Slide presentation prepared by Martin Brock, PhD, Eastern Kentucky University

2. What classes of compounds are removed by dialysis in the kidneys? What is the principal material removed in the kidneys? What type of mixture is urine?

3. The kidneys produce urine, a solution containing water as the solvent and a number of unwanted small molecules and ions as solutes.

4. In dialysis, small molecules and ions can flow from a solution of higher concentration to a lower concentration solution. In this chapter, mixtures such as solutions will be discussed and you will learn how to use and calculate solution concentrations.

5. 5.1 Mixtures and Solutions 5.2 Concentration of Solutions 5.3 Colloids and Suspensions 5.4 Processes that Maintain Biochemical Balance in Your Body

6. A mixture contains two or more elements or compounds in any proportion. This is different from a compound in which elements are present in exact or definite proportions. Biological systems are composed of many mixtures with many components. Chemistry determines the make-up of mixtures: Which substances are present How much of each is present

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8. Pure substances may be either elements or compounds. Some compounds are ionic, others are covalent. Ionic compounds form a crystal lattice. When ions dissolve, the solution contains electrolytes. Molecular structure allows us to predict polarity. Interactions among molecules may include hydrogen bonds and dipole-dipole interactions.

9. Composition of mixtures may vary. Composition of compounds are definite. Mixtures may be separated using physical means. Compounds must be separated into component elements using chemical procedures only.

10. Take advantage of differences in physical properties. Solubility differences: sugar and sand, for example Magnetic differences: iron filings and dirt Boiling point differences: Distilling whiskey Other differences are exploited by analytical instrumentation, for example, drug tests on athletes, medical tests on blood samples, water quality testing, and many others.

11. Heterogeneous mixtures have an uneven distribution of components. For example, a chocolate chip cookie Homogeneous mixtures have an even distribution of components. Solutions are homogeneous mixtures. For example, a cup of coffee is the same throughout. Classifications of matter are on the next slide.

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13. Solutions are homogeneous mixtures. They may be solids, liquids, or gases. Composed of two parts: Solvent, the major component Solutes, minor components The main solvent in biological systems is water.

14. Like-dissolves-like rule: In general, polar solvents (like water) dissolve polar solutes (like sugar). Non-polar solvents (like fish oil) can dissolve non-polar solutes (like vitamin E). Polar solvents will not dissolve non-polar solutes (so oil and vinegar will not mix). Solutions containing water as the solvent are aqueous solutions.

15. If two liquids do not mix, they are immiscible (such as oil and water), and if they mix in any proportion (such as alcohol and water), they are miscible. Most solutes have a maximum limit of solubility in which no more can dissolve. Such solutions are saturated. Additional solute will not dissolve, and forms a separate phase, often as a precipitate. Examples include kidney stones (ouch!).

16. A solution may be a solid, liquid, or a gas. Solid solutions may include alloys such as brass and dental amalgams. A liquid solution may be a rum-and-coke, containing: Solids (sugar) Liquids (alcohol) Gases (CO2) Air is a gas solution, containing dissolved gases such as oxygen and nitrogen, water (a liquid), and odors (which may be solids).

17. 1. Identify the solute and solvent in each solution: 5 mL of ethanol and 25 mL water 200 g of water containing 6 g of NaCl 0.005 L of CO2 and 2 L O2 2. What does the phrase �like dissolves like� mean? 3. What is a saturated solution? How can you tell when a solution is saturated?

18. Most common solutes in biological solutions are: Molecules Sugars, proteins, nucleic acids, vitamins Ions Na+, K+, HCO3-, Cl-, HPO42-, Ca2+, Zn2+ Gases O2, CO2

19. If it is composed of molecules, the covalent bonds remain intact. The molecules uniformly disperse throughout the solution. In aqueous solutions, each solute molecule interacts with many water molecules by way of weak dipole-dipole and hydrogen bond forces.

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21. When ionic compounds dissolve, the crystal lattice breaks apart into individual ions. Each ion is surrounded by solvent molecules. For example, in salt water: Each Na+ ion is attracted to the partially negative O atoms on water molecules. Each Cl- ion is attracted to the partially positive H atoms on water molecules. Each ion is surrounded by many water molecules.

22. NaCl in an aqueous solution.

23. Electrolytes are dissolved ionic compounds. These solutions conduct electricity due to electrolyte charge. Roles of electrolytes in our body include regulating Nerve action Muscle action Cell volume Water flow Imbalances of electrolytes cause serious difficulties.

24. The formula unit of an ionic compound tells how many of each ion will form in solution. For example, NaCl Na+ + Cl- Every unit dissolving results in one of each ion. MgCl2 Mg2+ + 2Cl- The number of ions present in solution follows the same ratio as present in the formula unit.

25. Describe the formation of an aqueous solution of glucose, C6H12O6 from pure glucose. For the following compounds, how many ions of each type will be produced per formula unit in aqueous solution? MgCl2 K3PO4 NaHCO3

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27. Substances may be measured either in mass units or in molar units. A mole is a unit of measurement consisting of a specific number of objects. Many measurements include the metric prefixes.

28. A solution may have a lot of solute present. Such a solution is concentrated. A solution may have very little solute. These solutions are dilute. One central aim in chemistry, especially in medical science, is to determine how much solute, its concentration, is present per unit of volume.

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30. Concentration = Note that the amount of the solution is the sum of solvent plus solute. Types of concentration analysis: Concentration based on mass (e.g., g/L, or mg/L) Concentration based on moles (e.g., mol/L, or mmol/L)

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32. Concentrations are always a division of one unit (mass or moles) by another (volume). Ratios mean conversion factors may be used: Mass/vol or vol/mass may be used to convert from one type of concentration to another. Metric prefixes, when present, must be noted in calculations.

33. For a solution containing 137 �g/dL of Fe2+, how many grams of Fe2+ are dissolved per mL of solution? Recall that there are 100 mL/dL, so

34. 1. Isuprel, used to treat asthma, comes in i.v. form at a concentration of 4 mg in 500 mL. What is the concentration of this solution in g/L? 2. For a solution containing 99 mg/dL glucose, how many �g are dissolved per L of solution?

35. Most i.v. solutions use this form of concentration, defined as: Units must always be g/mL, because water�s density is 1.00 g/mL; every mL of water weighs 1.00 g. I.v. saline is 0.9 % NaCl, so every 100 mL of saline solution contains 0.9 g of NaCl.

36. The terms ppm and ppb are analogous to %. Parts per million is defined as follows: Parts per billion is similar: Note that % is really the same as parts per hundred.

37. 1. Calculate the % m/v of sucrose in a carbonated beverage that contains 28 g of sucrose in 315 mL of beverage. 2. You have been asked to prepare one L of a 0.45 % NaCl (% m/v) solution for i.v. therapy. How many g of NaCl should you weigh out?

38. This is defined as moles per liter and is abbreviated M: This is a measure of how many molecules are present in a solution. A 1 M solution of anything contains 1 mole of solute in each liter; a 1 mM solution has 1/1000 this much.

39. 1. How many moles of potassium ions (K+) are there in 5.0 L of 2.5 mM K3PO4? 2. A solution having a volume of 3.0 L contains 23 mmol of O2 (oxygen). What is the concentration of oxygen in this solution in mol/L?

40. Equivalents (eq) are related to moles. These units are applied to electrolytes. Moles of ion x the charge on each ion = equivalents Corresponds to the molarity of charge. 1 eq/L is the same as 1 mol/L if the charge is + or � 1. For ions with 2+ or 2- charge, eq are double the mol. So 1 M Ca2+ or S2- is 2 eq/L. So 1 M Fe3+ or PO43- is 3 eq/L. Ions in biological fluids are usually given in meq/mol.

41. International units (IU) often used to specify concentration of biologically active solutes. The amount of material in an IU varies with the type of solute, depending on how active the material is.

42. This is one of the most important calculations commonly made in health care fields. It is no different than any conversions between different units of measurements.

43. An order is given for 500 mg of amoxicillin to be administered to a patient every six hours. For an oral suspension of amoxicillin that contains 250 mg of amoxicillin in every 5 mL, how many mL of the suspension should you administer to the patient every six hours?

44. Express problem as conversion factors. The supplied unit is 500 mg of drug. The requested unit is mL of suspension. You are given the concentration of the drug as m/v: 250 mg amoxicillin per 5 mL of suspension. So use Set up calculation so supplied units cancel 10 mL every six hours

45. Drugs are often administered at a specific dosage per unit of time, called the flow rate. For example: An order is given to infuse 500 units per hour of Heparin, an anticoagulant. The IV bag supplied contains 25,000 units in 250 mL. At what flow rate in mL per hour should the solution be infused into the patient? For this, use two conversion factors: Multiply so units cancel:

46. An order is given to administer 0.25 mg digoxin by i.v. over a period of 5 min. The solution supplied contains 5 �g digoxin in 2 mL. What should the flow rate be in mL/min? A patient on diuretics is prescribed 30 meq of potassium (K+) every day. The solution supplied contains 40 meq of KCl in every 15 mL. How many mL of this solution should you give to the patient every day?

47. Often one needs to know concentration in M, but the information is given in units of mass/vol. Or the reverse might be needed. You�ll need to be able to convert between these types. It helps to set up a flow chart outlining the steps. Each step uses conversions just like those you have been doing.

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49. What is the molarity of Na+ in the 0.9% saline in an i.v. drip bag? Convert percentages to moles: Convert between moles NaCl and moles Na+. Check subscripts in formula; in this case each NaCl produces one Na+.

50. So: Convert to liters: So the final answer is that 0.9% NaCl has 0.15 mol/L Na+, or better, 0.15M Na+.

51. What is the % (m/v) sucrose in a 25 mM sucrose solution? The molar mass of sucrose is 342.3 g/mol What is the % (m/v) MgI2 in a 0.35 eq/L Mg2+ solution, assuming that the only source of Mg2+ is the MgI2?

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54. Homogeneous mixtures that are not solutions Composed of much larger particles than would be found in a solution May be composed of large molecules, or aggregates of many molecules The major component of a colloid is called the medium.

55. A suspension is a heterogeneous mixture. It will eventually settle out. Particles are very large. Major component is the dispersion medium. Particles are either solids or liquids.

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59. Describe the differences between a solution, a colloid, and a suspension. Explain why humid air is considered a solution, while mist, which is also a mixture of water in air, is considered a colloid.

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61. A membrane is a barrier between two environments. A semipermeable membrane allows certain molecules to cross. All cells and organelles within cells are surrounded by semipermeable membranes.

62. Molecules may cross a membrane through simple diffusion.

63. These surround all cells and maintain different concentrations of ions and molecules inside and outside the cells. Ions and large molecules require special transport systems to carry them across the membrane as needed.

64. These are two ways by which molecules may cross semipermeable membranes. In osmosis, water may cross the membrane, but not other substances. In dialysis, water or small solutes such as ions or sugars may cross the membrane, but not large molecules such as proteins. In all cases, molecules move through simple diffusion from low concentration to higher concentration.

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66. In osmosis, solvent (water) moves across a membrane so as to equalize solute concentration across membrane. Flow of water is determined by total number of moles of all solutes on both sides of membrane. Laxatives work by increasing the number of moles of solute outside cells, drawing out water into the stool.

67. In osmosis, water always moves from low solute concentration to high solute concentration. Three types of solutions:� Hypertonic � solution with a higher solute concentration than inside cells. Hypotonic � solution with the lower solute concentration compared with cells. Isotonic � solutions have equal solute concentrations to cell contents.

68. In osmosis, water flows in order to dilute solutions until concentrations are equal.

69. Osmotic flow can be reversed if pressure added to hypertonic side. Water then flows from high concentration solute to low concentration solute. This can be used to purify sea water or other impure water sources. The amount of pressure needed to overcome natural osmosis is called the osmotic pressure.

70. When excess pressure is applied to impure water, the backwards flow is called reverse osmosis. This can be used to purify water.

71. If RBCs are immersed in hypotonic or hypertonic solutions, water will cross the RBC membrane inappropriately, destroying its function. Eventually the cells in hypotonic solution will burst in what is called hemolysis; the cells in hypertonic solution shrivel during crenation.

72. You have probably heard that if you are stranded on a desert island, it is not wise to drink large quantities of sea water in place of fresh water. Why is this true? What might happen if an IV bag were filled with distilled water instead of isotonic saline?

73. In dialysis, small solutes can cross a special membrane. They always cross from high to low concentration. Dialysis is used to separate solute molecules from colloidal particles. Kidneys carry out dialysis by removing urea and creatinine and retaining water and electrolytes Artificial dialysis can be used if kidneys are diseased.

74. Consider two solutions that are separated by a semipermeable membrane that is designed for dialysis. One solution is pure water; the other is a solution [0.9% (m/v) NaCl] of red blood cells. Based on the principles of dialysis, which would you expect to take place? hemolysis crenation neither

75. Mixtures and Solutions Mixtures contain components in any proportion. They can be separated into components. Solutions contain solvent (major) and solute (minor). Like dissolves like rule explains solubility. In dissolving a molecule, bonds remain intact. In dissolving an ionic compound, ions separate and are surrounded by water. Concentration of Solution Expressed as the ratio of mass or moles per unit volume. Typical units also include % mass/vol and eq/vol.

76. Colloids and Suspensions Colloids are homogeneous with large solute molecules. Suspensions are heterogeneous and will settle out. Processes that Maintain Biochemical Balance in Your Body Molecules may cross semipermeable membranes such as found surrounding cells. Water crosses membranes in osmosis to equalize concentrations. Small solutes may cross membranes in dialysis. Molecules cross membranes in direction of decreasing concentration. Relative concentrations across membranes may be hypertonic (higher), hypotonic (lower), and isotonic (the same). Colloidal particles do not cross semipermeable membranes.