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Unit 4: Cells Part 2-Transport (Ch.7)

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James Planey

on 7 January 2013

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Transcript of Unit 4: Cells Part 2-Transport (Ch.7)

Passive Transport Movement of material from [High] to [Low]
No energy required Chemistry must be Considered A Free Ride Diffusion: The passive transport of molecules across a semi-permeable membrane Osmosis: The Diffusion of water (opposite direction to solute) Movement of material from [Low] to [High]
Energy is required Transport Things Spread Out Active Transport All other things being equal: * This is a consequence of the second law of thermodynamics, which says that the entropy of a system will increase unless energy is added to that system.

Locally energy is added in to living systems.

Globally, no energy is added to the net total energy of the Universe. A "Messy Room" on 2 different scales To Cancel Tonicity is Important Must Use A Protein! (Why?) Bulk Transport Endocytosis Exocytosis Big Questions How does the cell control what is transported at the cell membrane?

Why is transport of materials between the cell and its environment necessary for life?

How does the environment influence living systems?

How do cells exist within the confines of the Laws of Thermodynamics? Diffusion is inescapable (as long as you can fit through the membrane). Diffusion is an emergent & inescapable property of large concentrations of constantly moving molecules What can diffuse through the bi-layer? What does all the other stuff do? Transport Proteins! aquaporins and ion channels Channels and Carrier proteins control the diffusion of charged and polar molecules How can you "control" diffusion? Water What's Happening Here? What's Happening Here? The Sodium Potassium Pump: Can't Have A Nervous System Without Them! ATP Fills The Energy Reqirement Phosporylation Triggers a Conformational Change! Tonicity is a relative measure of solution concentration
The tonicity of a cell's environment has serious consequences for the cell Tonicity as it effects plant and animal cells.
Explain all situations shown! Circles indicate homeostatic condition Which way does sucrose go?
What if it can't? The contractice vacuole of a paramecium is an adaptation for living in an environment that is hypotonic compared to the cell Different osmoregulatory adaptations in salt-water and fresh-water fish vs. Moving Big Stuff Intake of large molecules.
more specialized. "Cell eating" "Cell drinking" "Cell being picky" Release of large cellular products into outflow Remember Me? Any Questions? A "Phagocyte" Make Sure You Can Explain how the consequences of the second law of thermodynamics allow diffusion to occur in the universe without an input of energy.

Compare passive and active transport.

Compare facilitated and simple diffusion.

Compare diffusion of a solute with osmosis of water.

Determine the tonicity relationships when given the concentrations of solutes of multiple solutions.

Predict the movement of specific molecules when given information about their relative concentrations and the characteristics of a given semi-permeable membrane.

Explain why animals and plants have evolved adaptations to survive in solutions of different toncities.

Predict the effect of altering tonicity on a plant or animal cell.

Compare exocytosis and endocytosis.

Explain the purposes and processes of the different modes of endocytosis employed by the cell. What you will learn in college
(not necessarily how you will learn it) Cotransport! The Cell Membrane Structure: Functions: The "Fluid Mosaic Model": A phospholipid bi-layer with associated proteins Boundary of cell
Transport of materials in and out of the cell
Communication between cell and environment Cholesterol: Structure: a steroid lipid Function: acts as a "temperature buffer" to help maintain membrane fluidity over a range of temperatures Membrane Proteins: Structure: Various, depending on the role they play:
Integral proteins: penetrate one or both layers of the bi-layer.
Peripheral proteins: associated with the membrane, but don't penetrate the bi-layer.
The polarity of different regions of a membrane protein vary according to the role of that protein. Functions: Many and more. Here's brief overview: Spotlight: Membrane Receptors Structure: Integral proteins that span the bi-layer with regions ("domains") that extend extra- and intra-cellularly. Function: Signal Transduction: The receipt of chemical messages from the environment and the relay (transduction") of those messages into the cell for response. Spotlight: Glycoproteins Structure: Integral proteins that span the bi-layer with short polysaccharide residues projecting extra-cellularly into the environment Function: Cell-Cell Recognition: Glycoproteins serve as an identifying marker in cellular populations (like your body). Membrane receptors are exploited by viruses (how?) Glycoproteins are a complication for organ transplants (why?) Lipids with a phosphate attached to glycerol in place of a fatty acid tail.
Polar (hydrophilic) phosphate "head", nonpolar (hydrophobic) fatty acid tails.
Spontaneously organizes in the presence of water to form a bi-layer
Fluid: phospholipids are constantly moving Structure: Function: Membrane Phospholipids: Makes a "selectively permeable" membrane. Only small, non-polar molecules can easily move through the phosopholipid bi-layer (Why?) membrane proteins are mobile in the cell membrane:
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