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Lecture 4

NATS 1675 Lecture Notes - Lecture 4: Robert Crippen, Lipid Bilayer, Cell Membrane

by

Department
Natural Science
Course Code
NATS 1675
Professor
Robert Crippen
Lecture
4

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NATS 1675 – LECTURE# 4– Notes continued from January 11 th
2016
Professor: Robert Crippen
Simple Diffusion:
This is the random movement of molecules from an area of higher concentration to an
area of lower concentration until the equilibrium is achieved
Therefore, a concentration gradient is required for this to occur, once equilibrium is
achieved, the molecules continue to move across the membrane, but there is no net
change in concentration
Examples of substances that move through the membrane in this manner include lipid
soluble substances such as alcohol; gases such as O2 and CO2 can diffuse directly
through the phospholipid bilayer; and water molecules, other small molecules and some
ions can pass through pores formed by integral proteins
Concentration gradient: it is high on one side and low on the other side
Osmosis:
It is the diffusion of water across the plasma membrane when non-diffusible solutes are
more concentrated on one side of the membrane than the other
The net movement of water is in the direction of the non-diffusible solutes until the
osmotic balance is restored
Solution: it is a mixture of a solvent and a solute ex. Professor Crippen likes his coffee
black however he decides to add sugar which becomes a solute
Solvent: What is doing the dissolving
Solute: What is being dissolved
Facilitated Transport:
This is a type of diffusion that requires a carrier substance (a protein molecule)
Like simple diffusion, it only functions with a concentration gradient and requires no
energy
Ex. Sugar molecules and amino acids
Simple Diffusion Facilitated Transport
Things are dissolving right through the
phospholipid bilayer moving right through the
pore
It is a revolving door – the protein molecule is
the carrier that is required by protein
Active Transport:
The method is similar to facilitated transport in that a carrier substance is required
however the substances can be moved against a concentration gradient & energy is
required (ATP)
Examples: NA+ (sodium), K+ (potassium), CA++ (calcium), FE+ (iron), H+ (Hydrogen), I-
(iodine)
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