BCH4024 EXAM 1 CERTIFICATION
QUESTIONS WITH COMPLETE
SOLUTIONS
what is life? - Answer-a complex self-adaptive system, able to evolve and gain options.
the search algorithm for change - Answer-Mutation
Dissociation Dynamics at Equilibrium - Answer-Water undergoes rapid H+
dissociation/reassociation
no free H+;
instead H+ combines with a
neighboring H2O to form
hydronium ions, H3O+
In liquid H2O, protons actually "hop".
proton Hop - Answer-water accepts protons and becomes a hydronium ion, Hydronium
ion gives up a proton (HOP)
pH and Acid/Base Rxn definition - Answer-pH = - log[H3O+]
Kw = [H3O+][OH-] = 10^-14 M^2
neutrality requires - Answer-[H3O+] = [OH-] = x
pH and Acid/Base Rxn definition impractical? - Answer-because pH meters don't
measure [H+].
They measure proton activity (H+), where A is
the activity coefficient, and (H+) = A[H+].
H+?
A? - Answer-(H+) = Proton activity
(A) = Activity coefficient
(H+)=A(H+)
Henderson-Hasselbalch Equation - Answer-pH = pKa + log ([A-]/[HA])
when pH = pKa - Answer-[A-] = [HA]
,when pH = pKa + 1 - Answer-[A-] = 10 x [HA]
when pH = pKa - 1 - Answer-[A-] = 0.1 x [HA]
Basic or acidic?
[HA] < [A-] - Answer-Basic
Basic or acidic?
[HA] > [A-] - Answer-Acidic
Why is it incredibly important
to understand biochemical processes - Answer--many metabolites have acid or base
groups
-Enzymes have acids and bases in active sites
-DNA and RNA are polyelectrolytes
Buffers - Answer-**Weak Acids & Weak Bases help to stabilize pH
**They obey Le Chatelier's Principle:
"a dynamic system compensates to a stress"
**Add H+ & they readjust: A- + H+ = HA
**Add OH- & they readjust: HA + OH- = A- + H2O
why are buffer most effective near pKa Values? - Answer-because that is where there is
a large pool of both weak acids and conjugate bases
Buffering region by pH lays where? - Answer-between pH 3.76-5.76
biological buffers - Answer-many metabolites are weak acids/bases
-orthophosphate(1-5mM)
-bicarbonate(20-30mM)
-ATP(3-25mM)
-proteins(300 gL)
in muscle, creatine-phosphate (60 mM)
Bicarbonate buffer system - Answer-the most important buffer system for acid-base
homeostasis in humans
-takes full adv. of CO2 production
-maintains constant plasma pH by countering changes in acids, bases, anions, metal
ion, etc
-(CO2) with (H2O) form (H2CO3), dissociates to form hydrogen ion and (HCO3-)
, (Rxn is catalyzed by carbonic anhydrase)
-blood has excess hydrogen ions (acidosis), protons shift the Equilibrium in favor of
H2O and CO2, minimizing the acidity
-system becomes powerful acid-base regulator when coupled with respiratory
compensation (altered breathing rate modifies circulating CO2)
Increasing Breathing Rate - Answer--when one expels excess CO2, resulting in
respiratory alkalosis.
-Pulls protons toward production of CO2
-Excess acid is exhaled
Cells also buffer extracellular fluid (ECF) - Answer-In acid-base disturbances, shifts of
(H+) or (HCO3-) between cells and ECF are mainly balanced by movements of Na+, K+
and Cl-
Protonation/Deprotonation kinetics in H2O - Answer--protonation/deprotonation of small
molecules is rapid
-diffusion-limited process:
-Protonation and deprotonation of macromolecules
diffusion-limited process: - Answer-reaction rate is determined by how fast reactants
collide
the Protonation and deprotonation of macromolecules? - Answer-acid/base groups on
surface react immediately
acid/base groups deep inside may never ionize
hydrogen bonds of buried helices and beta-sheets require the "conformation breathing"
-local unfolding
Pepsin - Answer-a digestive enzyme secreted into gastric juice, having a pH of 1.5
allowing pepsin to act optimally
Trypsin - Answer-a digestive enzyme that acts in the small intestine, and has a pH
optimum that matches the neutral pH in the lumen of the small intestine.
Alkaline phosphatase - Answer-a hydrolytic enzyme that
operates well enough at neutral pH of intestine.
"Weak"
Noncovalent
Interactions - Answer--Individually weak, but the aggregate
effect is very significant
QUESTIONS WITH COMPLETE
SOLUTIONS
what is life? - Answer-a complex self-adaptive system, able to evolve and gain options.
the search algorithm for change - Answer-Mutation
Dissociation Dynamics at Equilibrium - Answer-Water undergoes rapid H+
dissociation/reassociation
no free H+;
instead H+ combines with a
neighboring H2O to form
hydronium ions, H3O+
In liquid H2O, protons actually "hop".
proton Hop - Answer-water accepts protons and becomes a hydronium ion, Hydronium
ion gives up a proton (HOP)
pH and Acid/Base Rxn definition - Answer-pH = - log[H3O+]
Kw = [H3O+][OH-] = 10^-14 M^2
neutrality requires - Answer-[H3O+] = [OH-] = x
pH and Acid/Base Rxn definition impractical? - Answer-because pH meters don't
measure [H+].
They measure proton activity (H+), where A is
the activity coefficient, and (H+) = A[H+].
H+?
A? - Answer-(H+) = Proton activity
(A) = Activity coefficient
(H+)=A(H+)
Henderson-Hasselbalch Equation - Answer-pH = pKa + log ([A-]/[HA])
when pH = pKa - Answer-[A-] = [HA]
,when pH = pKa + 1 - Answer-[A-] = 10 x [HA]
when pH = pKa - 1 - Answer-[A-] = 0.1 x [HA]
Basic or acidic?
[HA] < [A-] - Answer-Basic
Basic or acidic?
[HA] > [A-] - Answer-Acidic
Why is it incredibly important
to understand biochemical processes - Answer--many metabolites have acid or base
groups
-Enzymes have acids and bases in active sites
-DNA and RNA are polyelectrolytes
Buffers - Answer-**Weak Acids & Weak Bases help to stabilize pH
**They obey Le Chatelier's Principle:
"a dynamic system compensates to a stress"
**Add H+ & they readjust: A- + H+ = HA
**Add OH- & they readjust: HA + OH- = A- + H2O
why are buffer most effective near pKa Values? - Answer-because that is where there is
a large pool of both weak acids and conjugate bases
Buffering region by pH lays where? - Answer-between pH 3.76-5.76
biological buffers - Answer-many metabolites are weak acids/bases
-orthophosphate(1-5mM)
-bicarbonate(20-30mM)
-ATP(3-25mM)
-proteins(300 gL)
in muscle, creatine-phosphate (60 mM)
Bicarbonate buffer system - Answer-the most important buffer system for acid-base
homeostasis in humans
-takes full adv. of CO2 production
-maintains constant plasma pH by countering changes in acids, bases, anions, metal
ion, etc
-(CO2) with (H2O) form (H2CO3), dissociates to form hydrogen ion and (HCO3-)
, (Rxn is catalyzed by carbonic anhydrase)
-blood has excess hydrogen ions (acidosis), protons shift the Equilibrium in favor of
H2O and CO2, minimizing the acidity
-system becomes powerful acid-base regulator when coupled with respiratory
compensation (altered breathing rate modifies circulating CO2)
Increasing Breathing Rate - Answer--when one expels excess CO2, resulting in
respiratory alkalosis.
-Pulls protons toward production of CO2
-Excess acid is exhaled
Cells also buffer extracellular fluid (ECF) - Answer-In acid-base disturbances, shifts of
(H+) or (HCO3-) between cells and ECF are mainly balanced by movements of Na+, K+
and Cl-
Protonation/Deprotonation kinetics in H2O - Answer--protonation/deprotonation of small
molecules is rapid
-diffusion-limited process:
-Protonation and deprotonation of macromolecules
diffusion-limited process: - Answer-reaction rate is determined by how fast reactants
collide
the Protonation and deprotonation of macromolecules? - Answer-acid/base groups on
surface react immediately
acid/base groups deep inside may never ionize
hydrogen bonds of buried helices and beta-sheets require the "conformation breathing"
-local unfolding
Pepsin - Answer-a digestive enzyme secreted into gastric juice, having a pH of 1.5
allowing pepsin to act optimally
Trypsin - Answer-a digestive enzyme that acts in the small intestine, and has a pH
optimum that matches the neutral pH in the lumen of the small intestine.
Alkaline phosphatase - Answer-a hydrolytic enzyme that
operates well enough at neutral pH of intestine.
"Weak"
Noncovalent
Interactions - Answer--Individually weak, but the aggregate
effect is very significant
