BCH 3120 Lecture Notes - Lecture 18: Glucokinase, Ketone Bodies, Glycogen
28 Apr 2018
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March 13, 2017
Integration of Metabolism
Major Metabolic Pathways
Tissue Specific Pathways
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March 13, 2017
Not all pathways are present in each tissue
Brain: only uses glucose and ketone bodies
-Ketone bodies are usually only used under fasting conditions
-20% of oxygen is used by the brain
-Very little glycogen is stored in the brain
-Brain is very sensitive to blood glucose levels: needs 5 mM glucose in blood
Muscle: uses glucose, fatty acids, and ketone bodies
-Key place where glycogen is generated: 2% of muscle is glycogen
•Can easily go through glycolysis very quickly
•Can be mobilized faster via anaerobic oxidation
-Cannot undergo gluconeogensis: lacks G6P phosphatase
Adipose tissue:
-Major place where energy is stored: close to 600 000 kJ will be stored in a 70 kg human - enough for 3 months
•In a 70 kg person, roughly 15 kg will be adipose tissue
-Uses glucose to make glycerol-3-phosphate
-Uses free fatty acids to make acyl-CoAs
-Hormone sensitive lipase hydrolyzes TAGs
Liver:
-Most metabolically active site
-Can do everything except for ketone body catabolism
-Portal vein from intestine delivers nutrients to liver, except fatty acids, which go to the lymphatic system
-Does not compete for glucose - capable of making glucose, so it’s not that necessary to absorb from dietary
sources
-Fatty acids are the major energy source under high metabolic demand
•Under low metabolic demand, fatty acids will be stored as TAGs
-Will use amino acids to generate energy under fasting conditions: usually uses alanine and glutamate
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March 13, 2017
ATP Sources During Exercise
Phosphocreatine: ADP + PC —> ATP + C
-Under equilibrium control
-Acts as a buffer for ATP - only good for ~10 seconds
-Will favour the formation of ATP under low ATP conditions due to Le Chatelier’s Principle
Anaerobic glycolysis: occurs after phosphocreatine stores are depleted
-Flux much higher than TCA
-After 30 seconds, enough lactic acid will build up to cause muscle fatigue
Oxidative phosphorylation: occurs for muscles that perform longterm activity (ex. heart muscle, tons of mitochondria)
-Heart uses glucose, Kenton bodies, fatty acids, pyruvate, and lactate as energy sources
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Document Summary
Not all pathways are present in each tissue. Ketone bodies are usually only used under fasting conditions. 20% of oxygen is used by the brain. Very little glycogen is stored in the brain. Brain is very sensitive to blood glucose levels: needs 5 mm glucose in blood. Muscle: uses glucose, fatty acids, and ketone bodies. Key place where glycogen is generated: 2% of muscle is glycogen: can easily go through glycolysis very quickly, can be mobilized faster via anaerobic oxidation. Major place where energy is stored: close to 600 000 kj will be stored in a 70 kg human - enough for 3 months: in a 70 kg person, roughly 15 kg will be adipose tissue. Uses free fatty acids to make acyl-coas. Can do everything except for ketone body catabolism. Portal vein from intestine delivers nutrients to liver, except fatty acids, which go to the lymphatic system.
