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Good Morning 1 1/13
• Do Now : effects of acid sprayed tomato plants
• Take out notebook • Discuss size of a cell and why they
are the size that they are • Volume to surface area ratio –
activity
1
How Big is It? • http://www.cellsalive.com/howbig_js.htm
2
3
The Plasma Membrane -
Gateway to the Cell
Allows molecules to move in and out of the cell
What needs to get into and out of the cell?
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CO2 and Oxygen
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Blood cells take Oxygen and nutrients to every cell in the body and CO2 is removed
Wastes, Carbon dioxide and Urea pass out of cells
through membrane
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Cells are limited to size due to its
Volume to Surface area Ratio
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Photograph of a Cell Membrane
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Cell Membrane
The cell membrane is flexible and allows a unicellular organism to move
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Homeostasis
• Balanced internal condition of cells
• Also called equilibrium• Maintained by plasma
membrane controlling what enters & leaves the cell
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Functions of Plasma Membrane
Protective barrier
Regulate transport in & out of cell (selectively permeable)
Allow cell recognition
Provide anchoring sites for filaments of cytoskeleton
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Structure of the Cell Membrane
copyright cmassengale
14
Structure of the membrane is Made up of phospholipids, Proteins and cholesterol
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FLUID- because individual phospholipids and proteins can move side-to-side within the layer, like it’s a liquid.
MOSAIC- because of the pattern produced by the scattered protein molecules when the membrane is viewed from above
http://www.dnatube.com/video/360/Fluid-Mosaic-Model
FLUID MOSAIC MODEL
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Polar heads are hydrophilic “water loving”Nonpolar tails are hydrophobic “water fearing”
Cell Membrane
Makes membrane “Selective” in what crosses
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Cell Membrane
Hydrophobic molecules pass easily; hydrophilic DO NOT
The cell membrane is made of 2 layers of phospholipids called the lipid bilayer
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Small molecules and larger hydrophobic molecules move through easily.e.g. O2, CO2, H2O
Semipermeable or selectively permeable
Membrane
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Ions, hydrophilic molecules larger than water, and large molecules such as proteins do not move through the membrane on their own.
Semipermeable Membrane
http://www.bing.com/videos/search?q=Cell+Membrane+animation&go=Submit&qs=n&form=QBVR&pq=cell+membrane+animation&sc=8-23&sp=-1&sk=#view=detail&mid=7FC1F9FD1D31B1EAB2057FC1F9FD1D31B1EAB205
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Types of Transport Across Cell Membranes
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Passive TransportSimple Diffusion
Doesn’t require energy
Moves high to low concentration
Example: Oxygen or water diffusing into a cell and carbon dioxide diffusing out.
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Simple Diffusion
• Requires NO energy
• Molecules move from area of HIGH to LOW concentration
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DIFFUSION
Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY
Diffusion through a Membrane
Cell membrane
Solute moves DOWN concentration gradient (HIGH to LOW)
Solute= anything that is dissolved (in water)
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Diffusion of Liquids
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Passive TransportFacilitated diffusion
Doesn’t require energy
Uses transport proteins to move high to low concentration
Examples: Glucose or amino acids moving from blood into a cell.
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Active Transport
Requires energy or ATP
Moves materials from LOW to HIGH concentration
AGAINST concentration gradient
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Carrier Proteins• Other
carrier proteins change shape to move materials across the cell membrane
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Endocytosis – Phagocytosis
Used to engulf large particles such as food, bacteria, etc. into vesicles
Called “Cell Eating”
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Phagocytosis - Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue)
copyright cmassengale
32
Moving the “Big Stuff”
Molecules are moved out of the cell by vesicles that fuse with the plasma membrane.
Exocytosis-
moving things out.
This is how many hormones are secreted
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Exocytosis The opposite of endocytosis is exocytosis. Large molecules that are manufactured in
the cell are released through the cell membrane.
Inside Cell Cell environment
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Three Forms of Transport Across the Membrane
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Osmosis
• Diffusion of water across a membrane
• Moves from HIGH to Low
Diffusion across a membrane
Semipermeable
membrane
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Diffusion of H2O Across A Membrane
High H2O potentialLow solute concentration
Low H2O potentialHigh solute concentration
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Aquaporins• Water Channels• Protein pores used during
OSMOSISWATERMOLECULES
copyright cmassengale
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Cell in Isotonic Solution
CELL
10% NaCL90% H2O
10% NaCL
90% H2O
What is the direction of water movement?The cell is at _______________.equilibrium
ENVIRONMENT
NO NET MOVEMENT
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Cell in Hypotonic Solution
CELL
10% NaCL90% H2O
20% NaCL
80% H2O
What is the direction of water movement?
40
Cell in Hypertonic Solution
CELL
15% NaCL85% H2O
5% NaCL95% H2O
What is the direction of water movement?
ENVIRONMENT
Isotonic Solution
NO NET MOVEMENT OF
H2O (equal amounts entering
& leaving)
Hypotonic Solution
CYTOLYSIS- cell busts
Hypertonic Solution
PLASMOLYSIS- shriveling of cell
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Cytolysis & Plasmolysis
Cytolysis Plasmolysis
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Osmosis in Red Blood Cells
Isotonic Hypotonic
Hypertonic
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hypotonic hypertonic isotonic
hypertonic isotonic hypotonic