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What are the 2 parts of the Pentose pathway?
- Oxidative Phase: Get NADPH
- Non-Oxidative Phase: Reshuffling
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What is Ribose-5-P used for?
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What reactions/enzymes form NAPDH?
- G6P --> 6-Phosphoglucanolactone (G6P DH)
- 6-Phophogluconate --> Rubulose-5-Phosphate (6-phosphogluconate DH)
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What occurs due to a deficiency in G6P DH?
- Low NAPDH concentration
- Manifested in RBC
- Hemolytic anemia
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What is NAPDH directly used for in RBCs?
To reduce glutathione and allow the breakdown of H2O2 to H2O
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Where do the molecules of the pentose pathway re-enter glycolysis?
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What enzyme's activity is measured in order to determine thiamine deficiency?
Transketolase
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If only NADPH is needed, how does the pentose pathway proceed?
- Oxidative reactions to make NADPH
- Nonoxidative reactions to make F6P and GAP
- THEN, these are remade into G6P to redo again
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If NADPH and ribose-5-P are needed, how does the pentose pathway proceed?
- Oxidative reactions make NADPH and ribulose-5-P
- Ribulose 5-P is converted to ribose-5-P
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If only ribose-5-P is needed, how does the pentose pathway proceed?
Nonoxidative reactions only - in reverse
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What inhibits G-6-P dehydrogenase?
High NAPDH
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If NADPH and pyruvate are needed, how does the pentose pathway proceed?
- Normally through oxidative and non-oxidative
- Then continues through glycolysis upon formation of F6P and GAP
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What is the structure of sucrose?
Glucose (alpha 1,2) Frucose
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What is the structure of lactose?
Galactose (beta 1,4) Glucose
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What enzyme function is seen in frucose, galactose and glucose metabolism?
An initial kinase that sequesters the molecule in the cell
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Where do the products of frucose matabolism enter glycolysis?
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What transporter is used to transport fructose into the liver?
GLUT-5
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Describe fructosuria:
- Deficiency: Fructokinase
- Benign, asymptomatic
- 90% is eventually metabolized
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Describe fructose intolerance:
- Deficiency: Aldolase B
- Build up of F-1-P
- Inhibits gluconeogenesis and glycogenolysis
- Causes: Hypoglycemia and lactic acidosis
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What is lactose made of in the mammary gland and using what enzyme?
- Glucose + UDP-Galactose
- Enzyme: Lactose synthase
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What are the final products of galactose metabolism and where do they go?
- Glucose-6-P --> glycolysis
- Glucose --> other tissues
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How is glucose formed from glucose-6-P in the metabolism of galactose?
Glucose-6-phosphatase
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Describe non classical galactosemia
- Deficiency: Galactokinase
- Causes: Build up of galactose
- Result: Formation of cataracs due to build up of galactitol
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Describe classical galactosemia:
- Deficiency: Galactose-1-P Uridylyltransferase
- Causes: Accumulation of galactose-1-P
- Result: Severe neurological effects and liver damage
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What 2 enzymes do the reshuffling during nonoxidative phase of the pentose pathway?
- Transketolase
- Transaldolase
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What cofactor is used during the non-oxidative phase and by who?
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