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Life Science I
A Closer Look at Membranes
23
Biology
Undergraduate 1
03/05/2011

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Term
Lipid Bilayer
Definition
main component of cell membranes
Term
gives membrane its fluid properties
Definition
lipid bilayer
Term
In the fluid mosaic model, the membrane is a mosaic of
Definition
phospholipids, glycolipids, sterols, and proteins
Term
Most phospholipids and some proteins can
Definition
drift through membrane
Term
Split membranes reveal
Definition
embedded proteins
Term
Hybrid human-mouse cell
Definition
shows some proteins drift within membrane
Term
membrane crossing mechanisms
Definition
diffusion across lipid bilayer, passive transport, active transport, endocytosis, exocytosis
Term
concentration gradient
Definition
means the number of molecules or ions in one region is different than the number in another region
Term
In the absence of other forces, a substance moves
Definition
from a region where it is more concentrated to one where it's less concentrated
Term
Diffusion
Definition
the net movement of like molecules or ions down a concentration gradient
Term
Although molecules collide randomly, the net movement is
Definition
away from the place with the most collisions
Term
factors affecting diffusion rate
Definition
steepness of concentration gradient, molecular size, temperature, electrical or pressure gradients
Term
steepness of concentration gradient
Definition
steeper gradient, faster diffusion
Term
molecular size
Definition
smaller molecules, faster diffusion
Term
temperature
Definition
higher temperature, faster diffusion
Term
Transport proteins
Definition
span the lipid bilayer, interior is able to open to both sides, change shape when they interact with solute
Term
move water-soluble substances across a membrane
Definition
transport proteins
Term
Passive transport
Definition
doesn't require energy inputs, solutes diffuse through a channel inside the protein's interior
Term
Net movement s down concentration gradient
Definition
passive transport
Term
active transport
Definition
require ATP, protein is an ATPase pump, pumps solute against its concentration gradient
Term
how do proteins get to the surface
Definition
vesicle membrane fuses with plasma membrane
Term
endocytosis pathways
Definition
pinocytosis, bulk phase, receptor-mediated, phagocytosis
Term
membrane cycling
Definition
exocytosis and endocytosis continually replace and withdraw patches of plasma membrane
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