Carbs II

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emmayarewhy
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237334
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Carbs II
Updated:
2013-09-27 08:06:51
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msbiochem
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msbiochem
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  1. Draw PPP (16)

    Where does it take place?

    WHat is rate limiting step? What inhibits this enzyme?


    Cytosol.


    Glucose 6 DH (G6P --> ribose 5P) kind of; Low NADP+ levels,
  2. Draw different scenarios for ribose-5-P and NADPH balance




  3. 1. What is the first step in aerobic metabolism? Enzyme? Where does it take place? What's so important about it?

    2. Describe the enzyme above and its 3 individual enzymes and the substrates and what it's bound to).
    1. Pyruvate --> AcCoA; PDC; mtiochondria; rate-limiting/irreversible step for aerobic metabolism

    2. PDH = multienzyme complex containing 3 enzymes associated together noncovalently

    • E1 - PDH (thiamine pyrophosate- B1 as cofactor)
    • E2 - dihydrolipoyl transferase (bound to lipoic acid; CoA (B5) as substrate)
    • E3 = dihydrolipoyl dehydrogenase (bound to FAD (B2); substrate is NAD+ (B3)
  4. 1. What is the final common pathway for oxidation of fuel molecules? In what form?

    Draw TCA cycle (8 steps)
    1. TCA cycle in the form of Ac CoA.




  5. 1. What is special about succinate dehydrogenase?  (2)

    2. What is special about a-ketoglutarate DH?

    3. Summary of TCA cycle?

    4. Regulation of TCA?

    5. Function of TCA cycle? (2)
    1. Creates FADH2 instead of NADH, sits on inner mit membrane as part of ETC

    2. Similar to PDH; also affected by vitamin D def (req thiamin (b1), FAD (B2), and CoA (B5).

    3. Acetyl CoA + 3 NAD + 1 FAD + GDP + Pi + H2O --> 2 CO2 + 3 NADH + FADH2 + GTP + 2H+ + CoA


    • 4. Citrate synthase: inhibited by citrate, NADH, succinyl CoA
    • Isocitrate DH: Activated by ADP and Ca2+; inhibited by NADH, ATP

    A-ketoglutarate DH: Activated by Ca2+; inhibietd by NADH

    Malate DH:Inhibited by NADH

    5. To create electron carriers to produce ATP; source of biosynthetic precursors.
  6. Describe shuttle mechanisms to bring NADH into matrix?
    1. Where is each located? *tissue
    2. How many ATP does each NADH ultimately create?
    • 1. Glycerol-3-Phosphate Shuttle (brain/skeletal muscle)

    1.5 ATP/NADH, so 3 ATP from 1 glucose (2 NADH)


    MALATE ASPARTATE SHUTTLE (liver, kidney, heart - more active)

    • 2.5 ATP/NADH --> 5 ATP/glucose.
  7. ETC

    1. How many protons does each complex pump?
    1.5. How many protons/ATP?
    2. What is complex V? Describe each component.

    3. What else can ETC be used for? What is the protien activated by? Who is this important for?
    1. I- 4, III - 2, IV-4. Complex II doesn't pump any protons.

    1.5 - 4 protons/1 ATP. Each NADH from Complex I --> 10/4 = 2.5 ATP. Each FADH2 --> 6/4 = 1.5

    2. F1/F0 ATPase. F0 - pore through which protons can move back into matri (sits on cytoplasmic side) F1 - carries out formation of ATP (points into matrix)

    3. Heat generation NOT ATP through UCP-1 (activated by fatty acids). Important for babies who don't have the shiver reflex and for overweight people potentially.
  8. 1. What does insulin promote? (4)
    2. What does glucagon promote? (4)
    1. Insulin - uptake of glucose into tissues (GLUT 4), glycogen synthesis, glycolysis, TG synthesis in adipose tissue.

    2. Glucagon - glycogenolysis, GNG, release of glucose from liver, lipolysis of TG in adipose tissue.
  9. Draw regulation of glycolysis vs. GNG for the five main enzymes involved.
  10. What is the major enzyme involved in GNG vs. glycolsis regulation? (4) List all points 2, 3, 3, 3

    Describe what happens under fasting conditions and post-prandial conditions
    PFK-1 (fructose <--> F1,6BP)

    1. ATP:AMP ratio (high ATP allosterically inhibits PFK, lowering PFK's affinity for F6P; low ATP:AMP ratio reverses inhibition)

    2. High [H+] - inhibits PFK to prevent lactic acid buildup.

    3. Citrate: high [citrate] inhibits PFK, indicating an abundance of precursor

    4. FRUCTOSE 2,6 BP - potent allosteric activator of pFK, increases PFK affinity for F6P, diminishes ATP inhibition (overrides most other activators)



    1. Glucagon: (1) low blood glucose --> (2) Glucagon released from a-cells (3) binds to glucagon receptor (4) activation of G protein (5) activation of adenylate cyclase --> (6) activation of cAMP (7) activation of PKA (8) P'lases bifunctional enzyme (9) PFK-2 turned off, FBPase2 turned on (10) F2,6BP (PFK activator)--> F6P, no allosteric activator of PFK!!!

    2. Insulin: (1) High blood glucose (2) insulin released from b-cells (3) binds to IR (4) destroys cAMP and releases PP (5) PP dep'lates bifunctional enzyme (6) FBPase 2 turned off, PFK2 turned on (7) PFK2 p'lates F6P --> F2,6BP (8) Activates PFK-1 for glycolysis.
  11. Describe hexokinase vs. glucokinase

    1. Found where? (Tissue)
    2. Km?
    3. Regulation?

    Draw picture of graphs
    1. Hexokinase - muscle/periphery; coordinated with low Km (high affinity) of GLUT 4, allosterically inhibited by product (G6P) to prevent buildup.

    2. Glucokinase (liver, pancrease aka Hexokinase IV) - coordinated with high Km of GLUT 2, not allosterically inhibited by product (G6P) very active at high blood levels.


  12. Pyruvate kinase. Draw picture. What activates it? What inhibits it?
    Activated by insulin (dep'lation) and F1,6 BP. Inhibited by ATP & alanine and glucagon.

  13. PDC:
    In what state is it active? In what state is it deactivated?

    What activates PDC? What inhibits it?
    • PDC is directly activated by Pyruvate and NAD+ and directly inhibited by NADH and Acetyl CoA.
    • PDC = active when dephosphorylated!!!

    PDC Kinase (which turns off PDC) is activated by AcCoA + NADH too and inhibited by ADP + pyruvate.

    PDC phosphatase (which activates PDC) is activated by Ca2+

    Ultimately, Ca2+, Pyruvate, ADP (PDC Kinase), and NAD+ activate PDC.

    PDC is ultimately inhibited by NADH, AcCoA.

  14. What happens to glucagon, insulin, cAMP, Ca2+-calmodulin in the liver during fasting, carb meal, and exercise and stress?

    What happens to insulin, glucagon, epinephrine, AMP, Ca2+ calmodulin, and cAMP in muscle during fasting, carb meal, and exercise?
  15. Draw how glucagon/epinephrine and insulin affect glycogen synthesis vs. breakdown

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