Energy Metabolism Lecture Recording 2025-03-24 Flashcards

Introduction to Energy Metabolism

• Most complex topic covered in class.

• Two major categories of chemical reactions:

  • Catabolism: The process of breaking down macronutrients into smaller units (e.g., glucose, fatty acids, amino acids).

  • Anabolism: The process of building up small units into larger components (e.g., amino acids → proteins, sugars → glycogen).

Intermediates in Metabolism

• Intermediates are substances formed during catabolic or anabolic pathways that are not the end products.

Macronutrients

• Carbohydrates, proteins, and fats are critical for energy production.

• ATP (Adenosine Triphosphate): The primary energy currency of cells derived from metabolic processes.

• Breakdown processes:

  • Carbohydrates to glucose

  • Triglycerides to fatty acids and glycerol

  • Proteins to amino acids

• All converge to form Acetyl CoA, which feeds into the Krebs Cycle (Citric Acid Cycle).

Krebs Cycle and Electron Transport Chain

• The Krebs Cycle produces energy (ATP) through a sequence of reactions in mitochondria.

• The Electron Transport Chain (ETC) follows, where the bulk of ATP is generated.

• Different metabolic pathways yield different amounts of energy.

ATP as Energy

• ATP releases energy by breaking phosphate bonds:

  • ATP → ADP (Adenosine Diphosphate)

  • ADP → AMP (Adenosine Monophosphate)

• The energy from these reactions is critical for various bodily functions.

Redox Reactions

• Oxidation-Reduction (Redox): Involves the transfer of electrons.

  • Oxidation: Loss of electrons

  • Reduction: Gain of electrons

• NAD (Nicotinamide Adenine Dinucleotide) and FAD (Flavin Adenine Dinucleotide) act as electron carriers (coenzymes) and are crucial in metabolic pathways.

Cellular Respiration

• Aerobic Respiration: Requires oxygen and yields 30-32 ATP per glucose molecule.

• Anaerobic Respiration: Occurs without oxygen yielding only 2 ATP.

Metabolic Pathways

• Key metabolic processes:

  • Glycolysis: Breakdown of glucose into pyruvate.

  • Link Reaction: Pyruvate converted to Acetyl CoA.

  • Krebs Cycle: Acetyl CoA enters, generating ATP and reducing equivalents (NADH, FADH2).

  • Electron Transport Chain: Uses reducing equivalents to produce ATP.

Fat Metabolism

• Triglycerides broken down into glycerol and fatty acids, which can be converted to glucose and Acetyl CoA, respectively.

• Beta Oxidation: The process of breaking down fatty acids into Acetyl CoA.

Protein Metabolism

• Proteins can be converted into glucose (glucogenic) or fat (ketogenic) after deamination (removal of the amino group).

• Process of nitrogen removal results in urea production, which is excreted.

Energy Dynamics in Fasting and Feasting

• Fed State: Energy storage occurs (glycogen, fats, proteins).

• Fasting State: Energy breakdown occurs (glycogen and fat utilization).

• Short-term fasting leads to increased reliance on amino acids for glucose production; long-term fasting primarily uses fat stores.

Summary

• All macronutrients contribute to the formation of Acetyl CoA, enabling the Krebs cycle and subsequent ATP production.

• Importance of balanced intake of macronutrients to maintain energy production and metabolic function.

Conclusion

• Energy metabolism is complex, involving numerous pathways; understanding these is essential for fields such as kinesiology and dietetics.

• Regular review of material and self-testing recommended for mastery.