Integration Of Metabolism Flashcards
Which organ is the only one capable of carrying out all the major pathways of metabolism?
Liver
Which three key molecules act as metabolic junction points?
Glucose 6 phosphate, pyruvate and acetyl CoA
The liver receives blood from the enteric circulation via
Portal vein and from the periphery via the hepatic artery
Describe why the liver is considered the MVP of metabolism
Processes most incoming nutrients
Responds quickly to dietary conditions
Maintains constant concentrations of nutrients in blood regardless of food intake
Synthesizes and secretes proteins
Processes and detoxifies toxins and wastes
What does the liver primarily depend on for its own energy needs?
Beta oxidation of FAs
Describe metabolic pathways used by adipose
Synthesizes and stores TAGs as signaled by insulin/fed state
Uses FAs from chylomicrons and VLDL to make TAGs
Degrades TAGs and releases FAs and glycerol for other tissues to use as signaled by glucagon/epinephrine (hunger and exercise)
White adipose
Accumulated fat from surplus calories
Subcutaneous, large effect on hormone regulation
Brown adipose
Has high levels of thermogenin
Burns calories and generates them as heat (the good fat)
The brain highly depends on what for energy?
Blood glucose
Explain astrocytes function in metabolism in the brain
Astrocytes contain some glycogen
Breaks down to release glucose which can be used by neurons
Lactate released from astrocytes used as well
What occurs in the brain during starvation?
Brain switched to metabolism of KBs for energy needs
Metabolized by the TCA cycle
Prevents protein breakdown for energy purposes
Uses amino acids for synthetic purposes instead (i.e. make neurotransmitters and peptide hormones)
Cardiac muscle is exclusively aerobic or anaerobic?
Aerobic as evidenced by the density of mitochondria in heart muscle
Metabolic pathways in cardiac muscle
Complete oxidation of glucose via TCA cycle, oxphos and beta oxidation of FAs serve as major fuel
Also use KBs (consumes acetoacetate in preference to glucose)
Also can use (branched) amino acids
Describe metabolic pathways in skeletal muscle
Rich in glycogen (contains 75% of the body’s glycogen stores)
Glycogen readily broken down to G6P and used by muscle for glycolysis
Lacks glucose 6 phosphatase so muscle retains glucose (proffered fuel)
Also uses FAs and KBs
Describe the phosphagen system
Phosphocreatine + ADP -> creatine -> ATP
Reversible reaction: forward during activity and reversed during recovery
Highest speed but lowest energy produced
Quick exhaustion of ATP stores replenished by metabolism of phosphocreatine
Describe the generation of ATP by anaerobic glycolysis and glycogenesis
Further intense activity (past the ATP-PC phase)
Oxidation of free blood glucose or glycogen
Glycogen -> G6P -> pyruvate -> lactate
Must shift to longer more sustainable energy production system