BCHM-3050 Lecture Notes - Lecture 17: Insulin Resistance, Insulin Receptor, Diabetes Mellitus Type 2
26 Jun 2018
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Chapter 17: Interorgan and Intracellular Coordination of Energy Metabolism in Vertebrates
Interdependence of Major Organs
Interconnected chemical reactions in a complex multicellular organism
Major Organs: brain, muscle, liver, adipose tissue, heart
Major Fuel Reserves: triacylglyceroles (adipose tissue), protein (skeletal muscle), glycogen (liver and
muscle)
Each tissue requires a fuel it can use to meet its energy needs
Fuel Characteristics of Major Organs
Brain:
oFastidious – requires 120 g/day of glucose
60% of a resting human’s daily consumption of glucose
o20% of total oxygen consumption.
oNO FUEL RESERVES – but brain can adapt to fasting and use ketone bodies.
Ketone Bodies : acetone, acetoacetic acid, and B-hydroxybutarate (breakdown products
of fatty acids)
Muscles:
oUses glucose, fatty acids, ketone bodies.
When at rest – fatty acids are primary fuel
Under exertion – stored glycogen is primary fuel
oMuscle lacks G6P so glucose released by Glycogenolysis cannot be exported for use by other
tissues.
oLactate is released during exertion because glycolysis produces pyruvate faster than the citric
acid cycle can use it.
Heart:
oWork output less variable than that of skeletal muscle and continuous
oHighly AEROBIC, but no energy reserves except a little creatine phosphate.
oRequires continuous supply of fuel and oxygen
Adipose Tissue:
oMajor fuel depot – through stored TAG
oSome glucose metabolism via glycolysis must occur for synthesis of G3P for TAG synthesis.
oWhen glucose falls, free fatty acids are released for use by other tissues
Liver:
oSynthesis of fuel components for other tissues – includes fatty acid synthesis and glucose
synthesis, both from glycogen mobilization and gluconeogenesis.
oMalonyl-CoA levels regulate fatty acid metabolism through inhibition of carnitine
acyltransferase I, controlling fatty acid transport into mitochondria.
oLiver buffers blood glucose partly through action of a high Km hexokinase (glucokinase) and
partly through control of the intracellular location of glucose transporters.
Blood:
oVehicle of gas transport and metabolite transport
oRBCs, which are half of the total blood volume meet their energy needs primarily from
glycolysis, NO MITOCHONDRIA
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Document Summary
Chapter 17: interorgan and intracellular coordination of energy metabolism in vertebrates. Interconnected chemical reactions in a complex multicellular organism. Major organs: brain, muscle, liver, adipose tissue, heart. Major fuel reserves: triacylglyceroles (adipose tissue), protein (skeletal muscle), glycogen (liver and muscle) Each tissue requires a fuel it can use to meet its energy needs. Brain: fastidious requires 120 g/day of glucose. 60% of a resting human"s daily consumption of glucose: 20% of total oxygen consumption, no fuel reserves but brain can adapt to fasting and use ketone bodies. Ketone bodies : acetone, acetoacetic acid, and b-hydroxybutarate (breakdown products. Muscles: of fatty acids: uses glucose, fatty acids, ketone bodies. When at rest fatty acids are primary fuel. Heart: work output less variable than that of skeletal muscle and continuous, highly aerobic, but no energy reserves except a little creatine phosphate, requires continuous supply of fuel and oxygen.
