Energy & Enzymes

Energy & Enzymes

1. All of the following are true about enzymes except:
a. They can lower the activation energy for a reaction
b. They speed up chemical reactions
c. They lower the delta G for a reaction
d. They are used up in chemical reactions
e. One enzyme catalyzes many different chemical reactions

2. Which of the following reactions cannot occur spontaneously?
a. Glucose 6 phosphate -> fructose 6 phosphate; delta G=+0.4 kcal/mol
b. ATP -> ADP + P; delta G=-7.3 kcal/mol
c. Pyruvate -> lactose; delta G=-6.0 kcal/mol
d. ADP -> AMP + P; delta G=-7.3 cal/mol
e. None of the above

3. The role of NAD+ in the following reaction is: Lactate + NAD+ -> pyruvate + NADH
a. Enzyme
b. Energy source
c. Substrate
d. Coenzyme
e. None of the above

4. Catalase is composed of a protein and a heme. The heme consists of a ringed protoporphyrin and an iron atom. Which of the components is the cofactor?
a. Protein
b. Heme
c. Protoporphyrin
d. Iron
e. None of the above

5. The enzyme threonine deaminase removes -NH2 from threonine in the first reaction in the pathway: Threonine->Intermediate 1->Intermediate 2->Intermediate 3->Intermediate 4->Isoleucine. Isoleucine inhibits this enzyme by:
a. Competitive inhibition
b. Denaturing the enzyme
c. Feedback inhibition
d. Allosteric activation
e. Reversing the reaction

6. Lactate dehydrogenase (LDH) in muscle cells consists of four M subunits and LDH in heart cells consists of four H units. These forms of LDH are called:
a. Isozymes
b. Proenzymes
c. Allosteric activators
d. Enzymes
e. None of the above

7. Which of the following types of inhibition can be reversed by the presence of excess substrate?
a. Noncompetitive inhibition
b. Competitive inhibition
c. Irreversible inhibitors
d. Increased temperature
e. All of the above

8. One abnormal enzyme found in cancer cells is serine kinase which phosphorylates the amino acid tyrosine instead of serine. Which of the following is the best explanation for the resultant increase in cell growth?
a. Competitive inhibition of enzymes containing serine
b. Allosteric inhibition of enzymes containing tyrosine
c. Activation of enzymes containing tyrosine
d. Reversing biochemical reactions
e. A multienzyme complex

9. Copper is used in lakes to kill algae. The algicidal action of copper is most likely due to:
a. Competitive inhibition
b. Denaturing the enzyme
c. Allosteric inhibition
d. Allosteric activation
e. Reversing the reaction

10. Assume _Saccharomyces cerevisiae_ is grown in a nutrient medium containing the radioisotope S-35. After 48 hrs incubation, the S-35 would most likely be found in the yeastıs:
a. Carbohydrates
b. Nucleic acids
c. Water
d. Lipids
e. Proteins

11. Assume _Saccharomyces cerevisiae_ is grown in a nutrient medium containing the radioisotope P-32. After 48 hr incubation, the P-32 would most likely be found in the yeastıs:
a. Plasma membrane
b. Cell wall
c. Water
d. Protein
e. None of the above

12. Assume a human cell is grown in a nutrient medium containing the radioisotope N-16. After 48 hr incubation, the N-16 would most likely be found in the cellıs:
a. Carbohydrates
b. Lipids
c. Water
d. Proteins
e. None of the above

13. Which organism is not correctly matched to its energy source?
a. Photoheterotroph-light
b. Photoautotroph-carbon dioxide
c. Chemoautotroph-Fe (2+)
d. Chemoheterotroph-glucose
e. Chemoautotroph-ammonia

14. All of the following are true about substrate-level phosphorylation except:
a. It involves the direct transfer of a high-energy phosphate group from an intermediate metabolic compound to ADP
b. No final electron acceptor is required
c. It occurs in glycolysis
d. The oxidation of intermediate metabolic compounds releases energy that is used to generate ATP
e. All of the above are true

15. Which one of the following is an enzyme?
a. Coenzyme Q
b. Vitamin A
c. NAD+
d. Beta-galactosidase
e. All of the above are enzymes