Cell Chemistry (I)

Inorganic CompoundsChemical Bonds Solutions and pH

Introduction

• Approach this ppt NOT as lecture notes but as an outline of the basic chemistry that you need to know to understand physiology and ease your way into biochemistry.

• Most of the information can be found in Ch. 1, 2 or 3 of any college Anat. & Physiol. or college Biology textbook.

• This ppt is NOT a substitute for reading the book.

Chemical Bonds

• Review the basic facts about:– Ionic bond– Covalent bond– Polar covalent bond– Hydrogen bond

• The next slides illustrates some of these bonds

Some Bonds Illustrated(Marieb, Fig. 2.9)

Hydrogen Bonds Between Water Molecules(Becker Fig. 2.8)

Solubilization of NaCl(Becker Fig. 2.10)

Water: Significance in Physiology

• Water is essential for life• It is a universal solvent in biological systems

because of its:– Polarity, its cohesiveness, its temperature-stabilizing

capacity and its solvent properties• Water molecules are held by Hydrogen bonds

and these bonds account for its high surface tension, its high boiling point, high specific heat and high heat of vaporization

• Cells are about 75-85% water by weight and one’s body weight is about 60% water.

Terms Linking Solubility of Solutes in Water

• The terms hydrophilic, hydrophobic, amphipathic and oil/water partition coefficient are often used to describe the solubility of a solute in water.

• Hydrophilic solutes are usually polar (they have polar covalent bonds or ionic bonds) and because of their polarity dissolve readily in water

• Hydrophobic solutes are non-polar, therefore, not soluble in water. They are soluble in organic solvents like benzene. They are rich in non-polar covalent bonds.

• Amphipathic solutes have a region that is hydrophilic and another one that is hydrophobic.

Surface Tension Allows Insect to Walk on Water

SOLUTIONS

Know examples of acids, bases & saltsKnow how to calculate, molarity, osmolarity and equivalentsK

Solutions

• Two components: – Solvent– Solute(s)

• In physiology and in all biological systems:– the solvent is H2O– The solutes are many (hundreds) like

• Nutrients like amino acids, glucose• Electrolytes (in physiology = anions & cations)• Gases like O2 and CO2• Wastes like urea, creatinine, uric acid

• Examples of solutions in the body– Plasma– Interstitial fluid– Synovial fluid– Urine

Concentration of Solution• Concentration is a ratio of the amount of solute(s) in a given volume of solvent• Amounts are often expressed in

– Grams (g)– Milligrams (mg)– Mole (m) or millimole (mM)– Milliequivalent (mEq)– Osmole (Osm) or milliosmole (mOsm)

• Volume is often expressed in– Liters (L)– Deciliter(100 mL)– Milliliters (mL)– Microliters

• Examples:– 0.9% NaCl or 135mmole/L NaCl or 135 mEq /L

• GOAL: Given weight in grams, know how to calculate concentrations in molarity, osmolarity and equivalent

Units for Concentration of Solutions

• Percent (%):– 0.9% Sodium chloride (normal saline)– 153 mmole/L Sodium chloride (normal saline)

• ?? Do these have the same amount of NaCl? Justify your answer

• Other units commonly used in physiology– 0.1-0.4 mg/dL creatinine– 70-110 mg/dL glucose– 285-295 mOsm/Kg H2O (For what?– 136-142 mEq/L Sodium

• Units for amount of gas– 80-105 mmHg – Volume %

• Why should I care about these units?– You will constantly run into them in physiology, in reading patients charts and in reading cases.

Inorganic Compounds

• Most of the chemical in your body and the foods that you consume are compounds that are classified as: – Inorganic or– Organic

• Inorganic compounds– Small– Lack carbon atom (some exceptions? )– Most are composed of minerals like K, Ca, P, Mg, Fe– Their atoms are held by ionic bonds

• Characteristic of ionic bonds– They are weak ( easily broken, no enzyme required)

Common Examples of Inorganic CompoundsSignificant in Physiology

• Sodium chloride:– NaCl

• Calcium phosphate– (Ca)3(PO4)2

• Potassium iodide– KI

• Sodium bicarbonate– Na(HCO3)

• Hydrochloric acid– HCl

• Sodium hydroxide– NaOH

• Magnesium hydroxide– Mg(OH)2

• Calcium chloride– CaCl2

Sources of Electrolytes in Physiology

• In physiology, anions and cations are collectively called electrolytes

• Salts– NaCl, KI, Na(HCO3)

• Acids (organic and inorganic)– HCl, H2CO3

– Lactic acid and Acetoacetic acid• Bases

HCO3-

OH-

Ionization of Salts, Acids and Bases

• In H2O the ionic bonds in acids, salts and bases break and the atoms dissociate into ions (or ionize).

• Examples– Replace question marks with correct answer/s

NaCl -> Na+ + Cl-

KI -> ?? H2CO3 --> H+ + HCO3

-

Mg(OH)2 ??

What to Do!

• Look up/review significance of listed ions in physiology or cell biology. – Example: I- (iodide) is essential for thyroxine (T4)

synthesis by the thyroid gland. T4 regulates basal metabolic rate. Now do the same for:

H+

K+

Na+

Cl-

Fe++

Ca++

Questions?

1. HCl2. H2CO3

3. KI (potassium iodide)

4. Na(HCO3)5. Ca3(PO4)2

6. NaCl7. Na(OH)8. Mg(OH)29. H2CO3

• Which one is OR which ones are:– A) acid(s)– B) base(s)– C) salt(s)– D) electrolytes

Inorganic Acids, Bases and Salts

• Acids, bases and salts in the diet are major sources electrolytes (anions and cations) in body fluids.

• In H2O acids, bases and salts ionize or dissociate into anions and cations.

• Examples:– Na:Cl -> Na+ + Cl-

– H:Cl -> H+ + Cl-

– Na:OH -> Na+ + (OH)-

• All ions are not NAKED. They are surrounded by a “shell” of H2O (a hydration shell)

• Hydration shell Illustrated on next slide.

Solubilization of NaCl(Becker Fig. 2.10)

ACIDS, BASES AND PH

Acid: Definition & Examples

• Substances () that ionize (dissociate) into one or more Hydrogen ion (H+) PLUS one or more anion(s)

• H+ is also called a proton.

• Acids are also defined as a proton donors or substances that add proton(s) to a solution.

• Examples of:– Inorganic acids; ---??– Organic acids: ---??

Significance of H+ in Solutions

• H+ concentration in a solution affects the acidity or alkalinity of the solution:pH =log 1/[H+] = -log [H+]

• Note log scale and inverse relationship between [H+] and acidity/alkalinity of a solution

• ? Fill-in blank spaces with the correct term– The higher the [H+] the more ---? the solution– The lower the [H+] the more ---? The solution

pH: Note Log ScaleKnow pH of Some Foods Household Goods

Base: Definition and Examples

• Substance (electrolyte) that ionizes (dissociates) into one or more hydroxide (OH-) ion(s) PLUS one or more cation(s).

• Also defined as substances that accept or bind to or remove free proton(s) from solutions.

• HCO3- (What ion is this?) is a major base in body fluids.

Salt: Definition and Examples

• Substance (electrolyte) dissociate into cations (??) and anions (??) neither of which (??) is H+ or (OH)-

– Examples of salts?

• Products of reaction between an acid and a base

• Example ofsuch a reaction– Na(OH) + HCl -- NaCl + H2O

Body Fluid pH

• Normal body fluid pH is between 7.35 to 7.45.• pH below 7.35 is a condition called acidosis• pH above 7.45 is a condition called alkalosis• Two organs collaborate to maintain normal

body fluid pH:– The lungs and the kidneys

• The lungs do so by regulating the excretion rate of CO2 and the kidneys, by regulating the excretion rate of HCO3

- ions.

Questions

1. Gastric juice (produced by the stomach) has a pH of 5.0 and plasma pH is 7.0. – A) Which one has the lowest H+ concentration: Plasma or gastric

juice?– B) The difference in concentration is how many times lower?

2. Mr. John Doe has a kidney disease that impairs excretion of HCO3

-. – A) Would his plasma HCO3

- Concentration increase, decrease or remain within the normal range?

– B) Is he likely to end up with acidosis, alkalosis or neither? Justify your answer.

3. Would you expect hyperventilation or hypoventilation to impact your body fluid pH? Justify your answer

THE ENDCHEMISTRY I