverse…both in size, shape, and
internal organization.
Why Are Cells So Small?• Transport- Cell volume to surface
area ratios favor small size.• Control- Nucleus to cytoplasm
consideration.• Metabolic requirements- ……..we’ll come back to this later.
How small can a cell be?
Mycoplasmas - bacteria that are 0.1 to 1.0 m. (1/10 the size of regular
bacteria).
Note: 1.0 m = one millionth of a meter
All cells have……
• Plasma (cell) Membrane• Nucleus (eukaryotes only)• Cytoplasm (an area)• Organelles (structures with specialized functions)
Cell TypesProkaryotes- simple cells that do
not have internal membranesexample = bacteria
Eukaryotes- more complex cells that do have internal, membrane-bound structuresexamples = plants and animals
Timeline
ProkaryoticOrganisms:
First appeared 3.5 BYA
include bacteria and cyanobacteria
Eukaryotic Organisms:
First appeared 2.0 BYA
include protists, fungi, plants and
animals
Key Differences:Prokaryotes
• Lack a nucleus and other membrane bounded structures.
• Have small ribosomes• DNA is not organized
into chromosomes• Flagella are not made of
microtubules and does not have a 9+2 structure
• Cell walls are made of peptidoglycan, not cellulose
Eukaryotes• Have a nucleus and other
membrane bounded structures.
• Have large ribosomes• DNA is organized into
chromosomes • Flagella are made of
microtubules and have a 9+2 structure
• Cell walls are made of cellulose
Prokaryotic Eukaryotic
Nucleus
Examples
Prokaryotic
Eukaryotic