Pentose phosphate pathway Flashcards
The three metabolic pathways of glucose are?
Oxidation via glycolysis to yield pyruvate, ATP & NADH
Formation of polysaccharides
Oxidation via PPP to yield ribose-5-phosphate & NADPH for reductive biosynthesis
An alternative metabolic pathway for glucose oxidation in which no ATP is generated is called?
Pentose phosphate pathway (PPP)
PPP is also known as?
Hexose monophosphate shunt (HMP Shunt)
6-Phosphogluconate pathway
Four properties of PPP are?
More complex pathway than glycolysis
More anabolic in nature
Takes place in the cytosol
Concerned with the biosynthesis of NADPH & pentoses
Four tissues that are highly active in HMP shunt are?
Adrenal gland
Liver
Testes
Lactating mammary gland
The two products of PPP are?
NADPH
Pentose
Four importance of NADPH are?
Biosynthesis of fatty acids and steroids
detoxification of drugs
Phagocytosis requires NADPH
NADPH keeps the Fe2+ iron of haemoglobin in a reduced state
Two importance of Pentoses are?
Use in the synthesis of nucleic acids and many nucleotides
Produces carbohydrates for cell wall synthesis for some growing organisms
Nucleic acid examples are?
DNA
RNA
Nucleotide examples are?
ATP
NAD+
coA
HMP Shunt sequence of reactions are divided into?
Two phases
The first phase of the HMP shunt is?
Oxidative phase(non-reversible)
The oxidative phase has how many ___reactions
3
In the first reaction, __1__ catalyzes the conversion of Glucose-6-phosphate into __2__
- Glucose-6-phosphate dehydrogenase(G6PD)
2. 6-phosphogluconolactone
The two products of the first reaction are?
6-phosphogluconolactone and NADPH
In the second reaction, 6-phosphogluconolactone is hydrolyzed into?
6-phospho-D-gluconate
Gluconolactonase
In the third reaction, oxidative decarboxylation of 6-phospho-D-gluconate is done to produce?
Ribulose-5-phosphate
NADPH
(6 phosphogluconate dehydrogenase)
PPP is most active in?
Cells where large amounts of lipids are synthesized (liver, adipose tissue, mammary glands)
Cells that are at high risk for oxidative damage (RBC)
Under the oxidative phase of PPP, Glucose-6-phosphate undergoes __1__ & _2__ to give a pentose, and D-ribulose-5-phosphate
Dehydrogenation
Decarboxylation
Non-oxidative phase has ___ reactions
2
In the first reaction, ribulose-5-phosphate is converted to ribose-5-phosphate by?
Ribulose-5-phosphate isomerase
Ribulose-5-phosphate may also be converted to xylulose-5-phosphate by?
Ribulose-5-phosphate epimerase (main reaction)
__ &__ catalyze the interconversions of trioses, Pentoses & hexoses
Transketolase
Transaldolase
A TPP requiring enzyme that transfers two carbon units from a ketose to an aldose is called?
Transketolase
Transketolase catalyzes how many reactions?
2
In the first reaction, transketolase transfers 2 carbon units from xylulose-5-phosphate to?
Ribose-5-phosphate
The products of the first transketolase-catalyzed reaction are?
Glyceraldehyde-3-phosphate
Sedoheptulose-7-phospate
In the second reaction, 2 carbon units are transferred from another xylulose-5-phosphate to?
Erythrose-4-phosphate
The products of the second transketolase-catalyzed reaction are?
Glyceraldehyde-3-phosphate
Fructose-6-phosphate
The coenzyme form of thiamine is?
Thiamine pyrophosphate (TPP)
An enzyme that transfers three-carbon units from a ketose to an aldose is called?
Transaldolase
In the reaction catalyzed by transaldolase, 3 carbon units are transferred from sedoheptulose-7-phospate to?
Glyceraldehyde-3-phosphate
The products formed from the transaldolase-catalyzed reaction are?
Fructose-6-phosphate
Erythrose-4-phosphate
The result of the non-oxidative phase of the reaction pathway is the synthesis of?
Ribose-5-phosphate
Glyceraldehyde-3-phosphate (G3P)
Fructose-6-phosphate(F6P)
The glycolytic intermediates are?
Glyceraldehyde-3-phosphate (G3P)
Fructose-6-phosphate(F6P)
The function of Ribose-5-phosphate is?
Nucleotide and nucleic acid synthesis
The function of the glycolytic intermediates is?
Glycolysis
The reaction for the oxidative phase is?
Glucose-6-phosphate + 2NADP+ +H20> ribose-5-phosphate + CO2 + 2NADPH +2H+
The reaction for the non-oxidative phase is
6glucose-6-phosphate + 12NADP+ + 6H20> 5glucose-6-phosphate + 12NADPH + 12H+ +6CO2
Four functions of PPP are?
Production of NADPH for biosynthesis
Formation of ribose-5-phosphate for nucleic acid biosynthesis
A route for the conversion of pentoses to F6P and G3P
Reduces glutathione to maintain RBC membrane integrity
The most common inborn error of PPP occurs at the?
Oxidative phase of reaction pathway
An x-linked recessive hereditary genetic disorder which leads to abnormal low levels of G6PD in the cell is?
G6PD deficiency
G6PD deficiency affects mainly?
RBCs
G6PD deficiency causes RBCs to break down prematurely in a process called?
Hemolysis
The medical condition associated with G6PD deficiency is called?
Hemolytic anemia
Hemolytic anemia is common in?
Africans
Areas where malaria is endemic
Hemolytic anemia is caused by?
Lipid peroxidation
The process by which free radicals “steal” electrons from the lipids in cell membranes, resulting in cell damage is called?
Lipid peroxidation
G6PD prevents oxidative cellular damage by?
Providing substrates
G6PD is an enzyme found in the ____ of all cells in the body
Cytoplasm
Five symptoms of hemolytic anaemia are?
Shortness of breath Paleness Muscle pain Fainting and fatigue Rapid heart rate etc
Five triggering agents of hemolytic anemia in people with G6PD deficiency are?
Certain antimalarial drugs eg chloroquine
Certain chemicals eg naphthalene
Analgesics eg aspirin
Infections
Some antibiotics eg sulfonamides & non-sulfur antibiotics
An example of sulfonamides is?
Sulfamethoxazole
Examples of non-sulfur antibiotics are?
Nalidixic acid
Dapsone
Isoniazid
Fava beans or broad beans cause hemolytic anemia through?
Favism
A hereditary disorder involving an allergic-like reaction to the broad, or fava, bean
Favism
Fava beans contain the compounds vicine and convicine which are ____ agents
Oxidizing
vicine and convicine reduce the RBC____
Cell wall
Four lab diagnosis of hemolytic anemia are?
Haptoglobin estimation
Butler fluorescence test
Lactate dehydrogenase I test
Complete blood count to know the number of RBC
Inclusions within red blood cells composed of denatured hemoglobin are called?
Heinz bodies or Heinz-Ehrlich bodies
An abnormally shaped mature red blood cell with one or more semicircular portions removed from the cell margin is called?
A degmacyte or bite cell
Treatments for hemolytic anemia include
blood transfusions
medicines
plasmapheresis surgery
blood and marrow stem cell transplants and lifestyle changes