Biochem 1: Water, pH, buffers Flashcards
water structure and special properties
- polar molecule
- forms hydrogen bonds
- tetrahedral shape
bonds each water molecule can be involved with
- 4 hydrogen bonds
- 2 as a donor, 2 as acceptor
what is important about hydrogen bonding
even though hydrogen bonds are weaker than covalent bonds, they have a significant effect on the physical properties of hydrogen-bonded compounds
hydrophilic interactions
“water-loving”
- a polar molecule that interacts with water
- interact through weak attractions of hydrogen bonds
hydrophobic interactions
“water-fearing”
- a nonpolar molecule that aggregates with other non polar molecules
- hydrocarbon molecules
an aqueous solution
solvent is water
-most biochemical reactions occur in aqueous solutions
solvent properties in water
hydrophobic
tend to not dissolve in water
solvent properties in water
hydrophilic
tend to dissolve in water
amphipathic
has characteristics of both properties
-molecules that contain one or more hydrophobic and one or more hydrophilic regions
amphipathic molecules interactions
-both polar and non polar character
-interaction between non polar molecules is very weak
(Called van der Waals interactions)
when some substances dissolve in water, they release
protons
-these H+ molecules can interact with other molecules and change their properties
what is a micelle
a spherical arrangement of organic molecules in water solution clustered so that
- their hydrophobic parts are buried inside the sphere
- their hydrophilic parts are on the surface of the sphere and in contact with the water environment
an acid:
releases hydrogen ions (H+) when dissolved in solution
a base:
accepts hydrogen ions (H+) when dissolved in solution
strong acid/base
fully ionizes in water
weak acid
not all the acid molecules dissociate into ions
weak base
can accept a H+ ion
acid-base reactions may be _____
reversible
ionization of strong acids and bases is
irreversible
ionization of weak acids and bases is
somewhat reversible
water acts as both a
weak acid and a weak base
water has a tendency to
ionize
what is Ka
numerical measure for acid strength, the acid dissociation constant
the higher the value of the Ka, the ____ the acid
stronger
in biochemistry, most of the acids encountered are
weak acids (Ka well below 1)
the lower the value of pKa, the ____ the acid
stronger
pH is the measure of
hydrogen ion concentration
the negative logarithm of the molar concentration of H+ ions
H+ concentration of pure water is
10^-7 M
lower pH numbers mean
higher H+ concentration or greater acidity
what can pH influence
the rate of biological reactions and can change the 3 dimensional structure of biological molecules, which impacts function
Henderson-Hasselbalch equation connects
Ka to pH of a solution containing both acid and base
using HA, weak acid and A-, conjugate base ratio
in Henderson-Hasselbalch,
pH < pKa means
weak acid predominates
in Henderson-Hasselbalch,
pH > pKa means
conjugate base predominates
titration is
an experiment in which measured amounts of acid (or base) are added to measured amounts of base (or acid)
buffer
a solution whose pH resists change upon addition of acid or base
(consists of a weak acid and its conjugate base)
-helps maintain stable pH
hyper-ventilation can results in increased blood pH, resulting in
respiratory alkalosis
hypo-ventilation can result in decreased blood pH, resulting in
respiratory acidosis
