Biochem- Pentose Phosphate Pathway Flashcards
What is the significance of the Pentose phosphate pathway?
Produces ribose -5-phosphate and 2 NADPH
Note: it does not produce ATP;
State the significance of the R-6-P from the Pentose phosphate pathway.
Needed for nucleic acid and coenzyme synthesis.
State the significance of NADPH from the Pentose Phosphate Pathway.
1) needed for reductive synthesis of fatty acids. (Biosynthesis)
2) needed for cholesterol and steroid anabolism
3) creates a protective reduction atmosphere in O2 exposed tissue.
4) detoxification of reactive oxygen species. (Free radical rxns)
State the two phases of Pentose phosphate pathway (PPP)?
Oxidative phase (irreversible)
Non oxidative phase (reversible)
Describe Oxidative Phase Reaction 1 and give its significance.
G-6-P is oxidized into 6-phosphogluconolactone by G-6-P dehydrogenase.
It produces the first NADPH
Irreversible rxn
Regulatory step of PPP.
Describe Oxidative Phase Reaction 2 and give its significance.
6-phosphoglucanolactone is hydrolized by gluconalactonase to form 6-phospho-D-gluconate.
Describe Oxidative Phase Reaction 3 and give its significance.
— occurs in two steps.
— 6-phospho-D- gluconate is decarboxylzed to a ketoacid to from 3-keto-6-phospho-d-gluconate.
— ketoacid decarboxylzed.
— ribulose - 5- phosphate.
2 molecule of NADPH is produced.
Describe Oxidative Phase Reaction 4 and give its significance.
Ribulose -5- phosphate is converted into ribose 5 phosphate by ribulose -5- phosphate ketoisomerase via a enediol intermediate.
List the two oxidative phase reactions which NADPH is produced in the PPP?
Reactions 1&3
State the significance of PPP and Favism.
— PPP produces NADPH
— Favism is linked to a deficiency of G6PDH
— G6PDH generates NADPH, needed for reductive biosynthesis and detoxification of reactive O2 species (ex ROSes)
— a reduction in G6PDH reduces NADPH
— Reduced NAPDH increases ROSes.
— leads to haemolytic anaemia.
State the advantage of an individual experiencing Favism.
— A deficiency in G6PD protects an individual from malaria.
— malaria parasite Plasmodium falciparum is senestive to levels of ROSes.
Describe Nonoxidative Phase Reaction 1.
Ribulose-5-phosphate is epimerase into xylulose-5-phosphate by ribulose -5-phosphate 3 epimerase.
Where does the PPP occurs?
In the cytosol
— in the liver, mammary glands and adrenal cortex,
State the significance of Ribose -5- phosphate generated from the PPP.
Synthesis of nucleotides:
A) DNA
B) RNA
C) FAD
D) NAD+
E) ATP
F) Coenzyme A.
