Metabolism Flashcards
Ethanol metabolism
Ethanol converted to acetaldehyde by alcohol dehydrogenase and NAD+
Acetaldehyde converted to acetate by acetaldehyde dehydrogenase and NAD+
NAD+ is limiting reagent
Metabolic changes seen as result of ethanol metabolism
Increased NADH/NAD+ ratio leads to:
- lactic acidosis
- fasting hypoglycemia
- hepatosteatosis
Fomepizole
Inhibits alcohol dehydrogenase. Used as antidote for methanol or ethylene glycol poisoning
Site of fatty acid sythesis
Acetyl coA produced in mitochondria; fatty acid synthesis occurs in cytosol
Site of ketogenesis
mitochondria
Metabolic processes that can happen in cytosol or mitochondria
Heme synthesis, urea cycle, gluconeogenesis
Mutase function
Relocates a functional group within a molecule
Difference between a kinase and a phosphorylase
Kinase uses ATP to add high energy phosphate. Phosphorylase adds inorganic phosphate without using ATP
Carbamoyl phosphate synthetases
I: rate limiting enzyme in urea cycle
II: rate limiting enzyme in de novo pyrimidine synthesis
Phosphofructokinase-1
Rate limiting enzyme in glycolysis
Fructose-1,6-bisphosphatase
Rate limiting enzyme in gluconeogenesis
Isocitrate dehydrogenase
Rate limiting enzyme in TCA cycle
Glycogen synthase
Rate limiting enzyme in glycogenesis
Glycogen phosphorylase
Rate limiting enzyme in glycogenolysis
G6PD
Rate limiting enzyme in HMP shunt
Glutamine phosphoribosylpyrophosphate amidotransferase
Rate limiting enzyme in de novo purine synthesis
Acetyl co-A carboxylase
rate limiting enzyme in fatty acid synthesis
canitine acetyltransferase I
rate limiting enzyme in fatty acid oxidation
HMG-CoA synthase
rate limiting enzyme in ketogenesis
NADPH function
Produced in HMP shunt. Used in anabolic processes, respiratory burst, cytochrome P450 system, and glutathione reductase
Hexokinase vs glucokinsae
Hexokinase: Used by most tissues to convert glucose to glucose-6-phosphate. Has high affinity but low capacity and is not affected by insulin
Glucokinase: Used by liver and beta cells of pancreas to convert glucose to glucose-6-phosphate. Has low affinity but high capacity and is induced by insulin so that excess glucose is stored in the liver in times of excess.
Either way, step requires ATP (carried out by kinase)
Pyruvate dehydrogenase complex
Converts pyruvate to acetyl coA using NAD+ as cofactor
Possible pathways for pyruvate
1) alanine
2) oxaloacetate: regenerate for TCA cycle, gluconeogenesis
3) acetyl coA: TCA cycle
4) lactate
Krebs cycle intermediates
Pneumonic: citrate is kreb’s starting substrate for making oxaloacetate
- citrate
- isocitrate
- alpha-ketoglutarate
- succinyl coA
- succinate
- fumarate
- malate
- oxaloacetate
Classic Galactosemia
Impaired galactose-1-phosphate metabolism by galactose-1-phosphate uridyltransferase. Presents with vomiting, lethargy, and failure to thrive soon after breastfeeding begun
Anastrozole
Aromatase inhibitor
Galactokinase deficiency
Galacticol accumulates. Relatively mild. Galactose in blood and urine. Infantile cataracts, failure to track objects, failure to develop social smile.
Essential amino acids
Glucogenic: Met, Val, His
Glucogenic/ketogenic: Ile, Phe, Thr, Trp
Ketogenic: Leu, Lys
Acidic amino acids
Asp and Glu, neg charge at body pH
Basic amino acids
Arg, lys, his. No charge at body pH
Hyperammonemia
Excess NH4+ which depletes alpha-ketoglutarate, leading to inhibition of TCA cycle.
Treat by limiting protein and giving lactulose to acidify GI tract and trap NH4+ for excretion.
