ME01 - Water and pH Flashcards
TBW of Adults
50-60% of total body weight
TBW of Children
75% of total body weight
Intracellular percent in TBW
60%
Extracellular percent in TBW
40%
Shape of Water
Tetrahedron
O-H bond distance
0.958A
Angle formed by the three atoms
105 degrees
Water as a dipole
Electrical charge distributed asymmetrically
Ability of a material to resist formation of an electric field
Dielectric constant
Water has HIGH DIELECTRIC constant. TRUE OR FALSE?
TRUE. It has high dielectric constant thus it can decease the force of attraction between charged particles. This enables water to dissolve salts
What is the dielectric constant of water?
Water - 78.5
Water as an excellent nucleophile
Nucleophile is an electron-rich molecule that attacks an electron-poor atom called an elecrophile
Force of attraction between two oppositely charged ions
Ionic Bonding
Example of Ionic Bonding
Na-Cl
Bonding between molecules within metals
Metallic Bond
Sharing of a sea of electrons amongst lattice of positive ions
Metallic Bond
Bond where two atoms share a pair of electrons
Covalent Bond
Examples of Covalent Bond
H2, O2, H2O, Methane
Examples of Secondary Bonds
Secondary bonds are weak bonds. Examples are Hydrogen Bond and Van der Vaals Bond
Two uncharged atom weakly attract each other
Van der Vaals Bond
Interactions between charged group of ions
Electrostatic Interaction
Electrostatic Interactions between oppositely charged groups within or between biomolecules
Salt Bridge
Nucleophilic attack by water
Hydrolysis
Proton Donors
Acids
Examples of Strong Acids
HCl, H2SO4
Completely dissociates in strong acidic solutions
Strong Acids
Partially dissociates in acidic solutions
Weak acids
Proton acceptors
Bases
Examples of Strong bases
KOH, NaOH
Example of weak base
CaOH
Used to calculate the concentration of [H+]
Dissociation constant (Ka)
What is pKa?
pKa is the pH at which the protonated and unprotonated species are present at equal concentrations
pKa = -logKa
T or F. The lower the pKa, the higher the Ka
True. The higher the Ka, the greater the tendency to separate solutions into ions. The stronger the acid, the lower its pKa value
Acids with more than one dissociable group
Diprotic acids
What influences the dissociation of Hydrogen?
pH
Example of Diprotic Acids
Carboxyl and Amino
What is Kw?
Kw is the dissociation constant of water. Kw is equal to 10-14 (mol/L)2 for all aqueous solutions, even solutions of acids or bases
T or F. At higher temperature, Kw decreases.
FALSE. At lower temperatures, Kw decreases; at higher temperatures, Kw increases
Describes the behavior of weak acids and buffers
Henderson-Hasselbach Equation
Give the Henderson-Hasselbach equation
pH = pKa + log[A-]/ [HA]
pH measure the ?
Acidity
T or F. The stronger the acid, the lower its pKa value.
TRUE.
What are the factors affecting pKa of a weak acid
Presence of a nearby electron-withdrawing or electron-donating group
T or F. The presence of an adjacent negative charge hinders the release of a proton
True
What is the “dielectric constant of a medium”
The effect of pKa may be observed by adding ethanol to water
(pKa increases in carboxylic acid whereas that of an amine decreases because ethanol decreases the ability of water to dissolve a charged species)
Resist a change in pH
Buffers
Normal arterial blood pH
7.35-7.45
Produces carbonic acid (the major acid produced in the body)
Carbonic anhydrase
How does Carbonic Anhydrase produce carbonic acid?
By dissociation of CO2 and H2O and will form bicarbonate as an effective buffer system
How much fold for a change in 1 pH unit?
10-fold
pH for Severe Acidosis
7.0 blood pH
Universal Solvent
Water
