BCH4024 TEST 1 QUESTIONS WITH COMPLETE SOLUTIONS
Isoelectric Point of Amino Acids - Answer-At the isoelectric point (pI = pH), average charge equals 0
The Henderson-Hasselbalch Eqn. can be applied at pI for both equilibrium dissociations.
Two dissociation reactions involve the net zero charge ...
Isoelectric Point of Amino Acids - Answer-At the isoelectric point (pI = pH), average
charge equals 0
The Henderson-Hasselbalch Eqn. can be applied at pI for both equilibrium
dissociations.
Two dissociation reactions involve the net zero charge species
HAH+ <--> HA + H+
HA <--> A- + H+
(Isoelectric Point of Amino Acids)
Two Henderson-Hasselbalch equations
can be summed to solve for pI. - Answer-2pI=pKa1+ pKa2 +log [HA] +log[A-]
= pKa1 + pKa2 + log [HA][A- ] [HAH+ ][HA]
Cancelling out [HA] gives,
2pI=pKa1+pKa2 +log [A−] [HAH+]
At the pI, [A-] = [HAH+] , such that,
pI=( pKa1+pKa )
Proteins play important role by - Answer-*Structural elements - collagen, histones, etc.
*Enzymes - catalysts needed for metabolism
*Antibodies - needed for immune surveillance
*Receptors & Channels - signal transduction
*Transporters - needed for cell import/export
*Molecular Motors - needed for force generation
*Transcription Factors - needed for gene control
how Most proteins adopt compact (globular) form - Answer-• Requires regular packing
of constituent atoms
• 3-D structure is needed for biological activity
Intrinsically Disordered Proteins - Answer-These proteins often gain a regular 3-D
structure only after they bind to well-folded proteins.
,Peptide Bond - Answer-A molecule of water is released for each peptide bond formed.
• The product is called a peptide (e.g. dipeptide).
• The remaining portion of AA in the peptide is called an amino acid residue.
• Note: The N-terminal and C- terminal ends are available for further reaction.
This peptide-forming reaction is catalyzed by the - Answer-ribosome
four hierarchical levels of protein structure - Answer-primary
secondary
tertiary
quaternary
Michaelis-Menten Equation - Answer-
Vm - Answer-is not a constants.because value depends on total enzyme concentration.
turnover number - Answer-units'='sec^-1
kcat=the frequency of catalysis
The turnover number (or kcat) is a measure of catalytic efficiency.
Michaelis constant - Answer-Km is a kinetic parameter
Km=(k2 +k3)/k1
Km = Kd only when - Answer-k2 >> k3
T or F
Km is the measure of affinity? - Answer-False
Kd - Answer-
Kinetic studies of reaction mechanisms - Answer-To understand an enzyme's
mechanism by measuring how reaction rate changes as a function of various
experimental parameters (e.g.?[S], [E], pH, [Metal Ion], [Coenzyme], etc.).
irreversible inhibitors - Answer-form stable covalent bond.
substrate cannot come up makeing dead enzyme.
E + I <--> EI → E-I
competitive inhibition - Answer-reversible
Noncompetitive inhibition - Answer-
Uncompetitive inhibition - Answer-reversible
, Metabolism involves both synthesis and degradation by - Answer-anabolic pathways
catabolic pathways
Enzymes regulation, three types - Answer-allosteric
..
Bioenergetics - Answer-the study of energy transduction in living systems. how the
energy flows.
biological energy transformation obey standard laws of thermodynamics which are -
Answer-first law of thermodynamics: energy may change form, and may be transported,
but cannot be created or destroyed
second law of thermodynamics:entropy (randomness) of the universe (reacting system
and its surroundings) always increase.
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
-Allows proteins & nucleic acids to fold & unfold
four types of noncovalent (weak) interaction among biomolecules in aques solvent -
Answer-1. hydrogen bonds between neutral groups and peptide bonds
2. ionic interactions such as attraction and repulsion
3. hydrophobic interactions
4. van der waals interactions
Gibbs Free energy (ΔG)
Strengths of Noncovalent Interactions - Answer-(-) to make;; (+) to break
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