example exam questions exam 2 (Q1-12)
Electronegativity is defined as the measure of the tendency of an atom to attract a bonding pair of electrons. Oxygen is a powerful oxidant because it is more electronegative than C and H. Arrange the following pairs of molecules in order with respect to their relative levels of oxidation (assign 5 to the most oxidized and 1 to the most reduced). a) HCHO, CH3CHO (formaldehyde, acetaldehyde) b) CH4, CH3CH3 (methane, ethane) c) HCOOH, CH3COOH (formic acid, acetic acid) d) CH3OH, CH3CH2OH (methanol) e) CO2, H3C-O-CO-O-CO-O-CH3 (carbon dioxide, dimethylpyrocarbonate)
5->1 e,c,a,d,b e=5,c=4,a=3,d=2,b=1
Which of the following axioms regarding enzymes is not correct? a) "Not all proteins are enzymes, but all enzymes are proteins." b) "Not all proteins are enzymes and not all enzymes are proteins." c) "Not all enzymes are proteins; some enzymes depend on RNA for their catalytic activity." d) Can you repeat the question?
A is incorrect
The biosynthetic pathway for the two amino acids E and H is 11. shown schematically in the figure on the right. You are able to show that E inhibits enzyme V, and H inhibits enzyme X. Enzyme T is most likely to be subject to feedback inhibition by ____ alone. A--T---> B---U---> C **(*---v--->D----w---E) (*----x---F----y--->G---z--->H) H inhibits x and E inhibits v. a) H b) B c) C d) E
C?
What are the limitations of protein enzymes? a) They are active within a certain range of temperature. b) They are limited to a pH range. c) They may have specific requirements (coenzymes or cofactors) d) All of the above e) None of the above
D all the examples are limitations of protein enzymes
Find the mismatched pair: a) Entropy (ΔS)—measurement of disorder in a thermodynamic system b) ΔG < 0—Energetically favorable (spontaneous) reaction c) First Law of Thermodynamics—Energy in a system is not created nor destroyed, only transformed d) Second Law of Thermodynamics—The entropy of a perfect crystal at 0 K is exactly equal to zero. e) Standard free energy (Go)—The useful energy in a system
D is wrong. The second law of thermodynamics is that entropy of a system always increases. The third law of thermodynamics is that a perfect crystal with zero temperature has an entropy of zero.
Find the mismatched pair: a) Entropy (ΔS)—measurement of disorder in a thermodynamic system b) ΔG < 0—Energetically favorable (spontaneous) reaction c) First Law of Thermodynamics—Energy in a system is not created nor destroyed, only transformed d) Second Law of Thermodynamics—The entropy of a perfect crystal at 0 K is exactly equal to zero. e) Standard free energy (Go)—The useful energy in a system
D is wrong. The second law of thermodynamics is that entropy of a system always increases. The third law of thermodynamics is that an object with zero temperature has an entropy of zero.
In metabolic reactions the equilibrium constant (K) is modified by enzyme? a) True a) False
False, No the constant is not modified by the enzyme
If proteins A and B have complementary surfaces, they may interact to form the dimeric complex AB. Which of the following is the correct way to calculate the equilibrium constant, K, for the association between A and B? a) K = [A][B]/[AB] b) K = [AB]/[A][B] c) K = kon/koff = [AB]/[A][B] d) Both b) and c) are correct e) Neither a), b) nor c) are correct
K = equilibrium constant [products]/[reactants] B and C
Which of the following is incorrect regarding Gibbs free energy? a) ΔG = ΔGo + RT ln (x/y) (kJ/mol) for the reaction Y à X; R is the gas constant and T is temperature in K b) ΔGo = -1.42 log K, where K = (x/y) c) ΔG = ΔH - TΔS d) ΔGo ʹ = ΔGo at pH 7 e) None of the above
all are correct examples of how to calculate delta G
Enzymes are true catalysts because a) they decrease the energy of activation required for the reactions they participate in. b) they are required in small amounts. c) they are not consumed in the reaction. d) they increase reaction rates without altering the chemical equilibrium between reactants and products e) All of the above
all of the above is true