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Fatty Acid Metabolism Complete Summary
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Fatty acid synthesis, oxidation and ketone body metabolism content
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Fay Acid Metabolism• Fats account for 83% available energy
o More fat stored than protein/glycogen
o Higher energy yield per gram
WHYS USE FATTY ACIDS FOR ENERGY STORAGE
• Catabolism = oxidative
• Carbon in fatty acids = reduced
o Its oxidation yields the most energy possible
• Fatty aids = not hydrated
o Can pack more closely in storage tissues
o Not associated with water molecules
o Mono and polysaccharides ARE associated with water
TRIACYLGLYCEROLS
• TAGs = major form of storage energy in the body
• Made of a glycerol molecule linked to 3 fatty acids
• Stored in adipocytes/adipose tissue
• FA from diet are converted into TAG after absorption à transported to cells
for breakdown
• Release of FA from adipose tissue = triggered by hormones
o Activation of triacylglerol lipase
o Hormone =
§ Glucagon
§ Epinephrine
§ ACTH – adrenocorticotropic hormone
MECHANISM
• Hormone binds to receptor
• Activation of adenylyl cyclase
• Produces cAMP
• Activates protein kinase
• Phosphorylation of TAG lipase
• TAG lipase can release 1 FA at a time
*caffeine slows down the breakdown of
cAMP
à more TAGs will be broken down because
signal proliferates
, SERUM ALBUMIN
• Most abundant protein in the bloodstream
• 3 functions =
o Provides 80% of osmotic pressure of blood plasma
o Major macromolecular anion in blood
§ Important buffering capacity
o Major transport vehicle for hydrophobic substances
§ Fatty acids
• Free [FA] in blood = 0.1nM
• [FA bound to serum albumin] = 1mM
FATTY ACIDS AND OBESITY
• High levels of circulating FFA à
o Altered deposition + accumulation of triglycerides in liver, muscle +
adipose tissue
• Altered fat accumulation à cascade of signals
o Stress + inflammatory responses + metabolic dysfunction
• Adipose tissue = endocrine organ
o Role in integration of system metabolism
o Secretion of signaling proteins
§ Adipokines
B-OXIDATION OF FA
• FA must be degraded by removal of 2C units
• Occurs in mitochondria
• 2C unit is released as acetyl CoA NOT free acetate
o Allows for activation of FA for oxidation
o Acyl CoA synthetase à condenses FA with CoA
o Formation of CoA ester = energetically expensive
§ Simultaneous hydrolysis of ATP to AMP and PPi
• Coupling!!
§ Subsequent PPi (pyrophosphate) hydrolysis drives the reaction
strongly forward (otherwise rxn would be close to equilibrium
even with ATP hydrolysis)
• Process begins with oxidation of carbon that is B to carboxyl carbon
• Repeated sequence of 4 reactions
o Rxn 1-3 = creation of carbonyl group at B-C
§ Oxidation
§ Hydration
§ Oxidation
o Rxn 4 = cleavage of B-keto ester in reverse Claisen condensation
§ Claisen condensation = C-C bond forming reaction that occurs
between 2 esters or one ester + another carbonyl compound in
the presence of a strong base à results in B-keto ester or B-
diketone
o A 16C FA goes through the cycle 7 times (2C removed each cycle)
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