The Liver and Gluconeogenesis Flashcards
Definition of glycolysis
Process of breaking down of glucose in the cytoplasm with or without oxygen
Definition of glycogenolysis
Breakdown of glycogen to glucose 1 phosphate by the sequential removal of glucose monomers via glycogen phosphorylase
Definition of gluconeogenesis
Metabolic process by which organisms produce sugars for catabolic reactions from non carbohydrate precursors
Describe the glucose requirements
Continuous
Glucose is the preferred fuel source for all tissues
Some tissues have a continuous glucose dependence
Average blood glucose conc and what happens if its too high or too low
Physiological circulating [glucose] = 3.9-6.2mM
Average fasting 4.4-5mM for most adults
2.5> = coma/death
If it rises for an extended time, dehydration, body tissue wasting and eventually death occurs
Roles of glucose
Energy source
Glucose => Pyruvate => 2ATP
Glucose => CO2 + H2O => 31 ATP
NADPH source
Needed for synthetic reactions and drug metabolism
Pentose sugar source (nucleotides, DNA)
Source of C for other sugars and glycoconjugates (mannose, galactose, glucuronic acid)
Advantages of glucose as a metabolic fuel
Water soluble, does not need a carrier in circulation
Can cross the blood brain barrier
Can be oxidized anaerobically
Disadvantages of glucose as a metabolic fuel
Relatively low yield of ATP/mole compared to FA
Osmotically active
High concentrations can directly damage cells/lead to accumulation of toxic byproducts (fructose, sorbitol)
Pathways involving glucose
Predominant pathways involving glucose are different in different tissues
All tissues use glucose
Only the liver can provide glucose for other tissues
Role of glucose in skeletal muscle
Main pathways
Function of each pathway
Glycolysis, anaerobic muscle contraction
Glycolysis/TCA, energy
Glycogen synthesis and degradation , energy store for muscle contraction
Role of glucose in heart/brain
Main pathways
Function of each pathway
Glycolysis/TCA, ENERGY
Role of glucose in adipose
Main pathways
Function of each pathway
Glycolysis
Production of glycerol phosphate for TAGS
Role of glucose in eRBC
Main pathways
Function of each pathway
Glycolysis, Energy
Pentose phosphate pathway, NADPH generation
Role of glucose in the liver
Main pathways
Function of each pathway
Glycolysis/TCA in fed state, acetyl CoA production =>FA synthesis
Pentose phosphate pathway, NADPH generation, pentoses
Glycogen synthesis/glycogenolysis, glucose glorage for other tissues
Gluconeogenesis, glucose for other tissues
Sources of blood glucose
Diet (does not last long) Liver glycogen (lasts a while) Liver gluconeogenesis (lasts the longest)