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Lecture 7

BIOL 102 Lecture Notes - Lecture 7: Hydrophile, Conformational Change, Active Transport


Department
Biology
Course Code
BIOL 102
Professor
Wayne Snedden
Lecture
7

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Fluidity of Membranes
Phospholipids in plasma membrane can move within bilayer
Most lipids and some proteins drift laterally
Lateral movement occurs 10^7 times per second
§
Rarely does a molecule flip-flop transversely
Factors affecting fluidity
Length of fatty acyl tails
Presence of double bonds in the acyl tails
Presence of cholesterol (animals)
Diffusion
Diffusion is the net passive movement of particles from a region in which
they are in higher concentration to regions of lower concentration
Facilitated Diffusion
Carrier proteins undergo a subtle change in shape that translocates the
solute-binding site across the membrane
Osmosis
Water diffuses through a membrane to balance solute concentration
Osmotic pressure can result if solutes are impermeable (cell shrinking,
swelling)
Water will always move passively down its gradient- toward higher solute
concentration
Tonicity
Tonicity is the ability of surrounding solution to cause cells to gain or lose
water (swell or shrink)
Loss of turgor can result in wilting, and eventually plasmolysis and death
Transport Proteins
Transports proteins enable biological membranes to be selectively
permeable
Two main classes:
Channels
Conduit for the direct diffusion of ions or molecules across
the membrane
When a channel is open, a solute directly diffuses through the
channel to reach he other side of the membrane
1.
Chapter 7
Wednesday, October 3, 2018
9:33 AM
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