BCH4024 EXAM 1 PURICH REVIEW
QUESTIONS WITH 100% CORRECT
ANSWERS
UV light Absorption by Aromatic Amino Acids and Proteins - Answer-Tryptophan
absorbs the most UV light bc it has the largest p orbital highway. Tyrosine is next
followed by phenylalanine.
Characterisation of biomolecules by a spectrophotomer (ref slide--good to know) -
Answer--Uses light absorption of aromatic side chains to detect presence and quantify
concentration
-Beer lambert law- c=Abs/(el)
Where Abs-log (Incidence light intensity/Transmitted light intensity)
-Absorption at 280nm by tryptophan>tyrosine>phenylalanine
-1-2% AAs are aromatic so abs of 1 at 280nm= 1mg/ml of protein
Cysteine and Cystine - Answer--free SH group in cysteine ionizes and is largely
undissociated at physiologic pH
-SH groups oxidize to form disulfide bonds in cystine
-cysteine is the reduced form (e in cysteine is one more electron, a characteristic of a
reduced compund) and is found in the cytoplasm
-cystine: mainly present in circulation; oxidized form and found circulating our blood or
in extracellular regions
-cystine is formed as two cysteine molecules come together; C-peptide bonds form
cystine bond until S-S bond is made; once made, C-peptide bond is released
How do we measure one's insulin production? - Answer--indirectly
-as a byproduct of insulin formation, C-peptide is released and we can measure this
conecntration to see how much insulin is produced
-insulin is constantly created/destroyed so we cannot keep an accurate account so we
indirectly measure their C-peptide conc.
-someone with lots of insulin would have high levels of C-peptide
-Insulin is very short-lived; so serum C-peptide is best measure of insulin formation
Importance of S-S bonds - Answer--antibody structures are stabilized by S-S bonds
without S-S linkages,
-Antibody (Ab) could not bind to antigen
-Ab would dissociate and would be squeezed out of circulation
-Ab could not cross-link and agglutinate antigen-bearing cells
, Amphipathic compounds - Answer--Simaltaneously contain an acidic and basic group in
a zwitterion ("between")
-Zwitterions exist over a large pH range
-Neutral form is the minor species (nonionic form)
-COO- is the first to deprotonate at low pH and NH3+ last at high pH
Ionization of AA - Answer--charge on amino acid depends on soln pH
-we begin at low pH (fully protonated) and add OH- (removing acidic protons first)
-strongest Acids have weakest proton affinity and lose their H+ first
-strongest bases have strongest proton affinity and lost their H+ last
-WE REMOVE ACIDIC PROTONS FIRST
Isoelectric Point of AA - Answer--pH where AA has average charge=0
-pH=pKa at the pI
-PRACTICE DERIVED THE EQUATION (practice problems and calculating PI)
2pI=pKa1 + pKa2 + log[HA]/[HAH+] + log[A-]/[HA]
pI=pKa1+pKa2/2
Binding Interactions - Answer--computers use binary code: 1's & 0's
-biology uses bound & unbound states (ligate=to join)
-Ligand (L)=defined as any molecule that binds to binding sites on receptors, transport
proteins or enzymes.
-association reaction:
P+L--> P*L (reversible reaction noted by the astrict or dot)
-dissociation reaction: P*L--> P+L
Ligand examples - Answer-Enzyme substrates; receptor agonists &antagonists,
metabolites, metal ions, protons, and proteins
Dissociation rxns - Answer--biochemists prefer dissociation reactions
-Kd=[P][L]/[P.L] (products/reactants); units=Molarity
-High Kd=weak binding
-Low Kd=strong binding
-extent of binding on the lligand conc. and the value of dissociation constant
Ligand- Protein binding
(PRACTICE DERIVING EQN) - Answer--A ligand is a small molecule that binds to
defined regions on receptors and enzymes known as binding/active sites
-Extent of binding depends on ligand conc and equilibrium dissociation constant
Kd=[P][L]/[P.L]
[Ptot]=[P]+[P.L]
subs [P] and divide by [P.L] to get...
[Ptot]/[P.L]=Kd/[L]+1
QUESTIONS WITH 100% CORRECT
ANSWERS
UV light Absorption by Aromatic Amino Acids and Proteins - Answer-Tryptophan
absorbs the most UV light bc it has the largest p orbital highway. Tyrosine is next
followed by phenylalanine.
Characterisation of biomolecules by a spectrophotomer (ref slide--good to know) -
Answer--Uses light absorption of aromatic side chains to detect presence and quantify
concentration
-Beer lambert law- c=Abs/(el)
Where Abs-log (Incidence light intensity/Transmitted light intensity)
-Absorption at 280nm by tryptophan>tyrosine>phenylalanine
-1-2% AAs are aromatic so abs of 1 at 280nm= 1mg/ml of protein
Cysteine and Cystine - Answer--free SH group in cysteine ionizes and is largely
undissociated at physiologic pH
-SH groups oxidize to form disulfide bonds in cystine
-cysteine is the reduced form (e in cysteine is one more electron, a characteristic of a
reduced compund) and is found in the cytoplasm
-cystine: mainly present in circulation; oxidized form and found circulating our blood or
in extracellular regions
-cystine is formed as two cysteine molecules come together; C-peptide bonds form
cystine bond until S-S bond is made; once made, C-peptide bond is released
How do we measure one's insulin production? - Answer--indirectly
-as a byproduct of insulin formation, C-peptide is released and we can measure this
conecntration to see how much insulin is produced
-insulin is constantly created/destroyed so we cannot keep an accurate account so we
indirectly measure their C-peptide conc.
-someone with lots of insulin would have high levels of C-peptide
-Insulin is very short-lived; so serum C-peptide is best measure of insulin formation
Importance of S-S bonds - Answer--antibody structures are stabilized by S-S bonds
without S-S linkages,
-Antibody (Ab) could not bind to antigen
-Ab would dissociate and would be squeezed out of circulation
-Ab could not cross-link and agglutinate antigen-bearing cells
, Amphipathic compounds - Answer--Simaltaneously contain an acidic and basic group in
a zwitterion ("between")
-Zwitterions exist over a large pH range
-Neutral form is the minor species (nonionic form)
-COO- is the first to deprotonate at low pH and NH3+ last at high pH
Ionization of AA - Answer--charge on amino acid depends on soln pH
-we begin at low pH (fully protonated) and add OH- (removing acidic protons first)
-strongest Acids have weakest proton affinity and lose their H+ first
-strongest bases have strongest proton affinity and lost their H+ last
-WE REMOVE ACIDIC PROTONS FIRST
Isoelectric Point of AA - Answer--pH where AA has average charge=0
-pH=pKa at the pI
-PRACTICE DERIVED THE EQUATION (practice problems and calculating PI)
2pI=pKa1 + pKa2 + log[HA]/[HAH+] + log[A-]/[HA]
pI=pKa1+pKa2/2
Binding Interactions - Answer--computers use binary code: 1's & 0's
-biology uses bound & unbound states (ligate=to join)
-Ligand (L)=defined as any molecule that binds to binding sites on receptors, transport
proteins or enzymes.
-association reaction:
P+L--> P*L (reversible reaction noted by the astrict or dot)
-dissociation reaction: P*L--> P+L
Ligand examples - Answer-Enzyme substrates; receptor agonists &antagonists,
metabolites, metal ions, protons, and proteins
Dissociation rxns - Answer--biochemists prefer dissociation reactions
-Kd=[P][L]/[P.L] (products/reactants); units=Molarity
-High Kd=weak binding
-Low Kd=strong binding
-extent of binding on the lligand conc. and the value of dissociation constant
Ligand- Protein binding
(PRACTICE DERIVING EQN) - Answer--A ligand is a small molecule that binds to
defined regions on receptors and enzymes known as binding/active sites
-Extent of binding depends on ligand conc and equilibrium dissociation constant
Kd=[P][L]/[P.L]
[Ptot]=[P]+[P.L]
subs [P] and divide by [P.L] to get...
[Ptot]/[P.L]=Kd/[L]+1
