06 Glucose Alternatives.pptx

Metabolism Overview

• Metabolism of Other Stuff

  • Discussion of metabolic processes not solely focused on glucose.

Glucose Alternatives

• Cellular Respiration

  • Can utilize not just carbohydrates but also proteins and fats.

  • Different enzymes are responsible for breaking down these molecules for entry into the metabolic pathway.

Ultimate Metabolic Products

• Macromolecule Digestion Products

  • Nucleic acids → Nucleotides

  • Proteins → Amino Acids

  • Polysaccharides → Simple Sugars

  • Lipids/Fats → Fatty Acids

  • Waste Products: NH3 (ammonia), CO2 (carbon dioxide), H2O (water)

• Key Metabolic Pathways

  • Krebs Cycle utilizes Acetyl-CoA and Pyruvate.

  • Glycolysis and Gluconeogenesis processes take place, as well as β-oxidation and deamination.

Protein Metabolism

• Amino Acid Utilization

  • Proteins are generally broken into amino acids for further synthesis of new proteins.

  • Some amino acids undergo metabolism which starts with deamination, converting the amino group into ammonia for excretion.

  • The remaining parts are repurposed for cellular respiration.

• Amino Acid Transformations

  • Example of conversions:

    • Leucine (6 carbons) → 3 Acetyl-CoA molecules

    • Alanine (3 carbons) → converted to Pyruvate

    • Proline (5 carbons) → converted to α-ketoglutarate

Fat Metabolism

• Fat Breakdown Process

  • Fats are split into glycerol and fatty acids:

    • Glycerol (3 carbons):

      • Can be converted into glucose through gluconeogenesis, though rarely.

      • More commonly changed into DHAP and then G3P with an ATP cost of 1.

    • Fatty Acids (multiple carbons):

      • Transported to the mitochondrial matrix for β-oxidation.

      • Enzymatic degradation removes 2-carbon units from the fatty acids, converting these units to Acetyl-CoA.

Example of Fatty Acid Metabolism

• Metabolism of Lauric Acid (12 carbons)

  • Total fatty acid breakdown:

    • Cuts: 5 (each removing a 2-carbon unit)

    • Resulting Acetyl-CoA: 6

    • ATP generated from metabolism:

      • 5 cuts yield: 5 NADH (15 ATP) + 5 FADH2 (10 ATP) + 23 (from Acetyls)

    • Total = 95 ATP - cost to initiate β-oxidation (2 ATP) = 93 ATP generated

Comparison of Energy Yield

• Glucose vs. Lauric Acid

  • Two glucose molecules contain 12 carbons; yield approximately 72 ATP but practically around 60 ATP.

  • Lauric acid yields about 95 ATP (with practical yield around 75 ATP).

  • Energy content comparison:

    • Glucose: 60 ATP = 16 kJ/g

    • Lauric Acid: 75 ATP = 38 kJ/g

    • Fat provides more than twice the energy per gram compared to glucose.

Whole Fat Molecule Considerations

• Factors Affecting ATP Yield

  • Number of carbons in fatty acids

  • Acetyl group count

  • Cuts required for processing

  • Cell type impacts metabolic efficiency due to different shuttles utilized in various cells.

Glycerol Metabolism via Glycolysis

• ATP Calculation (estimate based on assumptions of shuttle use):

  • Activation Costs & Yield:

    • Input costs = -1 ATP

    • Pyruvate Oxidation + Krebs Cycle yields additional ATP.

    • Total ATP from Glycerol processing becomes comprehensive depending on pathway chosen.

β-Oxidation Process

• ATP Calculations Breakdown

  • Each chain of fatty acids undergoes multiple cuts; factual calculations needed to assess NADH and FADH2 generated.

  • Include ATP costs for initiating β-oxidation in overall yield.

Acetyl-CoA Metabolism Process

• Caloric Yield Determination

  • ATP per unit from each Acetyl-CoA will depend on how many are metabolized through Krebs cycle.

Summary of ATP Yield Calculations

• Detailed analysis of total ATP yield with glycerol processing, β-oxidation, and Acetyl-CoA metabolism generally add up to substantial cellular respiration energy following fatty acid breakdown.

Practice Example

• Further Application

  • Understanding through practice questions or problem-solving exercises is encouraged to reinforce knowledge.