BANNER ID B 0 0 ______1

INTRODUCTORY BIOCHEMISTRY

BIOL0280 Second Midterm Examination April 3, 2014

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Make sure that your Banner ID is on every page. This is the only way we have of matching you with your exam after grading it. Please work independently. Read each question carefully before answering. Unless otherwise indicated, there is only one correct answer for each multiple-choice question. For multiple choice or matching questions with more than one correct answer, points will be deducted for missing or incorrect responses. Points are indicated by the question within brackets []. There are no calculators or other electronic devices needed or allowed on this exam. All hats must be removed during the exam. Exams will be scanned electronically before being returned.

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1. [2 points] Which of the following reactions can be described as anaplerotic?

A) Oxaloacetate + Acetyl CoA ---> Citrate B) Malate ---> Oxaloacetate C) Pyruvate + CO2 ---> Oxaloacetate D) Both A and C are correct E) All of the above are correct Circle the single correct answer.

2. [2 points] The enzymes that are unique to the glyoxylate cycle include ______.

A) Aconitase B) Malate dehydrogenase C) Fumarase D) Succinate dehydrogenas E) Isocitrate lyase Circle the single correct answer.

3. [4 points] Match the cofactors of the pyruvate dehydrogenase complex in the left column with their corresponding enzyme components and with their roles in the enzymatic steps that are listed in the right column. For each cofactor, indicate ALL correct answers. Each cofactor might have more than one correct answer and the roles and components may apply to more than one cofactor.

Cofactor Enzyme Components and Roles

Coenzyme A ______A) Pyruvate dehydrogenase E1 component B) Dihydrolipoyl dehydrogenase E3 component Thiamine pyrophosphate ______C) Dihyrdolipoyl transacetylase E2 component D) Oxidizes the hyrdoxyethyl group Lipoic acid ______E) Decarboxylates pyruvate F) Accepts the acetyl group from acetyllipoamide NAD+______G) Provides a long flexible arm that conveys intermediates to different enzyme components

I) Oxidizes FADH2

4. [2 points] Which of the following answers complete the sentence correctly? Succinate dehydrogenase

A) is an iron-sulfur protein like aconitase B) contains FAD and NAD+ cofactors like pyruvate dehydrogenase C) is an integral membrane protein unlike the other enzymes of the citric acid cycle D) carries out an oxidative decarboxylation like isocitrate dehydrogenase E) is inhibited by mevalonate Circle the single correct answer.

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5. [2 points] A reaction which involves a substrate-level phosphorylation is:

A) isocitrate ---> α-ketoglutarate B) citrate ---> isocitrate C) succinyl-CoA ---> succinate D) succinate ---> fumarate E) fumarate ---> malate Circle the single correct answer.

6. [4 points] Indicate the order of the following respiratory-chain components from 1-5 with 1 being the first and 5 being the last. Also indicate with an "X" which components are mobile carriers of electrons.

Component Order (1-5) Mobile Carrier ("X")

Cytochrome c ______

NADH:ubiquinone ______oxidoreductase

Cytochrome oxidase ______

Ubiquinone ______

7. [4 points] Explain the difference between oxidative phosphorylation and substrate level phosphorylation in terms of stoichiometry and how ATP is formed.

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8. [2 points] The regulation of the TCA cycle occurs at each of the following enzymes except:

A) citrate synthase B) isocitrate dehydrogenase C) aconitase D) α-ketoglutarate dehydrogenase complex E) pyruvate dehydrogenase complex Circle the single correct answer.

9. [2 points] Coenzyme Q oxidized by complex III can be reduced by:

A) Complex I B) Complex II C) Complex III D) Complex IV E) Glycerol 3-phosphate dehydrogenase Circle all correct answers. More than one answer may be correct.

10. [2 points] Which of the following statements about the proposed mechanism for ATP synthesis by ATP synthase is incorrect?

A) The γ subunit acts as a molecular cam-shaft B) ATP synthase contains active sites that change in their affinity for ATP as protons flow through the complex C) ATP synthase has two active sites per complex D) The energy-requiring step is the release of bound ATP E) Only one of the multiple ATP synthase active sites binds an ATP molecule at a time. Circle the single correct answer.

11. [2 points] The inner mitochondrial membrane contains transporters for which substances?

A) NAD+ B) glycerol 3 phosphate C) ATP D) aspartate E) acetyl CoA Circle all correct answers. More than one answer may be correct.

12. [2 points] Which statement about the cyclic pathway in Photosystem I is correct?

A) It involves NADPH formation B) It uses electrons produced by Photosystem II

C) It generates O2

D) It leads to ATP production via cytochrome b6f complex E) It uses plastaquinone Circle the single correct answer.

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13. [5 points] Assign each function or product from the right column to the appropriate structure or pathway in the left column. Please indicate all correct answers and each statement may have more than one correct answer.

Chlorophyll ______A) O2 generation B) Glyceraldehyde 3-phosphate synthesis Light Harvesting Complex ______C) Light absorption D) NADPH synthesis Photosystem I ______E) Separation of electrons

Photosystem II ______

Calvin cycle ______

14. [2 points] Many antenna chlorophyll molecules absorb light and direct it to the reaction center. The transfer of this absorbed energy is called

A) fluorescence transfer B) redox transfer C) resonance exciton transfer D) electron transfer E) proton transfer Circle the single correct answer.

15. [2 points] What statement is incorrect about RuBisCO?

A) Ribulose 1,5-bisphosphate and carbon dioxide are both substrates B) It contains both a carboxylase and oxygenase activity C) It releases 2 molecules of glyceraldehyde 3-phosphate as a direct product D) It is found in the chloroplast stroma E) It makes up 50% of soluble protein in chloroplasts Circle the single correct answer.

16. [2 points] The process of photorespiration is suppressed in

A) C3 plants B) C4 plants C) CAM plants D) Both B and C are correct E) A, B, and C are correct Circle the single correct answer.

17. [2 points] Which molecule is a product of the reductive phase of the Calvin Cycle (Stage 2)?

A) Ribulose 1,5-bisphosphate B) 3-phosphoglycerate C) Glyceraldehyde 3-phosphate D) ATP E) NADPH Circle the single correct answer.

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18. [4 points] The following is the sequence of reactions in gluconeogenesis from pyruvate to phosphoenolpyruvate:

A B C D pyruvate ------>oxaloacetate ------>malate ------>oxaloacetate ------>phosphoenolpyruvate

Match the letter(s) indicating the reactions of the gluconeogenic pathway above with the following statements. Please indicate all correct answers. Each statement may have more than one correct answer and each reaction might be associated with more than one statements. Letter

Occur in the mitochondria ______

Occur in the cytosol ______

Consumes CO2 ______

Requires ATP ______

19. [4 points] Indicate which of the conditions listed in the right column increase the activity of glycolysis, gluconeogenesis, glycogen synthesis, or glycogen breakdown pathways. Indicate all correct answers for each pathway and each condition may be used for more than one pathway.

Glycolysis ______A) increase in AMP B) increase in F-2,6-BP Gluconeogenesis ______C) increase in insulin D) increase in glucagon Glycogen Synthesis ______E) starvation F) fed state

Glycogen Breakdown ______G) increase in acetyl-CoA

20. [2 points] In the condensation step of the fatty acid synthase enzyme, the addition of two carbon units to the growing fatty chain involves

A) hydrolysis of ATP B) oxidation of NADPH C) reduction of NADP+ D) decarboxylation of malonyl-CoA E) synthesis of ATP Circle the single correct answer.

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21. [5 points] Place the following incomplete list of reactions or relevant locations during β-oxidation of fatty acids in the proper order. Indicate the correct letter of the reaction or location next to the corresponding step.

Reaction or location Order A) acyl CoA import into mitochondrion 1st step) ______

B) thiolysis 2nd step) ______

C) activation of fatty acid with ATP 3rd step) ______

D) hydration 4th step) ______

E) reaction with carnitine 5th step) ______

22. [2 points] Acetyl-CoA carboxylase in animals is regulated by all the following except

A) phosphorylation triggered by glucagon B) allosterically by citrate C) allosterically by palmitoyl-CoA D) allosterically by ATP E) allosterically by malonyl-CoA Circle the single correct answer.

23. [2 points] Indicate whether the statements below are true or false T / F The second bypass reaction of gluconeogenesis is catalyzed by FBPase-1 T / F The second and third bypass reactions of gluconeogenesis produce ATP Circle either T or F for each statement

24. [4 points] If glycogen synthase can add a glucose residue to a growing glycogen molecule only if the glucose chain is at least 8 residues long, how does a new glycogen molecule start? Be sure to describe any enzymes and substrates involved in the process and exactly how the glycogen chain is started.

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25. [2 points] Which of the following reactions are direct sources of glycerol 3-phosphate that is used in triacylglycerol and glycerophospholipid synthesis?

A) Reduction of dihydroxyacetone phosphate B) Oxidation of glyceraldehyde 3-phosphate C) Phosphorylation of glycerol D) Dephosphorylation of 1,3-bisphosphoglycerate E) Reductive phosphorylation of pyruvate Circle all correct answers. More than one answer may be correct.

26. [2 points] Which statement is incorrect about cholesterol biosynthesis?

A) it involves the reduction of β-Hydroxy-β-methylglutaryl-CoA by NADPH to form mevalonate B) the rate of synthesis is regulated by the cellular activity of HMGCoA reductase C) it involves 2 head to tail and one head to head condensations D) it involves the cyclization of squalene to lanosterol by cyclase enzyme Circle the single correct answer.

27. [4 points] Which four of the following compounds can provide the carbon skeletons for biosynthesis of amino acids?

A) 2-Deoxyribose E) Ribose 5-phosphate B) Oxaloacetate F) Glucose 6-phosphate C) α-Ketoglutarate G) 3-Phosphoglycerate D) Succinate H) α-Ketobutyrate Circle all four correct answers.

28. [2 points] Considering all forms of life, which of the following are major excretory forms of the α- amino groups of amino acids?

A) Guanine B) Uracil C) Ammonia D) Uric acid E) Adenine Circle all correct answers. More than one answer may be correct.

29. [2 points] Which of the following statements about the reaction catalyzed by carbamoyl phosphate synthetase I is incorrect

A) it takes place in the mitochondrial matrix B) it involves the cleavage of 2 ATP molecules per urea molecule C) it consumes two molecules of ammonia per urea molecule D) the enzyme that catalyzes it is regulated by N-acetylglutamate E) it involves the phosphorylation of bicarbonate Circle the single correct answer.

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30. [2 points] Fill in the blank in the following sentence. Glycerophospholipids are synthesized by

nucleotide activation either of the ______or the ______. The activated

molecules then condense in a single step to form the final glycerophospholipid product.

31. [4 points] Match the functions from the right column with the appropriate coenzymes, listed in the left column, that are involved in amino acid catabolism.

Pyridoxal phosphate ______A) Transamination reactions

B) One carbon transfer (CH3 only) NAD+ ______C) One carbon transfer (intermediate oxidation states) Tetrahydrofolate ______D) Transfer of electrons

AdoMet ______

32. [2 points] Catabolism of which of the following amino acids requires the direct involvement of O2?

A) Tyrosine B) Isoleucine C) Serine D) Alanine E) Threonine Circle the single correct answer.

33. [2 points] For use during bursts of heavy activity, muscle cells store "high-energy" phosphate as

A) glyceraldehyde 3-phosphate B) 1,3-bisphosphoglycerate C) phosphoenolpyruvate D) phosphocreatine E) pyrophosphate Circle the single correct answer.

34. [2 points] Liver cells have all the necessary enzymes to perform the following conversions except

A) alanine into palmitic acid B) palmitic acid into cholesterol C) glucose into stearic acid D) palmitic acid into glucose E) glucose into serine Circle the single correct answer.

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35. [4 points] Select the statements from the right column that best describe the metabolism of each organ, tissue, or cell in the left column. Please indicate all correct answers.

Brain ______A) releases glycerol and fatty acids into the blood during periods of fasting Muscle ______B) in a normal nutritional state, utilizes glucose as the exclusive fuel Adipose Tissue ______C) synthesizes ketone bodies when the supply of acetyl CoA is high Liver ______D) can release lactate into the blood

E) can store glycogen but cannot release glucose into the blood F) can synthesize fatty acids, triacylglycerols, and VLDL when fuels are abundant

36. [2 points] Fill in the blank in the following statement:

During prolonged fasting, fatty acids in the liver are converted to ______which is/are transported to the ______to be used as fuel.

37. [4 points] Glycogen synthase is activated when cells are treated with insulin. Describe the signaling pathway initiated by insulin, clearly identifying at least four of the kinases, proteins, or lipids that participate and how each is activated.