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: 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 OSMOSIS: DIFFUSION OF WATER ACROSS A MEMBRANE SOLUTES: DISSOLVED MATERIALS 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 ) 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. 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. 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 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 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. 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 A PASSIVE PROCESS DEFINITION: A TYPE OF CARRIER-MEDIATED TRANSPORT WHERE COMPOUNDS ARE TRANSPORTED ACROSS THE MEMBRANE BY CARRIER PROTEINS 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. 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. 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) MOLECULES MOVED “UPHILL” OR AGAINST THE CONCENTRATION GRADRIENT ( FROM LOW TO HIGH CONCENTRATION) ATP IS REQUIRED ATP IS REQUIRED EXAMPLE: ION PUMPS- MOVE SPECIFIC IONS IN OR OUT OF THE CELL EXAMPLE: ION PUMPS- MOVE SPECIFIC IONS IN OR OUT OF THE CELL

ION EXCHANGE PUMPS SODIUM-POTASSIUM PUMP SODIUM-POTASSIUM PUMP MAINTAINS THE LEVEL OF NA + HIGH IN EXTRACELLULAR FLUIDS MAINTAINS THE LEVEL OF NA + HIGH IN EXTRACELLULAR FLUIDS KEEPS LEVEL OF K + HIGH IN THE INTERIOR OF THE CELL ( CYTOPLASM) KEEPS LEVEL OF K + HIGH IN THE INTERIOR OF THE CELL ( CYTOPLASM) MAINTAINS HOMEOSTASIS OF CELLS- USES 40% OF ATP PRODUCED BY CELLS MAINTAINS HOMEOSTASIS OF CELLS- USES 40% OF ATP PRODUCED BY CELLS