Chapter 15 Flashcards
What are the products of the pentose phosphate pathway?
Ribose-5-phosphate and NADPH
What is ribose-5-phosphate used for?
Synthesis of nucleic acids
What is the purpose of distinct active sites for NADH and NADPH?
Oxidation and reduction pathways occur at the same time within the cell
Where does the pentose phosphate pathway occur?
Cytosol
What is the concentration of [NAD+]/[NADH] in the cytosol?
[NAD+]/[NADH] = 1000
What is the concentration of [NADP+]/[NADPH] in the cytosol?
[NADP+]/[NADPH] = 0.01
Is the oxidative phase of the pentose phosphate pathway reversible? Why or why not?
No, unidirectional due to decarboxylation
What is the carbon product of the oxidative phase of the pentose phosphate pathway?
Ribulose-5-phosphate (Ru5P)
How many NADPH are produced during the oxidation phase of glycolysis?
3 G6P -> 6 NADPH (2 per G6P)
What is the rate-limiting enzyme in the pentose phosphate pathway?
Glucose-6-phosphate dehydrogenase (first reaction; oxidizes G6P)
What is a lactone?
Cyclic ester (ring with a C=O)
What is the structure of G6P?
Hemiacetal
What is the first reaction of the oxidative phase of the pentose phosphate pathway?
G6P -> 6-Phosphoglucono-delta-lactone using the enzyme G6PDH
What is the second reaction of the oxidative phase of the pentose phosphate pathway?
6-Phosphoglucono-delta-lactone -> 6-Phosphogluconate using the enzyme 6PGL
What is the third reaction of the oxidative phase of the pentose phosphate pathway?
6-Phosphogluconate -> Ru5P using the enzyme 6PGDH
What is the structure of Ru5P?
Penta-ketose
What is the function of glutathione?
Reduce peroxides to alcohol and water
What does the body need to produce in order to deal with oxidative stress?
NADPH
What are the chemical reactions that the body uses to deal with oxidative stress?
GSSG + NADPH -> 2 GSH + NADP+
2 GSH + ROOH -> GSSG + ROH + H2O
What molecule(s) is Ru5P converted to after the oxidative phase of the pentose phosphate pathway?
R5P or Xu5P
What enzyme is used to convert Ru5P to R5P?
Ribulose-5-phosphate isomerase (RPI)
What enzyme is used to convert Ru5P to Xu5P?
Ribulose-5-phosphate epimerase (RuPE)
Where does RuPE epimerize Ru5P?
3 carbon
What isomerization is done to Ru5P?
Ru5P (ketose) to R5P (aldose)
What is the function of transketolase?
2 carbon transfers
What is the function of transaldolase?
3 carbon transfers
What are the ultimate products of the C-C bond arrangement phase of the pentose phosphate pathway?
2x F6P (6 carbons) and 1x GAP (3 carbons)
What happens in the breakdown of fructose in muscle tissue?
Converted to F6P by hexokinase and enters glycolysis
Why can’t fructose be directly converted to F6P in the liver?
Hexokinase isn’t present in the liver
What enzyme acts on fructose in the liver?
Fructokinase; converts to F1P
Which enzyme forms glyceraldehyde from F1P in the liver?
Fructose-1-phosphate aldolase (aldolase type B)
What enzyme converts glyceraldehyde to glycerol?
Alcohol dehydrogenase
What enzyme converts glyceraldehyde to G3P?
Glyceraldehyde kinase
What is glycerol used for?
Fatty acid synthesis
What is glycerol-3-phosphate used for?
Glycerophospholipid synthesis
