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Chapter 23 Metabolic Pathways for Carbohydrates

Chapter 23 Metabolic Pathways for Carbohydrates. 23.1 Metabolism and Cell Structure 23.2 ATP and Energy 23.3 Important Coenzymes in Metabolic Pathways. Metabolism. Metabolism involves:

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Chapter 23 Metabolic Pathways for Carbohydrates

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  1. Chapter 23 Metabolic Pathways for Carbohydrates 23.1 Metabolism and Cell Structure 23.2 ATP and Energy 23.3 Important Coenzymes in Metabolic Pathways

  2. Metabolism Metabolism involves: • Catabolic reactions that break down large, complex molecules to provide energy and smaller molecules. • Anabolic reactions that use ATP energy to build larger molecules.

  3. Stages of Metabolism Catabolic reactions are organized as stages: • In Stage 1, digestion breaks down large molecules into smaller ones that enter the bloodstream. • In Stage 2, molecules in the cells are broken down to two- and three-carbon compounds. • In Stage 3, compounds are oxidized in the citric acid cycle to provide energy.

  4. Stages of Metabolism

  5. Cell Structure • Metabolic reaction occur in specific sites within cells.

  6. Cell Components and Function

  7. ATP and Energy • In cells, energy is stored in adenosine triphosphate (ATP).

  8. Hydrolysis of ATP • The hydrolysis of ATP to ADP releases 7.3 kcal (31 kJ/mole). ATP ADP + Pi + 7.3 kcal (31 kJ/mole) • The hydrolysis of ADP to AMP releases 7.3 kcal (31 kJ/mole). ADP AMP + Pi + 7.3 kcal (31 kJ/mole)

  9. Hydrolysis of ATP to ADP and ADP to AMP

  10. ATP and Muscle Contraction • Muscle fibers contains filaments of actin and myosin. • When a nerve impulse increases Ca2+, the filaments slide closer together to contract muscle. • The hydrolysis of ATP in muscle provides the energy for contraction. • As Ca2+ and ATP decrease, the filaments return to the relaxed position.

  11. ATP and Muscle Contraction

  12. Coenzyme NAD+ • In cells, the oxidation of compounds provides 2H as 2H+ and 2e- that reduce coenzymes. • NAD+ (nicotinamide adenine dinucleotide) participates in reactions that produce a carbon-oxygen double bond (C=O). Oxidation O || CH3—CH2—OH CH3—C—H + 2H+ + 2e- Reduction NAD+ + 2H+ + 2e- NADH + H+

  13. Structure of Coenzyme NAD+ • NAD+ (nicotinamide adenine dinucleotide) contains ADP, ribose, and nicotinamide. • NAD+ reduces to NADH when the nicotinamide group accepts H+ and 2e-.

  14. Coenzyme FAD • FAD participates in reactions that produce a carbon-carbon double bond (C=C). Oxidation —CH2—CH2— —CH=CH— + 2H+ + 2e- Reduction FAD + 2H+ + 2e- FADH2

  15. Structure of Coenzyme FAD • FAD(flavin adenine dinucleotide) contains ADP and riboflavin (vitamin B2). • FADreduces to FADH2 when flavin accepts 2H+ and 2e-.

  16. Coenzyme A • CoA activates acyl groups such as the two-carbon acetyl group for transfer. O O || || CH3—C— + HS—CoA CH3—C—S—CoA

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