Al-Hujraat Surah: 49 Aya: 11

REQUIREMENTS FOR LIVING All living things have certain requirements , which they must satisfy in order to remain alive; Maintain homeostasis These include exchanging gases (O2 and CO2), Taking in water, minerals, Vitamins and food, Eliminating wastes. These tasks happen at the cellular level. Molecules move through the cell membrane by Osmosis and inside the cell by diffusion.

OSMOSIS and DIFFUSION

Introduction Since the early days of civilization mankind have adopted simple forms of membranes. In early agriculture communities, household sieves were invented and developed to separate fine grain from coarse grain particles and shells. Similarly, cheese cloth was made from cotton fibers and used to manufacture cheese.

Introduction All forms of separation are based on differences in particle size. However, developments in membrane technology have focused on adoption of other separation mechanisms, such as differences in solution and diffusion rates of various species across the membrane material.

Membrane based Separation A number of membrane-based desalination processes are used on industrial scale. the membrane-based processes include Reverse osmosis, Nanofiltration, Ultrafiltration, and Microfiltration.

Differences among membranes Microfiltration operates on a particle size range of 0.10 µm to 0.15 µm. Ultrafiltration operates on a particle size range of 0.15 µm to 5xl0-2 µm Nanofiltration operates on a particle size range of 5xl0-2 µm to 5x10-3 µm Reverse osmosis operates on a particle size range of 5xl0-3 µm to 10-4 µm.

Molecules are always moving Molecules move randomly and bump into each other and other barriers

Concentration gradient Concentration Gradient - change in the concentration of a substance from one area to another.

Diffusion Molecules in solution tend to slowly spread apart over time. This is diffusion.

Diffusion Movement of molecules from an area of high concentration to an area of lower concentration. Factors that affect the rate of diffusion: size of molecules, size of inter molecular space , temperature, pressure, and concentration.

Diffusion [High] [Low] diffuse, low energy molecules concentrated, high energy molecules [High] [Low] diffuse, low energy molecules

Diffusion will continue until equilibrium is reached Diffusion will continue until equilibrium is reached. This means there will be an equal distribution of molecules throughout the space. This is why food coloring moves throughout a beaker of water; why odors smell strong at first and then disappear over time. Equilibrium, a result of diffusion, shows the uniform distribution of molecules of different substances over time as indicated in the above diagram.

How is this Important ? Diffusion is an important concept for humans because our very existence depends on it. The cells of the human body utilize diffusion every day! Can you think of where in the human body diffusion might be important? An important place in the human body where diffusion occurs is the lungs. Oxygen diffuses from inside the lungs to the circulatory system.

OSMOSIS Osmosis is the flow of solvent through a semi- permeable membrane such as cell membrane, from a dilute solution to concentrated solution. Osmosis is a selective process.

Osmosis Osmosis is the movement of WATER across a semi-permeable membrane At first the concentration of solute is very high on the left. But over time, the water moves across the semi-permeable membrane and dilutes the particles.

Osmosis Osmosis is a special case of diffusion commonly found in biological systems (In your cells). Water transport and turgor pressure in the cell is maintained by osmosis.

Turgor Pressure Turgor: pressure against the cell membrane Hypotonic: there is an excess of water and the cell bursts. Hypertonic: there is not enough water and the cells shrivels. Osmosis regulates these occurrences.

Osmosis Eventually the pressure difference between the arms stops osmosis.

Force per unit area that prevents water from passing through membrane Osmotic Pressure Force per unit area that prevents water from passing through membrane

Osmotic Pressure The hydrostatic pressure at equilibrium which prevents the passage of more solvent through the semi permeable membrane is called osmotic pressure.

P If applied pressure is too low, H2O flows into the region of higher solute concentration... “Down the concentration gradient” for H2O. P Membrane Pure H2O H2O + Solutes

P If applied pressure is too high, H2O flows into the region of lower solute concentration... Against the natural concentration gradient for H2O. --Reverse Osmosis P Membrane Pure H2O H2O + Solutes

P Minimum pressure required to maintain equal flow rates (to prevent infusion of H2O). Proportional to solute concentration differences across membrane. P Membrane Pure H2O H2O + Solutes

Units of Osmotic Pressure OSMOLE Non electrolyte: 1 M Solution = 1 osmole = 22.4 atmospheres = 22.4 x 760 mm Hg = 17024 mm Hg. Electrolyte: Dissociates into ions Bimolecular double osmotic pressure….NaCl Tri molecular tripple osmotic pressure…..CaCl2

Osmotic Pressure Osmotic pressure, , is the pressure required to stop osmosis: Π = osmotic pressure M = Molarity (mol/L) R = Ideal Gas Constant T = Temperature (K)

Problem #2 Calculate osmotic pressure for 0.10 M Na3PO4 at 20°C. Na3PO4 ionizes into 4 particles, (3 Na + 1 PO4), Ion conc. is = 0.40 M p = MRT = (0.40) (0.0821) (293) = 9.6 atm

Problem #1: Calculate molarity if soln. in water (300K) has osm Problem #1: Calculate molarity if soln. in water (300K) has osm. pressure of 3.00 atm M = p / RT (3.00 atm) [0.0821 atm.L / mol) (300K)] = 0.122M

Osmosis – A Special kind of Diffusion Diffusion of water across a selectively permeable membrane (a barrier that allows some substances to pass but not others). The cell membrane is such a barrier. Small molecules pass through – ex: water Large molecules can’t pass through – ex: proteins and complex carbohydrates

Hypotonic – The solution on one side of a membrane where the solute concentration is less than on the other side. Hypotonic Solutions contain a low concentration of solute relative to another solution. Hypertonic – The solution on one side of a membrane where the solute concentration is greater than on the other side. Hypertonic Solutions contain a high concentration of solute relative to another solution.

Over time molecules will move across the membrane until the concentration of solutes is equal on both sides. This type of solution is called ISOTONIC.

Cytoplasm is a solution of water and solids (solutes dissolved in the water). Water moves into and out of cells because of the different concentrations of the solutes. Different kinds of cells react differently depending on the solution they are in. Below are examples of red blood cells in different types of solutions and shows what happened to the red blood cells.

PLANT CELLS Hypotonic Solution Hypertonic Solution Turgor Pressure builds in the cell and causes osmosis to stop because of the rigid cell wall. Plants will wilt when cells lose water through osmosis.

PASSIVE TRANSPORT Passive transport occurs without expenditure of energy. Molecules move using their own kinetic energy . Diffusion and osmosis are examples of passive transport. Passive transport allows cells to get water, oxygen and other small molecules that they need. It also allows the cell to get rid of waste such as carbon dioxide. DIFFUSION OSMOSIS

Reverse Osmosis Water Purification

Home water purification by reverse osmosis

Kidney and Dialysis

Artificial kidney

A Dialysis Unit

Principle of Dialysis

Transmembrane Diffusion Arterial End “Head pressure” --High Venous End “Head pressure” --Low Tissue Cell Wastes Head pressure of heart “pushes” nutrients and water into cell (PBLOOD> POSMOTIC). Nutrients Hypertonic blood “draws” wastes into blood (POSMOTIC>PBLOOD) .

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