Lipid Metabolism Flashcards
What are the functions of lipids?
Membrane structure, fuel for energy metabolism, hormone action, electron transfer, antioxidant
Where does beta-oxidation of fatty acids occur?
Liver, heart, muscle cells, in mitochondria
How to long chain fatty acids enter beta-oxidation?
Coenzyme A attached to the fatty acid to make fatty acetyl CoA
What is the product of beta-oxidation and where does it go?
Acyl CoA, can enter TCA cycle/ox. phos. or be used for ketone formation
How is beta-oxidation regulated on a whole body scale and on a cellular scale?
Whole body: Hormonal release of fatty acids from adipose tissue
Cellular: Entry of fatty acyl CoA into mitochondria is regulated
What metabolic diseases can be caused by beta-oxidation?
Bovine ketosis, equine hyperlipidemia, diabetes mellitus
How much ATP is required to activate a fatty acid and what energy is produced?
2 ATP consumed, AMP is produced
How does the fatty acyl CoA enter mitochondria to partake in beta-oxidation?
CoA attaches fatty acyl to the carnitine shuttle, which brings fatty acyl into mitochondria and binds with another CoA while the carnitine shuttle recycles
What occurs in the first step of beta-oxidation?
Acyl CoA is dehydrogenated via Acyl CoA dehydrogenase and the hydrogen is used to reduce FAD+ to FADH2 and create a double bond
What occurs in the second step of beta-oxidation?
Water is added via hydratase which adds a hydroxyl group to the beta carbon
What occurs in the third step of beta-oxidation?
Molecule is oxidized again, NAD+ reduced to NADH via hydroxacyl CoA dehydrogenase
What occurs in the final step of beta-oxidation?
Thiolase cleaves the molecule to get acetyl CoA and acyl CoA (Which goes around the cycle again).
How does beta-oxidation change for polyunsaturated fatty acids?
Requires more enzymes to oxidize double bonds, requires 5 ATP per extra double bond
What happens to excess acetyl CoA in the liver?
Forms ketone bodies, secreted to blood and used in other tissues
What triggers lipid catabolism?
Glucagon, adrenaline
What inhibits the carnitine shuttle?
Malonyl CoA
Under what conditions and in which locations is fatty acid anabolism performed?
High energy conditions, in liver, adipose tissue, mammary tissue
What is the substrate for fatty acid anabolism and how is it carried out of the mitochondria?
Acetyl CoA, moved out by citrate shuttle
What is the primary product of fatty acid anabolism?
Palmitoyl CoA, 16 carbon chain
Where can palmitic acid be elongated?
Endoplasmic reticulum or mitochondria
When does fatty acid synthesis occur?
Times of high energy intake, increased insulin, decreased glucagon, and high glucose
How is acetyl CoA carboxylase regulated?
Stimulated by citrate (Substrate), inhibited by palmitoyl acid (Product), insulin/glucagon
