Slide presentation prepared by

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Guinn/Brewer Essentials of General, Organic, and
Biochemistry
CHAPTER 5 SOLUTIONS, COLLOIDS, AND MEMBRANES
Slide presentation prepared by Martin Brock,
PhD, Eastern Kentucky University
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CHAPTER 5 Solutions, Colloids, and Membranes
DID YOU KNOW?

• 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?

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CHAPTER 5 Solutions, Colloids, and Membranes
DID YOU ANSWER?

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

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CHAPTER 5 Solutions, Colloids, and Membranes
DIALYSIS

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
OUTLINE

• 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

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CHAPTER 5 Solutions, Colloids, and Membranes
MIXTURES

• 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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CHAPTER 5 Solutions, Colloids, and Membranes
5.1 MIXTURES AND SOLUTIONS

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CHAPTER 5 Solutions, Colloids, and Membranes
RECALL

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
COMPOUNDS AND MIXTURES

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
WAYS TO SEPARATE MIXTURES

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
TYPES OF MIXTURES

• 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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CHAPTER 5 Solutions, Colloids, and Membranes
TYPES OF MATTER

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CHAPTER 5 Solutions, Colloids, and Membranes
SOLUTIONS

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
WHAT DISSOLVES?

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
SOLUBILITY

• 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!).

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CHAPTER 5 Solutions, Colloids, and Membranes
SOLUTION STATES

• 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).

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CHAPTER 5 Solutions, Colloids, and Membranes
PRACTICE PROBLEMS

• 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?

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CHAPTER 5 Solutions, Colloids, and Membranes
BIOLOGICAL SOLUTIONS

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

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CHAPTER 5 Solutions, Colloids, and Membranes
WHAT HAPPENS WHEN A COMPOUND DISSOLVES?

• 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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CHAPTER 5 Solutions, Colloids, and Membranes
MOLECULES IN SOLUTION
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CHAPTER 5 Solutions, Colloids, and Membranes
IONIC COMPOUNDS IN SOLUTION

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
NaCl IN AN AQUEOUS SOLUTION

• NaCl in an aqueous solution.

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CHAPTER 5 Solutions, Colloids, and Membranes
ELECTROLYTES

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
FORMULAS OF IONIC COMPOUNDS

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
PRACTICE PROBLEMS

• 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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CHAPTER 5 Solutions, Colloids, and Membranes
5.2 CONCENTRATION OF SOLUTIONS

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CHAPTER 5 Solutions, Colloids, and Membranes
RECALL

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
HOW MUCH IS THERE?

• 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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CHAPTER 5 Solutions, Colloids, and Membranes
SOLUTIONS HAVE A RANGE OF CONCENTRATIONS

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CHAPTER 5 Solutions, Colloids, and Membranes
QUANTIFYING SOLUTIONS

• 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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CHAPTER 5 Solutions, Colloids, and Membranes
COMMON CONCENTRATION UNITS

• Examples of units
• mass/vol
• mass/vol
• Moles/vol
• Equivalents/vol

• Typical examples
• 125 µg/dL (iron in blood)
• 75 mg/dL (glucose in blood)
• 0.9 (saline in i.v. solutions)
• 5 (dextrose in i.v. solutions)
• 100 mmol/L (Cl- in blood)
• 0.018 mol/L (CO2 in blood)
• 19 meq/L (Ca in blood)
• 0.15 eq/L (Na in blood)

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CHAPTER 5 Solutions, Colloids, and Membranes
CALCULATING CONCENTRATIONS

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
AN EXAMPLE

• For a solution containing 137 µg/dL of Fe2, how
  many grams of Fe2 are dissolved per mL of
  solution?
• Recall that there are 100 mL/dL, so

Initial data
Conversion factor
Conversion factor
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CHAPTER 5 Solutions, Colloids, and Membranes
PRACTICE PROBLEMS

• 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 µg are dissolved per L of solution?

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CHAPTER 5 Solutions, Colloids, and Membranes
MASS/VOL SOLUTIONS

• Most i.v. solutions use this form of
  concentration, defined as
• Units must always be g/mL, because waters
  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.

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CHAPTER 5 Solutions, Colloids, and Membranes
RELATED UNITS

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
PRACTICE PROBLEMS

• 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?

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CHAPTER 5 Solutions, Colloids, and Membranes
MOLARITY

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
PRACTICE PROBLEMS

• 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?

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CHAPTER 5 Solutions, Colloids, and Membranes
EQUIVALENTS/LITER

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
IU

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
DRUG DOSAGE CALCULATIONS

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
AN EXAMPLE OF DOSAGE CALCULATIONS

• 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?

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CHAPTER 5 Solutions, Colloids, and Membranes
SOLUTION

• 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

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CHAPTER 5 Solutions, Colloids, and Membranes
FLOW RATES

• 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

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CHAPTER 5 Solutions, Colloids, and Membranes
PRACTICE PROBLEMS

• An order is given to administer 0.25 mg digoxin
  by i.v. over a period of 5 min. The solution
  supplied contains 5 µg 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?

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CHAPTER 5 Solutions, Colloids, and Membranes
CONVERTING CONCENTRATION UNITS

• Often one needs to know concentration in M, but
  the information is given in units of mass/vol.
• Or the reverse might be needed.
• Youll 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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CHAPTER 5 Solutions, Colloids, and Membranes
FLOW CHART FOR CONVERSIONS

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CHAPTER 5 Solutions, Colloids, and Membranes
FOR EXAMPLE

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
PROBLEM CONTINUED

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

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CHAPTER 5 Solutions, Colloids, and Membranes
PRACTICE PROBLEMS

• 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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CHAPTER 5 Solutions, Colloids, and Membranes
5.3 COLLOIDS AND SUSPENSIONS

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CHAPTER 5 Solutions, Colloids, and Membranes
TYPES OF MIXTURES

Mixtures
Heterogeneous
Homogeneous
Suspensions
Solutions
Colloids
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CHAPTER 5 Solutions, Colloids, and Membranes
COLLOIDS

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
SUSPENSIONS

• 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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CHAPTER 5 Solutions, Colloids, and Membranes
COMPARING COLLOIDS AND SUSPENSIONS
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CHAPTER 5 Solutions, Colloids, and Membranes
EXAMPLES

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CHAPTER 5 Solutions, Colloids, and Membranes
BLOOD HAS PROPERTIES OF ALL THREE TYPES OF
MIXTURES

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CHAPTER 5 Solutions, Colloids, and Membranes
PRACTICE PROBLEMS

• 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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CHAPTER 5 Solutions, Colloids, and Membranes
5.4 PROCESSES THAT MAINTAIN BIOCHEMICAL BALANCE
IN YOUR BODY

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CHAPTER 5 Solutions, Colloids, and Membranes
SEMIPERMEABLE MEMBRANES

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
SIMPLE DIFFUSION

• Molecules may cross a membrane through simple
  diffusion.

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CHAPTER 5 Solutions, Colloids, and Membranes
CELL MEMBRANES

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
OSMOSIS AND DIALYSIS

• 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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CHAPTER 5 Solutions, Colloids, and Membranes
OSMOSIS AND DIALYSIS

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CHAPTER 5 Solutions, Colloids, and Membranes
OSMOSIS

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
DIRECTION OF DIFFUSION

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
OSMOSIS

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

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CHAPTER 5 Solutions, Colloids, and Membranes
OSMOTIC PRESSURE

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
REVERSE OSMOSIS

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

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CHAPTER 5 Solutions, Colloids, and Membranes
OSMOSIS IN RED BLOOD CELLS (RBCs)

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
PRACTICE PROBLEMS

• 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?

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CHAPTER 5 Solutions, Colloids, and Membranes
DIALYSIS

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
PRACTICE PROBLEM

• 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

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CHAPTER 5 Solutions, Colloids, and Membranes
SUMMARY OF MAIN CHAPTER POINTS, P1

• 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.

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CHAPTER 5 Solutions, Colloids, and Membranes
SUMMARY OF MAIN CHAPTER POINTS, P2

• 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.