Mobilization of Fat Stores for Energy

Four vocabulary flashcards covering key terms involved in triglyceride mobilization, fatty acid transport, and activation for energy production.

triacylglycerols

fatty acid esters of glycerol with three fatty acid chains

beta oxidation

catabolism of fatty acids for energy

catabolism of fats

triglycerides are mobilized from adipocytes for sending to target organs: heart, muscle, kidney; organs oxidize fatty acids

adipocyte

contains fat globules that take up most of the cell; they are distributed throughout the body as brown adipose, SQ white adipose, and visceral white adipose

sources of fatty acids in animals

diet, storage in adipocytes, converting carbs to fats, autophagy (self-eating)

energy storage times

glucose stores last the least amount of time; glycogen lasts about 24 hours; protein is next; fats last the longest, up to several weeks

reasons that fats provide more energy than carbohydrates

Fats have many carbons + are highly reduced, allowing them to undergo many oxidation cycles; fats are anhydrous and can be backed into adipocytes without water needed

triglyceride storage sites

adipose tissue; surrounding muscle cells

glucagon and epinephrine signaling

binds to a GCPR, which activates AC, generating cAMP and then PKA. PKA phosphorylates perilipins surrounding lipid droplets, opening it. ATGL then enters and removes one FA from a triglyceride, generating a diglyceride. PKA also phosphorylates HSL, activating it to enter the lipid droplet and remove an FA from the diglyceride, creating a monoglyceride. Finally, MGL (resident) removes the final FA, releasing the final FFA and the glycerol backbone.

pathway of FFAs

FFA leaves adipocyte and binds to serum albumin in blood; FFA is released when a fatty acid transporter is encountered on the surface of a muscle cell (myocyte). Inside, the FFA can be broken down for energy by entering the mitochondria, which breaks them down into Acetyl-CoA for the CAC.

serum albumin

A protein in blood plasma that is complexed with FAs. It is released from the liver, travels through blood, and picks up and transports FAs, steroid hormones, and drugs.

fates of glycerol

Glycerol → G3P → DHAP → Ga3P → pyruvate (if ATP needed fast); or →→→ glucose (for BG regulation)

fatty acid activation

fatty acid + ATP → acyl-adenylate (AMP) + PPi; acyl-AMP + CoA-SH → acyl-CoA (activated fatty acid) + AMP

carnitine

carries acyl groups across the IMM using the carnitine carrier protein; carnitine binds to acyl-CoA to form acylcarnitine + releasing CoA-SH (via carnitine palmitoyl transferase I. This molecule is transported across the membrane, where carnitine palmitoyl transferase II binds a new CoA-SH to the acyl group, reforming acyl-CoA + releasing carnitine, which goes back to the IMS through the transporter.