Biochem Final Flashcards
The shift from the deoxy to the oxy state of hemoglobin happens simultaneously in all binding sites, even if some of these sites don’t have oxygen present. T or F
True
In the structure of Oxy-myoglobin, 4 ligands are bound to iron from the heme, one from the protein, and the 6th ligand is provided by the distal histidine. T or F
False
The hydrogen bonding pattern in a beta sheet occurs between beta strands rather than within the same strand. T or F
True
A biochemical reaction (A converted to B) has a delta G = -116 kJ/mol. Which of the following can you conclude about this reaction?
a. The reaction does require thermodynamic coupling.
b. The delta H (enthalpy change is likely to be small.
c. The reaction does not require thermodynamic coupling.
d. The delta S is likely to be the driving force of the reaction.
c. The reaction does not require thermodynamic coupling.
A mutation in several cultured cells renders their ribosomes unable to include proline in any amino acid sequences. Which one of the following would be unaffected by this mutation?
a. Tropocollagen production.
b. Production of proteins containing beta-turns in their secondary structure.
c. Amphipathic alpha-helix production.
c. Amphipathic alpha-helix production.
A positive delta S for water is the driving force behind the tendency of nonpolar molecules to self-associate, otherwise known as the hydrophobic effect. T or F
True
Which structural technique does not work well for studying large proteins?
a. NMR spectroscopy
b. Structural prediction
c. X-ray crystallography
d. SDS page
e. Cyro-EM
a. NMR spectroscopy
Fibroin is composed of stacks of beta sheets made of a hydrophobic 7 residue pseudo repeat in which every third residue is nonpolar. T or F
False
Flattening of the heme plane (upon binding to oxygen) is the basis of positive cooperativity in hemoglobin. T or F
True
In exclusion chromotography, small proteins elute before big proteins. T or F
False
The primary role of the distal histidine in Myoglobin is to:
a. Provide favorable delta H interactions to help the protein fold.
b. Promote positive cooperativity through allostery.
c. Promote oxygen binding via a hydrogen bond
d. Hold the heme in place by forming a covalent bond with the iron.
c. Promote oxygen binding via a hydrogen bond.
Which of the following is not an example of heterotropic regulation of hemoglobin?
a. Low pH resulting in the stabilization of the deoxy state of hemoglobin
b. The Bohr effect.
c. 2,3-BPG binding to the deoxy state of hemoglobin
d. Oxygen binding to alpha1 chain of hemoglobin.
d. Oxygen binding to alpha1 chain of hemoglobin.
A solution of carbonic acid (pKa=6.37) that is set to a pH of 8.0 is at its maximum buffering capacity (i.e., most effective at resisting changes in pH). T or F
False
A solution of L-cysteine at 50 mM concentration is adjusted to a pH of 5. What is the net charge of L-cysteine in this solution? (chart is shown)
a. -1
b. +1
c. +2
d. 0
d. 0
Among all the amino acids with an ionizable side chain, histidine is unique in which way? (chart is given)
a. It is small in comparison to the aromatic amino acids.
b. It can be covalently linked in the active site of some enzymes.
c. It can dissociate a proton near physiological pH.
d. It is the only titratable amino acid that has a ring structure on its side chain.
c. It can dissaciate a proton near physiological pH.
Hydrogen bonding is used to stabilize which of the following?
a. Intrinsically disordered proteins.
b. Beta turns
c. Disulfide bonds
d. Van der Waals interactions
b. Beta turns
What is the purpose of the amphipathic detergent in SDS PAGE?
a. Ensure that proteins are positively charged, and therefore migrate on the acrylamide matrix.
b. Ensure that proteins remain folded during electrophoresis.
c. Ensure that the disulfide bonds in a protein are all reduced.
d. Ensure that proteins are negatively charged, and therefore migrate on the acrylamide matrix.
d. Ensure that proteins are negatively charged, and therefore migrate on the acrylamide matrix.
You try to purify a protein using ion exchange chromatography, but you find that your protein did not “stick” to the column. What is a possible cause?
a. The protein has no affinity tag.
b. The protein was too big to enter the column matrix.
c. The pH of the buffer puts the protein close to its isoelectric point.
d. The protein is misfolded.
c. The pH of the buffer puts the protein close to its isoelectric point.
A chemical reaction is found to have an equilibrium constant (Keq) that is very, very small. Which of the following can you conclude regarding the reaction?
a. The acid involved in the reaction is only partially dissociated.
b. The concentrations of the reactants and products are equal.
c. The concentrations of the reactants are higher than the products.
d. The concentrations of the reactants are lower than the products.
c. The concentrations of the reactants are higher than the products.
A mutation of Myoglobin is discovered that results in stronger binding to oxygen. What can you expect from this new protein?
a. The P50 will decrease.
b. The P50 will increase.
c. This form of myoglobin will be an effective substitute for hemoglobin.
d. The Hill coefficient (nH) will increase.
a. The P50 will decease.
The classic experiment with Ribonuclease A demonstrated which of the following?
a. That disulfides promote misfolded structures of proteins.
b. That using urea to unfold proteins is a useful research tool
c. That the information needed to fold a protein is contained in the primary amino acid sequence.
d. That the information needed to form quaternary structures is contained in the primary amino acid sequence.
c. That the information needed to fold a protein is contained in the primary amino acid sequence.
Which of the following does not stabilize the structure of tropocollagen?
a. Hydroxylation of proline
b. The activity of lysyl oxidase.
c. The hydrophobic effect.
d. Disulfide bonds.
d. Disulfide bonds.
The following amino acid sequence is ⍺ helical. How many separate ⍺ helices are there? MAKLLGVEPETVHELAAHVDAAMSVCSTAEIGDDVVIAWTALSARSPAFLSITSANFDS
a. 4
b. 5
c. 3
d. 2
c. 3
An enzyme catalyst can only change which of the following?
a. hydrophobic effect
b. ΔG°‡
c. Keq
d. ΔG°
b. ΔG°‡