Metabolism 4 Flashcards
Glucagon and epinephrine’s effect on glycolysis
Shut down glycolysis and promote gluconeogenesis, increasing transcription of the enzymes needed for gluconeogenesis
Glucagon and epinephrine’s effect on glycogen
Promotes glycogenolysis
Gluconeogenesis
Formation of glucose from non-carbohydrate sources
What are precursors for gluconeogenesis?
Pyruvate
Lactate
Glycerol
Glucogenic amino acids
How many ATPs are required for gluconeogenesis?
6
What enzyme is required to “release” the glucose from both glycogenolysis and gluconeogenesis?
Glucose-6-phosphatase
What two cofactors are needed to “activate” pyruvate in gluconeogenesis?
Biotin and bicarbonate
How does pyruvate get converted into PEP?
Through an oxaloacetate intermediate, utilizing pyruvate kinase and PEP carboxylase
Phase I
Exogenous glucose being used in all parts of the body.
Phase II
Glycogenolysis and hepatic gluconeogenesis keep glucose levels above 60 mg/dL. Liver is no longer using glucose. Adipose and muscle decrease glucose use rates.
Phase III
Glycogenolysis and hepatic gluconeogenesis are used for glucose balance. Muscle and adipose tissue using glucose at slightly lower rates.
Phase IV
Gluconeogenesis from both kidney and liver. Only blood cells, brain, and heart are using glucose, with some muscle use still remaining. Brain begins using ketone bodies.
Phase V
Gluconeogenesis from both kidney and liver. Only brain (at diminished rate), blood cells, and renal medulla are using glucose. Brain continues using ketone bodies.
What body parts have an absolute requirement for glucose?
The brain, blood cells, and lens of the eye
How are odd-numbered fatty acids put through GNG?
They are converted to propionyl coA, then to succinyl coA, then to pyruvate.
How is glycerol introduced into GNG?
It is converted into DHAP
How is aspartate put into GNG?
It is converted to oxaloacetate
How are lactate and alanine introduced into GNG?
They are converted into pyruvate
Why are neonates at risk for hypoglycemia?
PEP carboxykinase is needed for the first steps in gluconeogenesis, which takes a few hours after birth to activate
Describe the Cori cycle.
RBC’s break down glucose by glycolysis, then shuttles it through LDH and makes lactate. This lactate is transported back to the liver, where it undergoes gluconeogenesis and the glucose is transported back to the red blood cell.
How is the Cori cycle different in muscle?
Pyruvate is not made into lactate, but into alanine, which is then transported back to the liver, which uses the carbon backbone for GNG and creates urea as a byproduct
What is the major source for GNG during an overnight fast?
Fatty acids
Precursors to propionyl coA
Valine Isoleucine Cholesterol Odd chain fatty acids Phtanic acid
Special considerations of oxaloacetate transport
OA is formed in the mitochondria, but cannot be transported out. It must first be converted into malate, then converted back to OA when in the cytosol. Requires biotin.
