Recording-2025-03-20T13:22:18.334Z

Fatty Acids and Lipid Metabolism

• Fatty acids are crucial lipids for energy production in cells.

• Different types of lipids exist, and their structures (especially double bonds) affect how they are metabolized.

• Lipids with carbon-carbon double bonds and those with odd numbers of carbons require specific enzymatic pathways for degradation.

Ketogenesis

• Occurs when fatty acids are released from adipose tissue and transported to the liver.

• In scenarios of low glucose levels, fatty acids undergo beta-oxidation to become four-carbon intermediates.

  • These intermediates can be utilized by various tissues like muscle and brain for energy.

• gluconeogenesis is activated to maintain blood glucose levels using intermediates produced during metabolism.

Formation of Ketone Bodies

• Two acetyl CoA units combine to form acetoacetate and beta-hydroxybutyrate via ketoacyl thiolase and HMG CoA synthase.

• Acetoacetate and beta-hydroxybutyrate are four-carbon molecules exported into the bloodstream as ketone bodies.

• When these ketone bodies reach respective cells (primarily muscle), they are converted back to acetyl CoA to be used for energy production.

Energy Regulation

• In the absence of insulin, high blood glucose and ketone body levels may lead to ketoacidosis, dramatically affecting blood pH and health conditions.

• Fatty acid synthesis occurs in the cytoplasm and involves the conversion of citrate to acetyl CoA.

  • Acetyl CoA is utilized to chain two-carbon additions to eventually produce fatty acids leading to storage as triglycerides or phospholipids.

Role of AMPK

• AMP-activated protein kinase (AMPK) acts as a significant sensor of the cell’s energy state (ATP vs. AMP levels).

• High AMP levels signal an energy-deprived state, triggering AMPK activation to inhibit fatty acid synthesis.

• AMPK regulates its targets, like acetyl CoA carboxylase, to prevent energy consumption in fatty acid production when energy is low.

Feedback Mechanisms in Metabolism

• Multiple regulatory mechanisms exist to integrate cellular signals (insulin, glucagon, AMP levels) and fine-tune metabolic pathways, like fatty acid synthesis and degradation.

• The balance between active and inactive states of regulatory proteins ensures homeostasis in lipid metabolism, reflecting the complex adaptive systems at play in cellular energy management.