Lipid metabolism from 1000 ft
Insulin vs cortisol on protein metabolism
Why does the brain need to be able to function on ketone bodies as well as glucose?
In starvation, glucose is the first to go, and there is no way to convert fatty acids into glucose in the human body. Instead, ketone bodies serve as a mechanism to transport energy from fatty acids to the brain to maintain brain function.
Important differences between energy storage lipids and membrane lipids
Energy storage: Mostly triacylglycerols, which are of neutral charge. Exclusively utilize palmitic acid.
Membrane lipids: Mostly contain a phosphate group coupled to an alcohol, making them negatively charged. Utilize various fatty acids including unsaturated fatty acids.
If insulin falls low, ___ slows or stops in skeletal muscle cells. If it falls too low, skeletal myocytes will _____.
If insulin falls low, muscle production slows or stops in skeletal muscle cells. If it falls too low, skeletal myocytes will degrade their own protein to release it into the blood.
Utimately these amino acids would then be utilized to synthesize glucose for the brain.
Humans do not posess a mechanism to go from ____ to ____. Only in the reverse direction.
Humans do not posess a mechanism to go from Acetyl-CoA to Pyruvate. Only in the reverse direction (Pyruvate dehydrogenase).
You cannot make glucose from fatty acids!!!!
Carbohydrate metabolism from 1000 ft
Fundamental links between carbodydrate, amino acid, and lipid metabolism
Regulation of glucagon release from alpha cells
Insulin!!!! You never have high insulin and high glucagon unless something has gone very wrong.
High levels of circulating amino acids stimulate release of glucagon, as does epinephrine (sympathetic nervous system activation).
Beta islet insulin release diagram
Insulin and glucagon sensing
84-95% of human fuel storage is in the form of ___.
84-95% of human fuel storage is in the form of fat.
Where metabolism takes place in the cell
Pyruvate dehydrogenase must be irreversible in order to ____.
Pyruvate dehydrogenase must be irreversible in order to commit methyl groups on Acetyl-CoA to the citric acid cycle.
The carbon skeleton of alanine is the same as that for ____.
The carbon skeleton of alanine is the same as that for pyruvate.
Pyruvate is made from alanine via the action of alanine transaminase. The amino group for this reaction is given to α-ketoglutarate to form L-glutamate. This reaction also requires pyridoxal phosphate (PLP, aka vitamin B6) as a coenzyme.
Insulin signaling via RTKs
Glucagon/Epinephrine-regulated metabolism at 1000 ft
Various outputs of Akt
In addition to glucagon, ____ also helps stimulate glucose production and release
In addition to glucagon, epinephrine also helps stimulate glucose producUon and release
Amino acid metabolism from 1000 ft
Insulin-regulated metabolism at 1000 ft
Key pathways of amino acid metabolism
Major lipases in lipid transport regulation
Hormone-sensitive lipase is expressed in adipocytes in response to glucagon or epinephrine and triggers release of triacylglycerides by adipocytes.
Lipoprotein lipase is expressed in capillaries in response to insulin and triggers the conversion of circulating lipoprotein particles (chylomicrons and VLDL) into fatty acids to allow bordering adipocytes to absorb the fatty acids.
How do beta islet cells sense glucose?
Glut2 transports glucose into the cell and enables ATP generation via oxidative phosphorylation. In beta islet cells, ATP inhibits an ATP-gated K+ channel. Closing this channel causes depolarization of the membrane, leading to Voltage-gated Ca2+ channel opening and calcium-mediated vescile fusion and insulin release.
Dietary fat ingestion
Male and Female body fat percentages
Over these ranges is considered clinically obese.
Phosphorylation by ___ activates hormone-sensitive lipase
Phosphorylation by PKA activates hormone-sensitive lipase
Unlike carbohydrates and lipids, protein serves an additional role as _____ and thus overutilization has functional consequences.
Unlike carbohydrates and lipids, protein serves an additional role as a building block in both mitotic and post-mitotic cells and thus overutilization has functional consequences.
Especially on skeletal muscle
How fat cells release fatty acids
Fuel homeostasis following meal
Cortisol activates the expression of genes that promote ___ breakdown.
Cortisol activates the expression of genes that promote skeletal muscle breakdown.
These include E3 ubiquitin ligases that recognize sacromere components.