Announcements

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Announcements

• Reading for today on glycolysis pp. 221-234
• Homework due today Problems 8-5, 8-7
• In both problems, use the favorable free energy
  change of ATP hydrolysis to drive the unfavorable
  transport of solute up its concentration gradient
  on a per mole basis.
• Reading for Wednesday, Feb. 21 on fermentation
  and TCA cycle 236-241, 248-258
• Reading for Friday, Feb. 23 on integration of
  metabolism 258-262
• Reading for Monday, Feb. 26 on respiration
  265-271
• Homework due Monday, Feb. 26 Problem 9-5
• Convert all concentrations to M, and your answer
  will be in M.
• Dont worry about H use equations as given
  in problem.
• Determine glucose at equilibrium (?G 0)
  then a concentration greater than this will favor
  production of G6P.
• Wednesday, Feb. 28 on respiration 271-283
• Friday Exam 2 on Days 12-22, 99 points, 33 m/c
  questions.
• Note Exam 3 will be worth 81 points.

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Outline/Learning Objectives

• CHO metabolism
• Metabolic reactions and ATP
• Oxidation-reduction reactions
• Glycolysis

• After reading the text, attending lecture, and
  reviewing lecture notes, you should be able to
• Describe the roles of ATP/ADP and NAD/NADH in
  biological reactions.
• Summarize the purpose and place, reactants and
  products, critical enzymes, and net yield of
  glycolysis.
• Calculate free energy changes associated with
  glycolysis.
• Summarize the products, control steps, etc. of
  glycolysis.

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Catabolic and Anabolic Metabolic Pathways

• Catabolic (degradative)
• Glycolysis, fermentation
• TCA cycle, electron transport, oxidative
  phosphorylation
• Glycogenolysis
• Fatty acid oxidation
• Amino acid degradation

• Anabolic (synthetic)
• Gluconeogenesis
• Glycogen synthesis
• Fatty acid synthesis
• Amino acid synthesis

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ATP is an energy intermediate
Donates Phosphate Hydrolysis is exergonic
Accepts Phosphate Synthesis is endergonic
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Oxidation and Reduction

• Oxidation gives up e-
• Dehydrogenation gives up H
• Reduction accepts e-
• Hydrogenation accepts H
• Redox reactions
• Usually involve 2 e-, 2 H in the cell
• Catalyzed by dehydrogenases

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NAD accepts, NADH donates e-
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NAD/NADH is an intermediate e- acceptor/donor

• Its redox reaction is coupled to another redox
  reaction in metabolic pathways
• NADH H ? NAD 2e- 2H
• Acetaldehyde 2e- 2H ? ethanol
• Acetaldehyde NADH H ? ethanol NAD
• This fermentation reaction is catalyzed by
  alcohol dehydrogenase.

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Final e- Acceptors

• Glycolysis, fermentation (NAD )
• No net oxidation of glucose
• Aerobic respiration O2
• Complete oxidation of glucose using O2 as final
  e- acceptor ½ O2 2 H 2 e- ? H2O
• Anaerobic respiration S, H, Fe3
• Complete oxidation of glucose using something
  other than O2 as final e- acceptor.
• Glycolysis is the central catabolic pathway and
  first part of aerobic respiration

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Oxidation of Glucose

• C6H12O6 6 O2 ? 6 CO2 6 H2O
• ?Go -686 kcal/mol
• In bomb calorimeter, the large EA of this rxn is
  overcome by heat of fire.
• In the cell, a series of reactions with small EA
  is overcome by body temperature and enzymes.
• Purpose convert chemical bond energy of glucose
  to chemical bond energy in ATP

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Glycolysis Problems

• 2-88
• 2-89
• 2-90
• 2-93

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Energetics of Glycolysis
1 M Conc., pH7
cellular Conc., pH7
STEP REACTION ?Go ?G
1 GLC ATP ? G6P ADP H -4.0 -8.0
2 G6P ? F6P 0.4 -0.6
3 F6P ATP ? F1,6BP ADP H -3.4 -5.3
4 F1,6BP ? DHAP G3P 5.7 -0.3
5 DHAP ? G3P 1.8 0.6
6 G3P Pi NAD ? 1,3BPG NADH H 1.5 -0.4
7 1,3BPG ADP ? 3PG ATP -4.5 0.3
8 3PG ? 2PG 1.1 0.2
9 2PG ? PEP H2O 0.4 -0.8
10 PEP ADP H ? PYR ATP -7.5 -4.0
The table above shows free energy change values
in kcal/mol for the concentrations of
intermediates in red blood cells. The overall ?G
from glucose to pyruvate is about -20 kcal/mol.
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Glycolysis Summary

• Cytoplasmic
• Catabolism of
• carbohydrates ? G6P, F6P
• fats glycerol ? DHAP
• some amino acids ? pyruvate
• Cost 2 ATP, Gain 4 ATP, Net Gain 2 ATP
• Reduced Coenzymes 2 NADH H
• End product pyruvate (CH3COCOO-)
• Control steps irreversible reactions 1, 3, and 10