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Biology
Chapter 5*
19
Biology
Undergraduate 1
09/19/2010

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Term
Membrane Functions
Definition
1. Isolate cell content from the external environment
2. Regulate the exchange of essential substances
3. Allow communications between cells
4. Create attachments in and between cells
5. Regulate biochemical reactions
Term
Membrane Composition
Definition
Lipids and proteins
Term
Lipids
Definition
Phospholipids form a bilayer with hydrophilic heads and hydrophobic tails (with more saturated phospholipids are more fluid) (with more cholesterol are less fluid)
Term
Proteins
Definition
May be attached to membrane by a hydrophobic group. May be embedded in membrane. Many are glycoproteins (protein with a carbohydrate attached.
Term
Receptor Proteins
Definition
Receive and respond to messages from outside the cell
Term
Recognition Proteins
Definition
Glycoproteins with carbohydrates, on the outside of the membrane, cell specific
Term
Enzymatic Proteins
Definition
Promote chemical reactions
Term
Attachment Proteins
Definition
Anchored to cytoskeleton or extra cellular matrix or to other cells
Term
Transport Proteins
Definition
1. Channel proteins = form a channel/ pore that selectively allows molecules to get through
2. carrier proteins = bind to and carry molecules across the membrane
Term
Singer Nicolson Model
Definition
Cell membranes are viewed as two-dimensional solutions of oriented globular proteins and lipids
Term
Movement Across Membrane
Definition
Two Types = passive transport and energy-requiring transport
Term
Passive Transport
Definition
Diffusion of molecules or ions across membrane down a concentration gradient (high>low)
-Simple diffusion
-Facilitated diffusion
-Osmosis
Term
Simple Diffusion
Definition
Very small molecules with no net charge
Term
Facilitated Diffusion
Definition
Hydrophilic molecules (ions/polar molecules)
Channel proteins - selectivity for shape and charge of what they allow through the pore
Carrier protein - endose protein to allow to go through / can change its shape to allow different proteins through
Term
Osmosis
Definition
Diffusion of water across a selectively permeable membrane from a high concentration gradient to low (simple diffusion/facilitated by aquaporin channels)
Term
Energy-Requiring Transport
Definition
Movement of molecules or ions across membrane agains concentration gradient (low>high)
1. Active Transport
2. Endocytosis
3. Exocytosis
Term
Active Transport
Definition
Requires a protein that spans the membrane, a binding site specific to the molecule, and a binding site for energy carrier such as ATP
Term
Endocytosis
Definition
Engulfed by membrane into the cell.
-Pinocytosis = liquids into cell
-Receptor-mediated endocytosis = receptor based molecules into cell
-Phagocytosis = engulfing large particles
Term
Exocytosis
Definition
Out of the cell.
Membrane bound vesicles fused with a plasma membrane.
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