1. Describe the role of coupled reactions in metabolism, give an example of a coupled reaction in one of the biochemical pathways we have covered AND identify the high energy compound in the reaction. (Sound Familiar)? (9 pts)

• In coupled reactions, one exergonic reaction drives an endergonic reaction (3 pt).
• An example is provided by the two half reactions below (3 pt):

Reaction 1: F6P + Pi -> FBP D G >0

Reaction 2: ATP + H2O -> ADP + Pi D G <0

Sum D G <0

1. Identify Enzyme Inhibitors A and B as competitive, uncompetitive or mixed inhibitors: (6pts)

Inhibitor A is Competitive (Apparent Km increases; Vmax does not change





 

 

 

Inhibitor B is Mixed (Apparent Km and Vmax change)



 



 

 

2. What role does compartmentalization play in metabolism? AND Name or describe a transporter involved in carbohydrate or lipid metabolism.

4. Identify each of the following pathways or processes and indicate if the process occurs in the cytoplasm or mitochondrion. (10 pts)

Process	Name of Process/ Cellular Compartment
Synthesizes ATP from ADP. Is driven by the separation of charge across the inner mitochondrial membrane.	Name: Oxidative Phosphorylation Compartment: Mitochondrion
Transfers electrons in a series of redox reactions that produces a separation of charge across the inner mitochondrial membrane. Ultimately transfers electrons to O2 which is then reduced to H2O.	Name: Electron Transport Chain Compartment: Mitochondrion
Chops 2 carbons off a fatty acid each time it goes around the cycle making the process look like a spiral. Each 2 carbon unit becomes acetyl CoA.	Name: Fatty Acid Oxidation Compartment: Mitochondrion
Accepts 2 carbons from acetyl CoA which combine with oxaloacetic acid to form citric acid. Generates CO2 and reduced coenzymes (NADH and FADH2). (Coenzymes carry electrons to the electron transport chain). Regenerates oxaloacetic acid.	Name: Citric Acid Cycle; TCA or Kreb's cycle Compartment: Mitochondrion
Converts 1 mole of glucose to 2 moles of pyruvate	Name: Glycolysis Compartment: Cytosol

5. BRIEFLY describe (8 pts):

• The reaction catalyzed by the pyruvate dehydrogenase complex in carbohydrate metabolism:

Pyruvate + NAD⁺ + CoA ® CO₂ + NADH + AcetylCoA

• One advantage of a multienzyme complex
• Reactions happen faster because of proximity of reactants
• Fewer side reactions
• Coordinated control
• With reference to the picture below, explain how pyruvate dehydrogenase is regulated. (Graphs of enzyme activity would be cool)!

• What effect would increasing expression of the PDH kinase gene have on carbohydrate metabolism? (In other words, if concentrations of PDH kinase protein increased, what effect would this have on carbohydrate metabolism?)

6. The O₂ consumption curve of a dilute, well buffered suspension of mitochondria containing plenty of ADP and Pi looks like:

7. Referring to the figure in #6 above, sketch the curves you would predict when (10 pts):

i. Rotenone is added at T₁; and succinate is added at T₂

ii. CN^- is added at T₁; and succinate is added at T₂

8. (12 pts) Draw graphs to illustrate allosteric effects of fructose-2,6-bisphosphate (F2,6P) on

a. Phosphofructokinase (F6P ® F1,6P)

2. Fructobisphosphatase (F1,6P ® F6P)
3. What role does F2,6P play in regulating glycolysis and gluconeogenesis? (use back of page)

9. Name or draw the reactancts and products or name the four enzymes that catalyze the reactions that bypass the three exergonic steps of glycolysis: (8pts)

10. Fatty acid oxidation occurs in four reactions. In the Citric Acid Cycle below, identify three consecutive reactions that are similar to those seen in fatty acid oxidation (6 pts)

9. Complete the following table with reference to the Citric Acid Cycle above (8 pts):

Enzyme	Classification	Is Reaction Irreversible?
Citrate Synthase	Transacetase or Transferase	YES
Aconitase	Hydratase	NO
Isocitrate Dehydrogenase	Oxidoreductase	YES
a -Ketoglutarate Dehydrogenase Complex	Oxidoreductase	YES
Succinyl CoA Synthase	Ligase	NO
Succinate Dehyrogenase	Oxidoreductase	NO
Fumarase	Hydratase	NO
Malate Dehydrogenase	Oxidoreductase	NO

10. Briefly answer the following (4 pts):

1. Name at least one role of the pentose phosphate pathway in carbohydrate metabolism.

1. Synthesis of Ribose-5-phosphate for nucleotide biosynthesis
2. Synthesis of NADPH (used for reductive biosynthesis and regeneration of reduced glutathione

b. What enzyme catalyzes the rate limiting step in the pentose phosphate pathway?

9. Olean (Olestra) is a fat free "fat" used for producing fat free foods. Olean is a sugar (maybe fructose or glucose) with fatty acids esterified onto each of its numerous OH groups. Olean is "fat free" because none of the fatty acids are absorbed from the intestine into the blood. For this reason, diarrhea and gastric bloating can result if you eat too much of those fat free chips. Why are the fatty acids in Olean not absorbed? (4 pts)