2/18/2013 1 THE CELL History of the microscope and cell 1500’s: Europe Merchants used magnifying glasses to determine quality of cloth Mid 1600’s: Holland, development of the microscope and telescope 1665: Robert Hooke (English) ** first to observe DEAD CELLS 1675: Anton van Leeuwenhoek (Dutch) ** first to observe LIVING CELLS History, cont. 1833: Robert Brown (Scottish) Discovered nucleus 1838: Matthias Schleiden (German) Stated “all plants are made of cells” 1839: Theodor Schwann (Dutch) Stated “all animals are made of cells” 1855: Rudolf Verchow (German MD) Stated “all cells arise from other cells” Characteristics of Microscopes • magnification: ability to make an image larger than actual size • resolution: power to show details clearly while enlarged (if poor, objects seem fuzzy) Types of Microscopes I. compound light - light passes through one or more lenses - object must be sliced thinly enough to be transparent - upper limitation is 2000X or 0.5 microns (um) in diameter II. Electron Microscopes - limited by physical characteristics of light - can magnify an image up to 200,000 X, or 2 nm in diameter - beams of electrons produces enlarged image
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THE CELL Bio PPT slides/cell.pdf · molecules to pass across the membrane animation – permeability animation – fluid mosaic Membrane Proteins 1. transport proteins: - involved
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2/18/2013
1
THE CELL
History of the microscope and cell
1500’s: Europe
Merchants used magnifying glasses to determine quality of cloth
Mid 1600’s: Holland, development of the microscope and telescope
1665: Robert Hooke (English)
** first to observe DEAD CELLS
1675: Anton van Leeuwenhoek (Dutch)
** first to observe LIVING CELLS
History, cont. 1833: Robert Brown (Scottish)
Discovered nucleus
1838: Matthias Schleiden (German)
Stated “all plants are made of cells”
1839: Theodor Schwann (Dutch)
Stated “all animals are made of cells”
1855: Rudolf Verchow (German MD)
Stated “all cells arise from other cells”
Characteristics of Microscopes
• magnification: ability to make an image larger than
actual size
• resolution: power to show details clearly while enlarged
(if poor, objects seem fuzzy)
Types of Microscopes
I. compound light
- light passes through one or more lenses
- object must be sliced thinly enough to be transparent
- upper limitation is 2000X or 0.5 microns (um) in diameter
II. Electron Microscopes
- limited by physical characteristics of light
- can magnify an image up to 200,000 X, or
2 nm in diameter
- beams of electrons produces enlarged
image
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Types of Electron Microscopes
1. transmission electron microscope (TEM)
- transmits a beam of electrons
through very thinly sliced specimen
- dead specimens
- 200,000 X magnification
- black and white only
Plant Cell
2. scanning electron microscope (SEM)
- three dimensional images
- beam of electrons passed over specimens surface
- 100,000 X mag.
- dead specimens only
3. scanning tunneling microscope
- computer tracks movement of probe across object
- produces 3 D images
- can be used on living organisms
CELL THEORY
1. all living things are composed of cells
2. cells are basic units of structure and
function
3. all cells come from pre- existing cells
How cells differ
1. size
- most cells are 5-50 microns
surface area ratio (limits size of cells)
inside of cell grows faster: cubed
(V = L x W x H)
outside of cell grows slower: squared
(A = L x W)
Relationship of Surface Area to Volume
LENGTH OF
SIDE
(CM)
TOTAL
SURFACE
AREA (CM2)
TOTAL
VOLUME
(CM3)
SURFACE
AREA TO
VOLUME
RATIO
1
(1X1X6)= 6
(1X1X1)=1
6:1
2
(2X2X6)=24
(2X2X2)=8
24:8
3:1
3
(3X3X6)= 54
(3X3X3)=27
54:27
2:1
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2. shape
- most spherical or cuboidal
- different shapes reflect function
dermal epidermal cells
white blood cells
goblet cell
red blood cells
nerve cell
3. internal organization
- organized by nucleus and organelles
- 2 types cells
1. prokaryotes:
- no nucleus or membrane
bound organelles
- more primitive cells
(bacteria)
- no compartments within
cytoplasm so ribosomes,
enzymes, DNA free floating
- contain cell walls- made of peptidoglycans
(polysaccharides connected by short chains of a. a. )
- flagella: whiplike structures for movement
Types of cells, cont.
2. eukaryotes:
- contain nucleus and membrane
bound organelles
- unicellular eukaryotes have
flagella or cilia for movement
- much more complex cells
Common features of all cells
- cell membrane (plasma membrane)
- cytoplasm: gel like , holds cellular structures
- cytoskeleton: microscopic protein fibers that keep cells shape
- ribosomes: make proteins
- DNA: controls all cell activities
CELL STRUCTURE
Main components of eukaryotic cells
1. cell membrane (outer boundary)
2. nucleus (control center)
3. cytoplasm (material between nucleus
and membrane)
ANIMAL CELLS
Cell Membrane
(plasma membrane)
Functions:
- separates cells from surroundings
- regulates substance movement
(bring in nutrients, remove wastes)
- selectively permeable
- protection and support
- gives shape and flexibility
- signal receptor from other cells
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Fluid mosaic model of Cell Membrane
liquid phospholipid bilayer (water insoluble, no movement through)
- polar outside (head- phospholipid, hydrophilic)
- nonpolar inside (tail- two fatty acids, hydrophobic)
- polar outside (head- phospholipid, hydrophilic)
Polar: hydrophilic; attracts other polar and ionic compounds
Non-polar: hydrophobic; will not allow most polar molecules, ions, or large
molecules to pass across the membrane
animation – permeability animation – fluid mosaic
Membrane Proteins 1. transport proteins:
- involved in facilitated diffusion
(water soluble mols. not soluble in fat portion of membrane, so need help)
- go through the entire membrane
2 types
channel: gated pores
move water and ions freely in and out of cell
carrier: substrate binds to site on protein
protein changes shape and exposes substrate to cytoplasm
2. recognition proteins: recognizes substances
(like tips of icebergs emerging from ocean surface)
- Contain carbohydrate antennas (glycoproteins)
- Used as chemical ID markers to differential cell types
***cell/cell recognition (immune response)
***embryo cells tissues organ systems
3. receptor proteins: binds to specific molecules
(neurotransmitters, blood antigens, hormones)
- initiates cell response
4. enzymes: embedded in cell membrane to catalyze biochemical
reactions in cell
called FLUID MOSAIC because:
lipids and protein are liquid in nature and can move around each other
membrane is DYNAMIC (always changing)
Nucleus
- control center of cell: directs all cell activities