EXAM II Flashcards
Which of the following is true about membrane proteins?
a) Integral membrane proteins span the membrane as a random coil,
b) Lateral diffusion occurs unless other cellular components restrict their movement.
c) They readily undergo transverse (flip-flop) diffusion every few seconds.
d) They are never glycoproteins.
e) They contain entirely nonpolar amino acids in their primary structure.
b) Lateral diffusion occurs unless other cellular components restrict their movement.
Which of the following statements describes integral membrane proteins?
a) They are easily removed by changes in pH or high salt.
b) The proteins tend to be water-soluble.
c) Amino acids that contact the fatty acid carbon chains of the membranes are hydrophobic.
d) They interact with the membrane via a lipid anchor.
e) None of the above.
c) Amino acids that contact the fatty acid carbon chains of the membranes are hydrophobic.
What type of transport does NOT require the assistance of a membrane protein?
a) facilitated transport
b) simple diffusion
c) passive transport
d) none of the above
b) simple diffusion
Which of the following is NOT true about enzymes?
a) Enzymes catalyze the reaction in only the forward direction.
b) Enzymes are often very specific for their substrates.
c) Enzymes typically catalyze reactions at much higher rates than chemical catalysts.
d) Enzymes typically act under milder conditions of temperature and pH than chemical catalysts.
e) All of the statements given are true.
a) Enzymes catalyze the reaction in only the forward direction.
How many stereoisomers are possible for aldopentose such as ribose?
a) 2
b) 4
c) 8
d) 16
e) 32
c) 8
The protein that forms a Transmembrane pore that allows preproteins to pass through the ER membrane is called the
a) signal recognition particle
b) signal peptidase
c) docking protein
d) translocon
e) none of the above
d) translocon
Which of the following amino acids would provide a side chain capable of increasing the hydrophobicity of a binding site?
a) aspartic acid
b) lysine
c) isoleucine
d) arginine
e) serine
c) isoleucine
What is the velocity of a first order reaction when the reactant concentration is 610^(-2) M and the rate constant is 810^3 s^(-1)?
a) 1.3310^5 M^(-1) s^(-1)
b) 1.3310^5 M s^(-1)
c. ) 7.510^(-2) M s^(-1)
d. ) 4.810^2 M s^(-1)
e. ) not enough data are given here to make this calculation
d.) 4.8*10^2 M s^(-1)
Which of the following is NOT a characteristic of the (Na^+-K^+)-ATPase?
a. ) Antiporter
b. ) It transports 3 Na^+ ions out of the cell and 2 K^+ ions into the cell.
c. ) Transport is coupled to the hydrolysis of ATP
d. ) Transport occurs against a concentration gradient
e. ) None of the above
e.) None of the above
Chymotrypsin preferentially cleaves a peptide bond adjoining a bulky, nonpolar side chain because chymotrypsin’s “specificity pocket”
a) contains a sulfhydryl group that forms a disulfide bond with the substrate
b) is lined with small hydrophobic side chains, leaving considerable room in the pocket and making it nonpolar
c) contains a negative charge
d) is mostly filled with large side chains
e) is positively charged
b) is lined with small hydrophobic side chains, leaving considerable room in the pocket and making it nonpolar
If you add an enzyme to a solution containing only the product (P) of the reaction R ↔ P, would you expect any R to form?
a. ) Yes, because the enzyme reduces the standard free energy change for the reaction
b. ) No, because the enzyme lowers the transition state energy barrier
c. ) No, because product inhibits the enzyme
d. ) No, because enzymes only catalyze the forward reaction
e. ) Yes, because the reaction proceeds backwards until reaching equilibrium
e.) Yes, because the reaction proceeds backwards until reaching equilibrium
The rate of an enzyme-catalyzed reaction is determine by
a) the overall free energy change of the reaction
b) the equilibrium constant of the reaction
c) the activation energy
d) the number of subunits a single enzyme has
e) all of the above
c) the activation energy
Which of the following amino acids do NOT comprise the catalytic triad of chymotrypsin?
a) histidine
b) glutamic acid
c) serine
d) aspartic acid
b) glutamic acid
All of the following are components of membranes EXCEPT
a) cholesterol
b) triglycerides
c) glycerophospholipids
d) sphingolipids
e) cerebrosides
b) triglycerides
Hexokinase and glucokinase both catalyze the phosphorylation of glucose to form glucose-6-phosphate. The values of K_m for the enzymes of 10 µM and 0.02 M, respectively. If blood glucose is 5 mM under fasting conditions and 20 mM after a high carbohydrate meal.
a. ) hexokinase will function at less than one half V_max after a high carbohydrate meal
b. ) glucokinase will function near its V_max under fasting conditions
c. ) hexokinase will function near its V_max under fasting conditions
d. ) glucokinase will function at less than one-half V_max after a high carbohydrate meal
c.) hexokinase will function near its V_max under fasting conditions
