Download Diffusion _ Cell Transport Powerpoint

DIFFUSION & CELL TRANSPORT
MRS. PAEZ
ANATOMY & PHYSIOLOGY
DIFFUSION
• DEFINITION: THE NET MOVEMENT OF
MOLECULES FROM AN AREA OF RELATIVELY
HIGH CONCENTRATION TO AN AREA OF
RELATIVELY LOW CONCENTRATION.
• THE DIFFERENCE BETWEEN HIGH AND LOW
CONCENTRATIONS IS THE CONCENTRATION
GRADIENT.
• DIFFUSION PROCEEDS “ DOWN THE
CONCENTRATION GRADIENT” OR
“DOWNHILL”
• A PASSIVE PROCESS: DOES NOT REQUIRE THE
CELL TO EXPEND ENERGY
DIFFUSION IN THE BODY
INTRACELLULAR CONCENTRATION OF
CARBON DIOXIDE IS HIGH, BECAUSE IT IS
GENERATED INSIDE THE CELL BY RESPIRATION.
THE CONCENTRATION OF CO2 IS MUCH
LOWER OUTSIDE THE CELL.
THE CELL MEMBRANE IS FREELY PERMEABLE
TO CO2 AND THEREFORE IT DIFFUSES INTO
THE EXTRACELLULAR FLUID- DOWN ITS
CONCENTRATION GRADIENT-AND THEN
INTO BLOODSTREAM.
DIFFUSION ACROSS THE CELL MEMBRANE
• SUBSTANCES DIFFUSE:
1) EITHER THROUGH THE PHOSPHOLIPID PORTION :
ALCOHOL, FATTY ACIDS, STEROIDS, OXYGEN,
CARBON DIOXIDE.
2) OR THROUGH PROTEINS IN THE MEMBRANE: WATER
& IONS ( SODIUM, POTASSIUM, CALCIUM)
OSMOSIS
• OSMOSIS: DIFFUSION OF WATER ACROSS A MEMBRANE
• SOLUTES: DISSOLVED MATERIALS
• WATER WILL FLOW ACROSS A MEMBRANE TOWARD THE
SOLUTION CONTAINING THE HIGHER SOLUTE
CONCENTRATION ( BECAUSE THAT’S WHERE THE
CONCENTRATION OF WATER IS LOWER )
• AS OSMOSIS OCCURS, WATER MOLECULES CROSS THE
MEMBRANE UNTIL THE SOLUTE CONCENTRATIONS IN THE
TWO SOLUTIONS ARE IDENTICAL.
HYPOTONIC SOLUTION
• SOLUTION THAT CONTAINS
LESS SOLUTE THAN THE CELL.
WATER WILL FLOW INTO
THE CELL CAUSING IT TO
SWELL.
• IN RED BLOOD CELLS (
RBC’S) THIS CAUSES THE
CELL TO BURST- CALLED
HEMOLYSIS
ISOTONIC SOLUTION
A SOLUTION THAT CONTAINS AN EQUAL
AMOUNT OF SOLUTE AS THE CELL.
EQUILIBRIUM EXISTS BECAUSE FOR EVERY
WATER MOLECULE THAT MOVES OUT OF
THE CELL, ANOTHER MOVES IN TO REPLACE
IT.
SALINE IS GIVEN TO PATIENTS BECAUSE IT
IS ISOTONIC TO THE EXTRACELLULAR
FLUIDS OF THE BODY.
HYPERTONIC SOLUTION
•A SOLUTION THAT CONTAINS
MORE SOLUTE THAN THE CELL.
WATER WILL FLOW OUT THE CELL
CAUSING IT TO SHRIVEL AND
DEHYDRATE.
•IN RED BLOOD CELLS ( RBC’S) THIS
CAUSES THE CELL TO SHRIVEL AND
SHRINK- CALLED CRENATION.
FILTRATION
KIDNEYS
• WHERE OSMOTIC PRESSURE
FORCES WATER ACROSS A
MEMBRANE. IF SOLUTE
MOLECULES ARE SMALL
ENOUGH TO FIT THROUGH
MEMBRANE PORES, THEY WILL BE
CARRIED ALONG
• OCCURS ALONG THE WALLS OF
SMALL BLOOD VESSELSPUSHING WATER AND
DISSOLVED NUTRIENTS INTO
TISSUES.
CARRIER- MEDIATED TRANSPORT
•DEFINITION: MEMBRANE PROTEINS BIND SPECIFIC IONS
OR ORGANIC SUBSTRATES AND CARRY THEM ACROSS THE
CELL MEMBRANE
•THESE PROTEINS ARE SUBSTRATE-SPECIFIC-THEY ONLY BIND
TO SPECIFIC MOLECULES
•PASSIVE OR ACTIVE PROCESS
• A PASSIVE PROCESS
FACILITATED DIFFUSION
• DEFINITION: A TYPE OF CARRIER-MEDIATED
TRANSPORT WHERE COMPOUNDS ARE
TRANSPORTED ACROSS THE MEMBRANE BY
CARRIER PROTEINS
• THE SUBSTANCE BINDS TO A RECEPTOR SITE ON
THE CARRIER PROTEIN, CAUSING THE SHAPE OF
THE PROTEIN TO CHANGE. THIS MOVES THE
MOLECULE TO THE INSIDE OF THE CELL.
• RATE OF DIFFUSION IS LIMITED BY AVAILABILITY
OF CARRIER PROTEINS IN MEMBRANE.
ACTIVE TRANSPORT
• MOLECULES MOVED “UPHILL” OR
AGAINST THE CONCENTRATION
GRADRIENT ( FROM LOW TO HIGH
CONCENTRATION)
• ATP IS REQUIRED
• EXAMPLE: ION PUMPS- MOVE
SPECIFIC IONS IN OR OUT OF THE
CELL
ION EXCHANGE PUMPS
• SODIUM-POTASSIUM PUMP
• MAINTAINS THE LEVEL OF NA+ HIGH IN
EXTRACELLULAR FLUIDS
• KEEPS LEVEL OF K+ HIGH IN THE
INTERIOR OF THE CELL ( CYTOPLASM)
• MAINTAINS HOMEOSTASIS OF CELLSUSES 40% OF ATP PRODUCED BY CELLS