4-1 Introduction to the Cell. Important events in the discovery of the cell and the development of...
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Transcript of 4-1 Introduction to the Cell. Important events in the discovery of the cell and the development of...
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
1855 - Rudolph Virchow
A physician who did
research on cancer cells and concluded
“Omnis cellula e cellula”.
“All cells are from other
pre-existing cells.”
The Cell Theory
1. 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.
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 Types
Prokaryotes- simple cells that do not have internal membranesexample = bacteria
Eukaryotes- more complex cells that do have internal, membrane-bound structuresexamples = plants and animals
Timeline
Prokaryotic
Organisms:
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