Question

41. Find the mismatched pair:

A) Entropy (ΔS)—measurement of disorder in a thermodynamic system

B) First Law of Thermodynamics—Energy in a system is not created nor destroyed, only transformed

C) Second Law of Thermodynamics—The entropy of a perfect crystal at 0 K is exactly equal to zero.

D) Standard free energy (Go )—The useful energy in a system

E) ΔG < 0—Energetically favorable (spontaneous) reaction

42. Which of the following reactions is unfavorable?

A) NaCl dissolving in water (ΔG < 0)

B) Formation of peptide bonds during protein synthesis (ΔGo values vary from +10 to +20 kJ/mol)

C) Hydrolysis of ATP to ADP + ℗ (ΔGo ʹ = –30.5 kJ/mol)

D) Oxidation of a 16-carbon (C16) fatty acid releases enough energy to synthesize 130 ATPs

E) Oxidation of one molecule of glucose (C6) yields up to 8 ATPs in eukaryotic cells

43. In metabolic reactions the equilibrium constant (K) is modified by enzymes.

A) True

B) False

44. Which of the following is incorrect regarding Gibbs free energy?

A) ΔG = ΔGo + RT ln [!] [!] (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 = [!] [!]

C) ΔG = ΔH – TΔS

D) ΔGo ʹ = ΔGo at pH 7

E) None of the above

45. 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

46. 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?

47. 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

48. 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)

Answer 1

1) A) Entropy (ΔS)—measurement of disorder in a thermodynamic system is a correct statement

B) First Law of Thermodynamics—Energy in a system is not created nor destroyed, only transformed is also correct statement

C) Second Law of Thermodynamics—The entropy of a perfect crystal at 0 K is exactly equal to zero is not correct statement because the statement is about third law of thermodynamics.

Second law of thermodynamics - It is about entropy of system always increases

D) Standard free energy (Go )—The useful energy in a system is a correct statement

E) ΔG < 0—Energetically favorable (spontaneous) reaction is also correct statement.

2) A) NaCl dissolving in water (ΔG < 0) is favorable energetically and spontaneous reaction

B) Formation of peptide bonds during protein synthesis (ΔGo values vary from +10 to +20 kJ/mol) is unfavourable reaction because ( ΔGo>0)

C) Hydrolysis of ATP to ADP + ℗ (ΔGo ʹ = –30.5 kJ/mol) not correct option because favorable energetically and spontaneous reaction ( ΔGo< 0)

D) Oxidation of a 16-carbon (C16) fatty acid releases enough energy to synthesize 130 ATPs is unfavourable reaction because ( ΔGo>0) because we can see in the above example ATP ----> ADP + P ΔGo ʹ = –30.5 kJ/mol then formation of ATP molecules is reverse of the reaction ΔGo ʹ = +30.5 kJ/mol

E) Oxidation of one molecule of glucose (C6) yields up to 8 ATPs in eukaryotic cells is unfavourable reaction because ( ΔGo>0) because we can see in the above example ATP ----> ADP + P ΔGo ʹ = –30.5 kJ/mol then formation of ATP molecules is reverse of the reaction ΔGo ʹ = +30.5 kJ/mol

3) In metabolic reactions the equilibrium constant (K) is modified by enzymes is a False statement because the equilibrium constant (K) is not modified by the enzymes used in the metabolic reactions. Enzymes are used to accelerate the metabolic reactions but they do not involve. They act as biocatalyst without interfering in the reaction.

4) Gibbs free energy can be calculated by

A) ΔG = ΔGo + RT ln ([x]/ [y]) (kJ/mol) for the reaction Y --> X; R is the gas constant and T is temperature in K is a correct formula

B) ΔGo = –1.42 log K, where K =([x]/ [y]) is also correct formula by converting into logarithmically

C) ΔG = ΔH – TΔS is also correct formula for a thermodynamic system

D) ΔGo ʹ = ΔGo at pH 7 is also correct formula at pH = 7

E) None of the above

5) Enzymes are true catalysts because

A) they decrease the energy of activation required for the reactions they participate in is a true statement. They speed up the reaction by straining itself (changing its shape) when substrate binds which is known as induced fit theory.

B) they are required in small amounts is a correct statement as they do not alter in reaction small amount is enough

C) they are not consumed in the reaction is a correct statement they just speed up the reaction but do not involve

D) they increase reaction rates without altering the chemical equilibrium between reactants and products is a correct statement and enzymes neither consumed nor altered when reaction rate is increased.

E) All of the above

All of the above is a correct answer

6) enzymes is

A) “Not all proteins are enzymes, but all enzymes are proteins.” is wrong axiom because some of the enzymes may require cofactors like Mg⁺² or coenzymes like FAD for the catalytic action. Some RNA's have catalytic activities like ribozymes which are not protein in nature.

B) “Not all proteins are enzymes and not all enzymes are proteins.” is correct axiom as discussed above

C) “Not all enzymes are proteins; some enzymes depend on RNA for their catalytic activity.” is correct axiom as discussed above

D) Can you repeat the question?

7) limitations of protein enzymes - Usually protein enzymatic activity are influenced by

A) Enzyme concentration b) substrate concentration c) inhibitors d) temperature e) pH

A) They are active within a certain range of temperature is correct statement. Optimum temperature is required for the better enzymatic activity

B) They are limited to a pH range is also correct statement. Optimum pH is  required for the better enzymatic activity

C) They may have specific requirements (coenzymes or cofactors) is also correct statement they may required for the better enzymatic activity. Examples of coenzymes are FAD/NAD etc and cofactors - Zn⁺², Mg⁺²

D) All of the above is correct option

E) None of the above

8) 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) - 3 -  because less steric hindrance ( less steric and electronic effects)

than the alcohol derivatives and alkyl derivatives.

B) CH4, CH3CH3 (methane, ethane) - 1 - because there are no oxygen atoms.

C) HCOOH, CH3COOH (formic acid, acetic acid) - 4 -  because of more oxygen atoms and less steric effects when compared to other 3 molecules.

D) CH3OH, CH3CH2OH (methanol) - 2 because of more steric hindrance

E) CO2, H3C–O–CO–O–CO–O–CH3 (carbon dioxide, dimethylpyrocarbonate) - 5 because of more oxygen atoms and less steric effects when compared to other 4 molecules.