Chapter 2: Water Flashcards
____________ gives water its unusual properties
Hydrogen bonds
What is the dissociation energy for hydrogen bonds
23Kj/mol
______________ are responsible for water high melting point due to the thermal energy need to break the bonds
Hydrogen Bonds
Water forms ____________ with polar solutes
Hydrogen Bonds
Hydrogen bonds are strongest when the bonded molecules are oriented in a _______________
Straight line
Water interacts electrostatically with _________ solutes
Charged
Polar molecules are __________
hydrophilic
Nonpolar molecules are ___________
Hydrophobic (such as lipids and waxes)
The strength/ forces of ionic interactions in a solution depends on the what formula
F= Q1 Q/Er2 (E for water at 25 Celsius is 78.5)
For every nonpolar solvent benzene E is ______
4.6
Ionic interaction between dissolved ions are much stronger in less __________ environments
polar
Nonpolar gases such as CO2, O2, & N2 are poorly in ________
Water
Polar gases such as NH3, NO, H2S dissolve easily in ___________
Water
Amphipathic
Compounds containing regions that are both polar & nonpolar regions
Hydrophobic effect
When the nonpolar regions of the molecules cluster together to make the smallest hydrophobic area to the aqueous solvent & the polar region are arranged to maximize their interaction with the solvent (in an amphophilic compounds)
Micelles
Are the stable structures of amphipathic compounds in water
Noncovalent interactions
Are hydrogen bonds, ionic bonds, hydrophobic &van der waals interactions (weaker than covalent bonds)
__________ are crucial to macromolecular structure & function
Weak interactions
Interactions driven by the ______________ are also much weaker than convalent bonds
Hydrophobic effect
Hydrophobic interactions
Forces that hold nonpolar regions of the molecules together
______________ effect the colligative properties of aqueous solutions
Solutes
Water tends to move from ________ to ______ concentrations
High to low
When water molecules move from high to low concentrations they produce _____________
Osmotic pressure
Osmotic pressure
Is the force needed to resist water movement
Osmotic pressure equation:
∏= icRT
Osmosis
Water movement across a semipermeable membrane driven by difference in osmotic pressure
Isotonic solution
When the solution of osmolarity is equal to the outside of the cell (doesnt gain or lose water)
Hypertonic solution
Higher osmolarity than the outside of the cell, the cell shrinks as water moves out
Hypotonic solution
Lower osmolarity than the outside of the cell, the cell swells as water moves in
Osmotic lysis
Bursting of a cell
The ionization of water is expressed by an ______________
Equilibrium constant
Kw is what
The ion product of water at 25 Celius
At 25 Celius Kw value is what ?
1 x 10-14 M2
Neutral pH
When there are equal concentrations of H+ & OH-
pH equation is what?
pH= -log{[H+] (when pH is greater than 7 its basic & when its lower than 7 its acidic)
When pH is below 7.4 its called ________ & when its above 7.4 its called ________
acidosis, alkalosis
_______ are proton donors & ________ are proton acceptors
Acids, Bases
What is the pKa equation?
pKa = -log Ka (the stronger the acid the lower the pKa)
_________ reveal the pKa of a weak acid
Titrations curves
A tritration curve is pH on the _____ axis & base added (usually NaOH) on the _____ axis (it shows the pKa of a weak acid)
y, x
_________ are mixtures of weak acids & their conjugated bases
Buffers
Buffers
Are aqueous systems that tend to resist changes in pH when small amounts of acid (H+) or base (OH-) are added
The midpoint of the titration curve (the pH value) & 1 pH unit out is the ____________ region
Buffering
During the buffering region whether H+ or OH- is added the pH barely _______
Change (stays the same basically)
The _________________ equations relates pH, pKa, & buffer concentration
Henderson-Hasselbalch equation
What is the Henderson-Hasselbalch equation?
pH=pKa + log [H+]/[HA]
The pKa of a weak acid is equal to the _____ of the solution at the midpoint of a titrations curve
pH
Weak acid or bases buffer cells & tissues against _____ change
pH
The two important biological buffers are the ____________ & ____________ systems
Phosphate & bicarbonate systems
The phosphate system act in the _______ of the cell consist of H2PO4- as proton donor & H2PO42- as proton acceptor
Cytoplasm
The phosphate buffer system pKa & pH is ________ & resist pH changes between 5.9 & 7.9
6.86
Blood plasma is buffered in part by the ________ system which has carbonic acids HCO3- (Proton donor) & bicarbonate (HCO-) (as proton acceptor)
Bicarbonate
____________ buffer system is an effective buffer when the pH = 7.4
Bicarbonate
H2CO3 pKa at 37 Celius is what?
3.57
Condensations reactions
Water is eliminated
Hydrolysis reactions
Cleavage accompanied by the addition of the elements of water
Hydrolases
Hydrolysis reaction catalyze by enzymes (are exergonic & they produce two molecules from one)
