diffusion & cell transport mrs. paez anatomy & physiology
TRANSCRIPT
DIFFUSION & CELL TRANSPORT
MRS. PAEZ
ANATOMY & PHYSIOLOGY
DIFFUSION Click icon to add picture• 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 Click icon to add picture
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 Click icon to add pictureA 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 Click icon to add picture
•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 VESSELS-PUSHING 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
FACILITATED DIFFUSION
• A PASSIVE PROCESS
• 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 CELLS- USES 40% OF ATP PRODUCED BY CELLS