Part I: [42 pts]: For multiple choice, choose the one BEST answer. Circle its letter. Read each question and all 5 choices carefully because more than one answer might seem correct at first glance. 2 points each

1. Glyceraldehyde is
a. an aldose
b. has one asymmetrical carbon with two stereoisomers
c. has one symmetrical carbon with two stereoisomers
d. a and b
e. a and c

2. Aerobic organisms often derive free energy from oxidation of fuel molecules such as fatty acids and glucose. Which of the following is FALSE with respect to oxidation?
a. oxidation is the transfer of electrons, often with hydrogen atoms attached, to electron carrier proteins
b. NAD⁺ is an important electron acceptor which is capable of accepting 2 electrons and a hydrogen ion
c. FAD accepts 2 electrons, a hydrogen atom, and an H⁺
d. oxygen is the final electron acceptor in oxidation of fuel molecules by aerobic organisms
e. all of the above are TRUE

3. A non-spontaneous reaction can be driven by a spontaneous reaction if they are coupled via
a. activated protein conformation
b. ionic gradient across a membrane
c. shared chemical intermediate
d. a and b
e. all of the above

4. Which of the following is NOT true of metabolism?
a. it involves conversion of energy from one form to another
b. there are a large number of different categories of reactions
c. many different reactions occur
d. metabolic pathways and reactions are regulated in common
e. all of the above are true

5. ATP is known as the "universal" donor of free energy. Why?
a. ATP has two energy rich phosphoanhydride bonds; energy is liberated when one or both of these bonds is broken
b. ATP, ADP, and AMP are easily interconvertible, and the turnover rate is very high.
c. ATP has phosphoryl transfer potential that is intermediate among the biologically important phosphorylated molecules, making it an efficient carrier of phosphoryl groups.
d. All of the above are valid reasons why ATP is the universal energy currency.
e. All of the above are false; ATP is used because it easily binds carrier proteins for transport to muscles (or wherever it is needed)

6. Given ......................................... A --> B + C DG^o’ = +5 kcal/mol
Which of the following B --> D DG^o’ = - 8 kcal/mol
are true? A --> C + D DG^o’ = -3 kcal/mol
a. A cannot be spontaneously converted into B because D G is positive
b. in this example, B is the shared intermediate which couples the two reactions
c. conversion of A into C + D has a negative DG, so it can occur spontaneously under standard conditions
d. a and b
e. all of the above

7. In the Krebs cycle
a. there are four oxidative reactions by which four pairs of hydrogen atoms are transferred to NAD⁺ and FAD.
b. two water molecules are consumed in each turn
c. the NADH and FADH₂ formed by the cycle are ultimately oxidized by the electron transport chain
d. the Krebs cycle is strictly aerobic, whereas glycolysis can occur under anaerobic conditions as well
e. all of the above

8. Which of the following are disaccharides?
a. sucrose
b. maltose
c. lactose
d. a and b
e. all of the above

9. The anomeric carbon:
a. its configuration determines whether the sugar is a or b
b. its configuration determines whether the sugar is l- or d-
c. is a carbon outside the ring
d. can only be identified in the linear form of the sugar
e. is always C-1

10.Two molecules which are mirror -images of each other are called, specifically
a. stereoisomers
b. enantiomers
c. epimers
d. diastereoisomers
e. all of the above

11. The hydrolysis of glucose to CO₂ + H₂O is completed by the oxidation of acetyl CoA to CO₂ in the
a. Krebs cycle
b. TCA cycle
c. citric acid cycle
d. a and b
e. all of the above

12. Carbohydrates
a. are used as fuel
b. are used to store energy
c. link to polypeptides and lipids in membranes
d. are metabolic intermediates
e. all of the above

13. b-1,4 linkages between glucose molecules in a homopolymer of glucose
a. are very unstable exist rarely
b. make the polymer very water soluble
c. can be hydrolyzed by enzymes found rarely in the animal kingdom
d. are found primarily in microorganisms
e. are typical of animal glucose homopolymers

14. The major source of ATP in aerobic organisms is
a. TCA cycle
b. glycolysis
c. oxidative phosphorylation
d. creatine
e. all of the above

15. Under physiological conditions, the reactions of glycolysis
a. are readily reversible - except those catalyzed by hexokinase, phosphofructokinase, and pyruvate kinase
b. convert glucose into pyruvate
c. produce more ATP for the body than any other enzymatic pathway
d. a and b
e. all of the above

16. Which of the following is an isomerization reaction?
a. ketose <==> aldose
b. ATP <==> ADP + P_i
c. C=O <==> H-C-OH
d. removal of a water molecule
e. furanose <==> pyranose

17.Which of the following is true with respect to the many configurations of a six carbon sugar?
a. both d and l configurations exist only for sugars with >1 asymmetric carbon
b. an additional asymmetric center is created when glucose cyclizes
c. the predominant form of glucose in solution is a mixture of cyclized ring structures
d. d-glucose and d-mannose are epimers of one another, but they are not diastereoisomers
e. all hexoses readily form pyranose and furanose ring structures

18. Enzyme(s) which regulate glycolysis include
a. hexokinase
b. phosphofructokinase
c. pyruvate kinase
d. a and b
e. all of the above

19. The citric acid cycle begins when two molecules are linked. Name these two molecules and indicate their respective sizes

20. In eukaryotes, the TCA cycle occurs in which cellular compartment?

21. In eukaryotes, glycolysis occurs in which cellular compartment?

Part II. [30 pts] Short answer. Choose 5 (omit 2). 6 points each

1. A non-spontaneous reaction can be driven by a spontaneous reaction. Choose two mechanisms by which such reactions can be coupled. For each, briefly explain the mechanism; give one specific example.

2. cont... Choose two more [different] mechanisms.

3,4. You may choose 3 or 6 of the following ... define or diagram the action of:

a. aldol cleavage        b. phosphoryl transfer              c. dehydrogenase (dehydration)

d. phosphoryl shift      e. isomerase                            f. kinase g. mutase

5. One of the Tables in your text lists the "typical concentrations of glycolytic intermediates in erythrocytes". How is this information important to our understanding of the rates of reaction in the glycolysis pathway? For example, what would happen if one (or a few) of these concentrations dropped or rose significantly? (it is not necessary to give a specific example, just discuss the basic principles).

6. Diagram and explain the regulation of phosphofructokinase.

7. Describe, in brief, the steps of glycolysis. It is sufficient to show (a) size of sugar and (b) position of phosphate(s) at each step.

Part III. [28 pts] Shorter answer. 4 points each

1. Other than coupling two reactions (see above), under what circumstances can a thermodynamically unfavorable reaction (DG>0) occur? Give an example.

2. Draw d-glucose and l-glucose

3. Identify the following molecules: what are they made of, where are they found, what are they for?

a. glycogen

b. chitin

4. ... cont.... c. sucrose

d. cellulose

5. Regulated enzymes are usually those that catalyze irreversible (or virtually irreversible) reactions. Explain why this should be so.

6. a. What is the difference between an O-glycosidic bond and an N-glycosidic bond?

b. explain how bonds between sugars are named. (a diagram of an example would be sufficient)

7. The citric acid cycle is considered to be aerobic even though no O₂ is actually used or involved. Explain.

EXTRA CREDIT: Write you own question and answer it. HINT: this is you opportunity to show what you know. Do not ask yourself a question if you aren't sure of the answer. Ask the question you were sure would be on the exam, so you studied the material, and then somehow it was left off! Your score will depend on the quality of the question as well as the answer - up to a possible maximum of 5 pts.