a selectively permeable phospholipid bilayer that surrounds all cells. the cell membrane is …
TRANSCRIPT
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a selectively permeable phospholipid bilayer that
surrounds all cells.
The Cell membrane is …
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Selectively Permeable
• It chooses or selects specific substances
Permeable means to pass pass through
A selectively permeable membrane is selective about what it allow to pass through
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Cell membrane diagram
Inside
cell
Outside cell
Cell membrane
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Polarity• Polar: has opposite charges
at opposite ends of molecule
* Example: Water
Non-polar: Balanced molecule with charges evenly spaced around molecule
* Example: fats and oils
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Phospholipid diagrams
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Outside cell
Inside cell
A picture of the cell membrane using a transmission election microscope
T.E.M.
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Membrane proteins are imbedded in plasma membrane.
Outside cell
Inside
cell
nucleus
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Organelles are surrounded by membranes!
Golgi Apparatus
Lysosomes
Mitochondria
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Membrane proteins do the following 4 things
1) Recognition proteins: Identify the cell! (recognize the cell)
2) Receptor proteins: React to stimulation and cause cell to function (react).
3) Transport Proteins: transport substances across plasma membrane.
4) Enzymes: Catalyze reactions on membrane surface
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Recognition Proteins
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Passive Transport
• Not requiring energy or ATP
• When substances diffuse from a high to a low concentration
• When they diffuse down their concentration gradient
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Types of Transport Proteins
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Facilitated Diffusion: a passive form of transport using membrane proteins
Before After
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Active Transport
• Requires Energy or ATP
• When something large or difficult needs to pass through the membrane
• When substances have to be pushed or “pumped” backwards from a low to a high concentration.
• Proteins that do this are called protein pumps
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Active transport
Adapted from Campbell, Reece & Mitchell, Biology 6 th edition, 2002with permission of Pearson Education, Inc.
1 2
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Active transport (cont.)
Adapted from Campbell, Reece & Mitchell, Biology 6 th edition, 2002with permission of Pearson Education, Inc.
3 4
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Active transport (cont.)
Adapted from Campbell, Reece & Mitchell, Biology 6 th edition, 2002with permission of Pearson Education, Inc.
5 6
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Endocytosis: when the cell membrane must move to engulf larger
substances that cannot fit through
• There are 3 different types that will be discussed
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Phagocytosis: when very large substances are engulfed into the cell. (pac-man)
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Pinocytosis• Same as phagocytosis but with smaller
substances and liquids
• “cell slurping”
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Exocytosis• When substances leave the cell (saliva,
sweat, oils, digestive juices, tears)
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• The same cell is a hypertonic environment will loose water, shrivel, and probably die.
• A cell in a hypotonic solution will gain water, swell, and burst.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 8.12