PGS. 168 - 199

ANTON VAN LEEUWNENHOEK
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One of the first person ’ s to use a microscope.
Looked at pond water and saw small organisms.

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1.
All living things are composed of cells.
2. Cells are the basic unit of structure & function in living things.
3. New cells are produced by existing cells.

Cells are the basic unit of life.
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Microscopy Today: Compound Light
Microscope
 Light passed through specimen
 Focused by glass lenses
 Image formed on human retina
 Max magnification about 1000X
 Resolves objects separated by 0.2 m m, 500X better than human eye
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Compound Light Microscope
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
amoeba, light micrograph eye ocular lens light rays
85 µm objective lens specimen condenser lens light source a. Compound light microscope
© Robert Brons/Biological Photo Service
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Microscopy Today: Transmission
Electron Microscope
 Abbreviated T.E.M.
 Electrons passed through specimen
 Focused by magnetic lenses
 Image formed on fluorescent screen
 Similar to TV screen
 Image is then photographed
 Max magnification 1000,000sX
 Resolves objects separated by 0.00002 m m,
100,000X better than human eye
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Transmission Electron Microscope
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
200 nm pseudopod segment, transmission electron micrograph electron source electron beam electromagnetic condenser lens specimen electromagnetic objective lens electromagnetic projector lens observation screen or photographic plate b. Transmission electron microscope
© M. Schliwa/Visuals Unlimited
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Microscopy Today: Scanning
Electron Microscope
 Abbreviated S.E.M.
 Specimen sprayed with thin coat of metal
 Electron beam scanned across surface of specimen
 Metal emits secondary electrons
 Emitted electrons focused by magnetic lenses
 Image formed on fluorescent screen
 Similar to TV screen
 Image is then photographed
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Scanning Electron Microscope
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
amoeba, scanning electron micrograph electron gun electron beam electromagnetic condenser lenses scanning coil final condenser lens secondary electrons specimen electron detector
TV viewing screen c. Scanning electron microscope
© Kessel/Shih/Peter Arnold, Inc.
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Microscopy and Amoeba proteus
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
amoeba, light micrograph
85µm 200 nm pseudopod segment, transmission electron micrograph
500µm amoeba, scanning electron micrograph eye ocular lens light rays electron source electron beam electron gun electron beam electromagnetic condenser lens electromagnetic condenserl enses specimen electromagnetic objective lens objective lens specimen condenser lens electromagnetic projector lens observation screen or photographic plate b. Transmission electron microscope scanning coil final
Condenser lens secondary electrons specimen light source a. Compound light microscope a: © Robert Brons/Biological Photo Service; b: © M. Schliwa/Visuals Unlimited; c: © Kessel/Shih/Peter Arnold, Inc.
electron detector
TV
Viewing screen c. Scanning electron microscope
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Cells are the basic unit of life.
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1. PROKARYOTE: do not contain a membrane bound nucleus
(all bacteria are prokaryotes)
2. EUKARYOTE: DO contain a membrane bound nucleus, and most have other specialized organelles.

Main Idea: The plasma membrane helps to maintain a cell’s homeostasis.
Essential Questions:
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How does a cell’s plasma membrane function?
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What are the roles of proteins, carbohydrates, and cholesterol in the plasma membrane?

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Separates cells from the watery environment
Maintain homeostasis – the process of maintaining balance in an organism’s internal evnrionment
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How does it do this?
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Selective permeability – a property of the plasma membrane that allows some substances to pass through while keeping others out.

Cell membrane is selectively permeable & provides protection & support
Small particles move more easily than large particles
Neutral molecules more easily than charged ions
Non polar more easily than polar
Substances that move across the cell membrane can vary from cell to cell, or the same cell from moment to moment
Major component of the cell membrane is a lipid bilayer
Proteins & carbohydrates are also found in the cell membrane

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Found in plants, algae, fungi, and nearly all prokaryotes.
MAIN FUNCTION: provide support & protection for the cell
Animal cells DO NOT have cell walls!

Maintaining Homeostasis
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All cells must regulate what materials enter & leave; sometimes no energy is required to do this, other times energy is required
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Passive transport – no energy is required to move substances from an area of high concentration to an area of low concentration

Types of Passive Transport
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Diffusion – the movement of a solute from an area of high conc.
To an area of low conc. Equilibrium is reached when an equal number of molecules move in both directions

Types of Passive Transport
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Osmosis – the diffusion of water across a membrane from a region of high water concentration to a region of low water concentration http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion
_works.html

Types of Passive Transport
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Facilitated diffusion – process by which transport proteins carry certain molecules across a membrane from high concentration to low concentration

Types of Osmotic Solutions
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Isotonic solution
– solution has the same solute concentration as that of the living cell, there is no net movement of H
2
O

Types of Osmotic Solutions
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Hypertonic solution – solution has a higher solute concentration than the inside of the cell; H
2
O moves out of the cell; animal cell will shrink
(crenate); vacuole collapses in plant cells

Types of Osmotic Solutions
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Hypotonic solution – solution has a lower solute concentration than the inside of the cell; H
2
O moves into the cell; animal cell will burst (lyse); plant cell will not
(why?)

Types of Osmotic Solutions http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter21/animation__hemolysis_and
_crenation.html
(animation of isotonic, hypertonic, hypotonic solutions)

Types of Osmotic Solutions

Active Transport
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Energy is required to move substances from an area of low concentration to an area of high concentration; allows cells to have internal environments that are different chemically from the external environment

Types of Active Transport
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Molecular transport - proteins in the cell membrane work as “ pumps ” to move substances against the concentration gradient

Types of Active Transport
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Endocytosis - process by which a cell takes material into the cell by infolding of the cell membrane
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Phagocytosis – large particles taken in
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Pinocytosis – H
2 in
O or small particles are taken
Exocytosis – process by which cell releases large amounts of material; vacuole membrane fuses with the cell membrane

Types of Active Transport
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