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Lecture 5

BIOL 1001 Lecture Notes - Lecture 5: Chemical Polarity, Drain Cleaner, Logarithmic ScalePremium


Department
Biology
Course Code
BIOL 1001
Professor
Gregory S.Smutzer
Lecture
5

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BIOL 1001 Lecture 5 Bonds
Water Is A Molecule With Covalent Bonds
Special Properties of Water
Temperature Stabilizing - has high specific heat
High surface tension - cohesive due to hydrogen bonding
Good solvent - polarity of water allows it to dissolve polar molecules
Water loving molecules = polar molecules
The pH Scale
Water can be acidic, neutral, or basic if it loses a proton (OH-), or gains a proton
(hydrogen nucleus)
Self-ionization of water is the process that determines the pH of water (1 x 10^-7 ions)
Measures H+ concentration of fluid
Change of 1 on scale means 10x change in H+ (proton) concentration
pH Scale is a logarithmic scale
0 ——— 7 ——— 14
Acidic Neutral Basic
Acids & Bases
Acids (Sulfuric acid is in car batteries)
o Donate H+ (this is a proton which is a hydrogen nucleus with no electrons) when
dissolved in water
o Acidic solutions have pH < 7.0
Bases (sodium hydroxide is in drain cleaner)
o Accept H+ (protons) when dissolved in water
o Releases -OH ions when dissolved in water
o Basic solutions have pH > 7.0
o Cytoplasm of cells has pH of 7.40
Buffer Systems
Minimize shifts in pH
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Partnership between a weak acid and base it forms when dissolved
example of weak base = canonic acid in blood
Carbonic Acid Bicarbonate Buffer System
H20 + CO2 > H2CO3 (Carbonic acid. occurs naturally, plus enzyme carbonic anhydrase
is used to form C Acid)
when blood pH rises (more basic), carbonic acid (weak acid on left) dissociates to form
bicarbonate & H+
o H2CO3 > HCO3- + H+
When blood pH drops, bicarbonate binds H+ to form carbonic acid to remove protons
from blood
o HCO3 - + H+ > H2CO3
When blood pH rises above 7.40, this happens:
H2CO3 > HCO3 - + H+
When pH decreases, this happens:
HCO3 - + H3 > H2CO3
Salts
Compounds that release ions other than H+ (protons) and OH- (hydroxyl groups) when
dissolved in water
Ex. NaCl releases Na+ and Cl-
o CaCl2 is rock salt, and releases Ca2+ and 2 Cl- ions
many salts dissolve into ions that play important biological roles
these coins can act as blood electrolytes
Acid and base yield a salt and water
HCl + NaOH > NaCl + H20
o HCl = hydrochloric acid
o NaOH = sodium hydroxide (a base)
o NaCl = sodium chloride (a salt)
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