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25 Cards in this Set
- Front
- Back
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1. What are the two functions of the pentose phosphate pathway?
What is a general overview of the pentose phosphate pathway? |
1. Produce NADPH
2. Produce ribose 5-phosphate -precursor to nucleotide RNA (5 c ribose sugar) Glucose 6-P --> pentose phosphate -NADPH *also produce glycolytic intermediates Pentose phosphate --> nucleotides |
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2. What is UDP-glucose a precursor for?
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1. Glygcogen
2. Lactose 3. UDP-glucuronate 4. Glucuronides 5. Carbohydrate chains in glycoproteins, glycolipids, and proteoglycans |
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3. What happens in galactose metabolism?
What happens in fructose metabolism? Into what are fructose and galactose incorporated into? |
Galactose to...
-glucose 1-P (to glycogen) -glycogen Fructose to.. -glucose 6-P (to pyruvate) Glucose metabolism |
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4. What is NADPH used for?
Three things... |
1. Reductive pathways (FA biosynthesis)
2. Detoxification of drugs by monooxygenases 3. Glutothione defense system against injury by reactive oxygen species (ROS) |
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5. What are the two phases of the pentose phosphate pathway?
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1. Oxidative
-NADPH is generated by irreversible oxidation of glucose 6-P to ribulose 5-P 2. Nonoxidative -ribulose 5-P is converted to ribose 5-P and to intermediates of the glycolytic pathway |
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6. What is the overview of the oxidative part of the pentose phosphate pathway?
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1. Glucose --> Glucose 6-P
2. Glucose 6-P --> Ribulose 5-P **convert 2 NADP+ to 2 NADPH |
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7. What is the overview of the nonoxidatve part of the pentose phosphate pathway?
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1. Ribulose 5-P --> Ribose 5-P
**used for nucleotide biosynthesis 2. Ribulose 5-P <--> Fructose 6-P 3.Ribulose5-P<->Glyceraldehyde3-P **glycolytic intermediate |
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8. What are the three products of the oxidative portion of the pathway?
What is the important enzymes? What cofactor does it require? |
2 NADPH
2 CO2 Ribulose 5-P Glucose 6-phosphate dehydrogenase NADP+ **reduces it to NADPH |
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9. What are the two reactions in the nonoxidative portion of the pathway?
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Isomerase and epimerase reactions (enzymes involved)
Isomerase -create ribose 5-P Epimerase -create glycolytic intermediate ultimately |
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10. Which enzyme transfers a 2 carbon unit to form the glyceraldehyde 3-P?
What cofactors does this enzyme require? |
Transketolase
Thiamine Pyrophosphate (TPP) Magnesium |
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11. What reaction does transaldolase catalyze?
What does it remove? What is formed? |
Glyceraldehyde 3-P to Fructose 6-P
Removes 3 C fragment Glycolytic intermediate |
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12. What pathways require NADPH?
Seven... |
1. Reduction of glutathione
2. Monooxygenases 3. FA synthesis 4. FA chain elongation 5. Cholesterol synthesis 6. Neurotransmitter synthesis 7. Nucleotide synthesis |
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13. Why is the pentose phosphate pathway a shunt?
What vitamin does NADP+ require? What is NAD+ used in? What is NADP+ used in? |
B/c C's could ultimately end back up in glycolytic pathway
Niacin Used in redox rxns (NRG producing) Use as reducing agent (not producing NRG) |
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14. What is an activated sugar?
How is an activated sugar such as UDP-glucose formed? |
Sugar attached to nucleotides
Glucose 1-P + UTP Form: UDP-glucose + PP **hydrolyze UTP so create lots of energy (highly favorable reaction) |
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15. When and where is lactose synthesized?
What enzyme is used? What are the two protein subunits of the protein? |
During lactation in the mammary gland
Lactose synthase 1. Galactosyltransferase 2. α-lactalbumin |
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16. How is UDP-glucuronate synthesized?
What enzyme is used? |
UDP-glucose --> UDP-glucuronate (salt form)
Oxidize alcohol on C-6 of glucose by a NAD+ dependent dehydrogenase UDP-glucose dehydrogenase |
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17. What are the metabolic routes of UDP-glucuronate?
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1. Proteoglycans/glycoproteins
2. Bilirubin diglucuronate 3. Glucuronides 4. Iduronate 5. UDP-xylose |
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18. Where is fructose metabolized?
How is it metabolized? What is the rate limiting steps of fructose metabolism? |
In the liver
By phosphorylation at the C-1 position and conversion to intermediates in the glycolytic pathway Aldolase B -break covalent bonds to form glyceraldhyde and dihydroxyacetone-P |
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19. What converts fructose to fructose 1-P?
What else is needed? What are the two products from fructose metabolism? |
Fructokinase
ATP 1. Dihydroxyaceton-P 2. Glyceraldhyde 3-P |
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20. What are two disturbances of fructose metabolism?
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1. Essential Fructosuria
-Fructokinase deficiency 2. Hereditary Fructose Intolerance -Aldolase B deficiency **eliminate fructose from diet b/c can be fatal |
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21. How can fructose be formed from sorbitol?
What can a build up of sorbitol in diabetics cause? |
Glucose --> Sorbitol
-aldose reductase Sorbitol --> Fructose -sorbital dehydrogenase -NAD+ to NADH + H+ Cataracts |
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22. How is galactose principally ingested?
What is it converted to? How does this happen? What does the fate of dietary galactose parallel? What can galactose be reduced to? |
As lactose
Glucose 1-P Via phosphorylation and activation to the UDP-sugar Glucose Galactitol |
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23. What are disturbances of galactose metabolism?
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1. Classical galactosemia
-deficiency of galactose 1-P-uridyl transferase 2. Galactokinase deficiency -non classical galactosemia |
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24. What enzyme converts galactose to galactose -P?
What is galactose ultimately converted to? |
Galactokinase
Blood glucose to enter glycolysis or any of the metabolic routes of glucose |
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25. What does the epimerization of UDP-glucose to UDP-galactose utilize?
What does it do? |
NAD+
Oxidize alcohol to a ketone and then reduce ketone back to alcohol **The reaction is reversible |
