Transcript Diffusion and Active Transport

DIFFUSION AND ACTIVE TRANSPORT
By Sir William Harrison Hawk Esquire, PhD
WHAT IS DIFFUSION?

Diffusion is the movement molecules from an
area of high concentration to an area of low
concentration.
Actually,
that would
be diffusion
MORE ON DIFFUSION:
In biology, it refers to the movement of gas and
liquid particles at temperatures above absolute
zero.
 Diffusive equilibrium- when the concentrations
of diffusing substances in the two
compartments becomes equal
 Diffusion is passive

Abiotic Factors Affecting Diffusion
Temperature
 Viscosity (density)
 Mass of particles

Facilitated Diffusion



Large and polar molecules cant get across the
membrane by simple diffusion (glucose, lipids, amino
acids, etc.)
they are transported across the membrane by
channel proteins and carrier proteins
Still passive, ALWAYS goes with concentration gradient
Osmosis
Osmosis is the diffusion of water across a semipermeable membrane.
 Water moves from an area of low solute
concentration to high solute concentration
 Aquaporin is an integral protein that speeds up
movement of water molcules

Osmotic Control
Osmosis is vital is maintaining homeostasis
 Goal is to be isotonic

Primary Active Transport
Requires ATP
 Uses Integral protein pumps to move ions and
large molecules across the cell membrane
 Molecules can go with OR against the
concentration gradient

Secondary Active Transport
Energy does not come directly from ATP
 Instead it comes from the concentration
gradient/ movement of sodium ions in primary
active transport

http://www.youtube.com/watch?v=JGF6ry0SWPs