Exam 1: pH Flashcards
A protein critical for maintaining the blood pH is ____; when the blood pH begins to rise, ____________.
A) Hemoglobin; more carbonic acid is excreted.
B) Carbonic anhydrase; less CO2 is exhaled.
C) Myoglobin; less CO2 is exhaled.
D) Carbonic anhydrase; more protons combine with bicarbonate.
B) Carbonic anhydrase; less CO2 is exhaled.
Which of the following peptides binds most tightly to a cation exchanger at pH 7.0? Note that a cation exchange itself is negatively charged.
A) MDECKNPYNCQ
B) IDLSNGPTRLYS
C) MRCKSNLHYNP
D) ELSDIRNEPGDY
C) MRCKSNLHYNP
Which of the following electrophoresis techniques requires the usage of a gel with a stable pH gradient?
A) SDS-PAGE
B) Agarose gel
C) Isoelectric focusing
D) Native gel electrophoresis
C) Isoelectric focusing
Raising pH from 7 to 10 can drastically reduces the amount of DNA in double helical form. Which of the following provides a correct explanation for this phenomenon?
A) Raising pH from 7 to 10 promotes the binding of RNA to DNA to form a three-stranded structure.
B) Raising pH from 7 to 10 impairs the correct hydrogen bond formation between base-pairs.
C) Raising pH from 7 to 10 leads to increased protonation of guanine in DNA.
D) Raising pH from 7 to 10 increases binding of water molecule to single-stranded DNA.
B) Raising pH from 7 to 10 impairs the correct hydrogen bond formation between base-pairs.
Proper surface charge distribution is important for the function of a protein. How would altering pH of a solution affect the surface charge distribution of a protein?
A) Increasing pH would lead to more positive charges on the surface of a protein.
B) Increasing pH would lead to more negative charges on the surface of a protein.
C) Decreasing pH would lead to more negative charges on the surface of a protein.
D) Decreasing pH would promote a shift of negative charges from the interior of a protein to its surface
B) Increasing pH would lead to more negative charges on the surface of a protein.
Which of the following helps to maintain pH in living system in physiological range?
A) Proteins with a lot of histidine residues
B) Pyruvate
C) Acetate
D) All of the above
A) Proteins with a lot of histidine residues
Arginine has an isoelectric point of 10.8. What would the charge status of arginine at pH 2.0, pH 7.0, and pH 12 be, respectively?
A) positively charged; positively charged; negatively charged
B) positively charged; neutral; negatively charged
C) negatively charged; negatively charged; positively charged
D) negatively charged; neutral; positively charged
A) positively charged; positively charged; negatively charged
On an anion-exchange column, which of the following peptides binds most tightly to the beads at pH 7.0?
A) CDEFGHIKLMN
B) DEFGHIKLMNK
C) EFGAISLMNDE
D) GHIKLMNFILR
C) EFGAISLMNDE
Aspirin is a weak acid with a pKa of 3.5. In its base form, aspirin carries a net negative charge and is hard to pass the lipid bilayer. After taken orally, in which of the following compartments of the GI tract does aspirin have the least possibility to be absorbed into the bloodstream due to its acid/base property?
A) The compartment with a pH about 2
B) The compartment with a pH about 3.5
C) The compartment with a pH about 7
D) Its absorption is not impacted by the pH
C) The compartment with a pH about 7
Decreasing pH of a solution tends to have the following effect to the proteins in the solution:
A) Increasing the protonation of the protein molecules, resulting in increased positive charges
B) Decreasing the protonation of the protein molecules, resulting in increased negative charges
C) Allowing the protein molecules to reach their isoelectric points
D) Allowing the protein molecules to deviate away from their isoelectric points
A) Increasing the protonation of the protein molecules, resulting in increased positive charges
