Significance: Primary energy source for the body.
Advantages:
More compact storage than glycogen.
Specialized storage in dedicated cells.
Unlimited capacity for storage.
Processes:
Fatty acid degradation occurs in mitochondria.
Ketone bodies produced serve as alternative energy source to glucose, sparing muscle protein for gluconeogenesis.
Structure: Long-chain hydrocarbons with carboxylic acid tails.
Variability: Chain lengths range from 3 to 24 carbons.
Properties: Amphipathic; contains a polar end (carboxylic acid) and a hydrophobic tail.
Structure Examples:
Common names and systematic names provided for various lengths and double bond configurations.
Shorthand Notation: Presented for easy reference of fatty acids.
Diet
TG absorbed in intestines → chylomicrons → FA absorbed in bloodstream
Adipose tissue
Glucagon signals the release of FA from adipose tissue to the bloodstream
Liver
Excess glucose in the liver (not being used for ATP synthesis or glycogen synthesis) is converted into FA → TG → VLDL (very low density lipoprotein) to be used or stored in adipose tissue
Energy Storage: Triacylglycerol form.
Membrane Structure: Integral to cellular architecture.
Second Messengers: Prostaglandins and thromboxanes derived from fatty acids; some are essential in diet.
Composition: Glycerol molecule esterified to three fatty acids.
Energy Storage: The principal fat energy storage form in adipocytes.
Structures Overview: Various structures of phospholipids, including phosphatidic acid and phosphatidylcholine.
Head Groups: Diverse molecules that interact with phosphate groups present.
Phospholipid Arrangement: Carboxylic acid end faces water; hydrophobic tails exclude water, creating bilayer and micelle structures, essential for cellular function.
Triggers: Release involves glucagon and epinephrine, leading to cAMP rise.
Enzymatic Action: Requires actions from ATGL, HSL, and monoglyceride lipase.
Enzyme Interactions: Detailed steps of triglyceride breakdown with the roles of ATGL, HSL, and MGL highlighted.
Transport Mechanism: Free fatty acids travel bound to serum albumin; shorter fatty acids require no binding.
Glycerol Conversion: Glycerol metabolized to glycerol-3-phosphate via glycerol kinase, which is liver-specific.
Process Description: Fatty acids oxidized in two-carbon segments through beta-oxidation.
Feeding Studies: Findings from studies lead to the identification of oxidation patterns.
Implications: Differentiation in urine outcomes for even vs. odd-numbered carbon chain fatty acids indicates breakdown patterns in beta-oxidation.
Reaction Breakdown: Conversion of fatty acids through a series of oxidations and bond cleavages producing acetyl-CoA.
Comparison: Similarities between fatty acid oxidation and TCA cycle reactions, highlighting parallels in metabolic pathways.
Reactions Flow: Detailed mechanism showcasing the transformation of acyl-CoA through different oxidation stages.
Overall Process: Activation, transport, oxidation process culminating in acetyl-CoA production within mitochondria.
Activation Process: Description of how fatty acids are activated via fatty acyl-CoA synthetase, requiring ATP as part of the process.
Step-by-Step: Summary of key enzymes and processes involved in mitochondrial fatty acid oxidation.
Mechanism: Details of carnitine's role and associated enzymes in transporting fatty acids.
Regulation: Malonyl-CoA's inhibitory role on CPT-I discussed.
Production and Regulation: Formation and regulation effects on fatty acid oxidation and synthesis pathways.
Enzyme Functions: Detailed information on specific enzymes involved in the oxidation of saturated fatty acids.
Variety of Isoforms: Specific enzymes designated for different chain-length fatty acids (Short, Medium, Very Long Chain).
Mechanism and Steps: Description of how very long-chain and branched fatty acids are oxidized using acyl-CoA oxidase forms.
Calculation: Breakdown of ATP yield from oxidation of C18:0 to carbon dioxide and water following fatty acid degradation process.
Mechanism Differences: Variations in the oxidation pathways of unsaturated fatty acids compared to saturated ones.
Further Pathways: Enzymatic actions required to navigate challenges of double bonds in unsaturated fatty acids.
Finalize Pathways: Steps leading to successful oxidation after addressing double bond conditions.
Oxidative Progression: Final processes leading to the generation of acetyl-CoA from unsaturated fatty acids.
Isomerization Impact: Role of isomerization in facilitating continued oxidation of unsaturated fatty acids.
Differences in Yield: Comparison of ATP yield based on double bond positions between saturated and unsaturated fatty acids.
Pathway Specifics: Process for handling propionyl-CoA during the final degradation round of odd-chain fatty acids highlighted.
Yield Considerations: Detailed breakdown of ATP yield accounting for conversions of propionyl-CoA and subsequent metabolic processes.
Notable Processes: Various oxidation mechanisms (alpha-, omega-, and peroxisomal) relevant to specific branched-chain fatty acids.
Electron Transfer Mechanism: Explanation of how FADH2 from fatty acid degradation interacts with the electron transport chain.
Function: Importance during glucose deprivation as an alternative fuel source.
Structural Steps: Overview of the enzymatic processes contributing to the synthesis of various ketone bodies.
Fate of Acetone and Others: Acetone’s fate outlined; significant metabolic transformations of hydroxybutyrate and acetoacetate stated.
Mechanisms: Steps detailing how fatty acid levels and energy status influence ketone body production.
Graphical Depiction: Changes in free fatty acids, glucose, and ketone concentrations during fasting stages.
Defects in Oxidation: Connection of various genetic mutations to specific metabolic disorders like glutaric acidemia and the consequences on fatty acid oxidation.
Indicators: Information on specific deficiencies (e.g., carnitine) leading to energy and transport problems in fatty acid metabolism.
MCAD: Frequency, genetic background, hypoglycemia triggers, and metabolic consequences explained.
Disease Overview: Brief exploration of disorders related to peroxisomes, including Zellweger syndrome, Refsum disease, highlighted challenges related to fatty acid oxidation.
Etiology and Effects: The role of hypoglycin and resultant metabolic disturbances detailed.
Long-Term Adaptations: Overview of enzyme regulation in response to caloric intake detailing up-regulation and down-regulation.
Regulatory Events: Insulin's role in promoting or inhibiting specific pathways within fatty acid metabolism.
Impact of Regulators: How ketone bodies impact hormone-sensitive lipase activity in regulation of fatty acid synthesis and oxidation.
Mechanistic Understanding: Steps detailing glucagon's role in activating fatty acid mobilization and gluconeogenesis.
Reiteration of Case Study: Revisits the two-month-old child and highlights signs and conditions noted.
Review Questions: Set of questions posed for students, focusing on metabolic processes during exercise and identifying enzyme defects based on observed conditions in infant patients.