Pentose Phosphate Pathway (complete) Flashcards
In what cells does the pentose phosphate pathway occur
all cells
where in all cells does the pentose phosphate pathway occur
the cytoplasm
What are the two branches of the pentose phosphate pathway
- Oxidative Branch
2. Non Oxidative Branch
What is the purpose of the pentose phosphate pathway
- Production of NADPH
2. Production of Ribose-5-phosphate
What does NADPH do
- used in fatty acid synthesis
- used in steroid synthesis
- transformation of xenobiotics
- reduction of oxidized glutathione
What does Ribose-5-Phosphate do
Nucleotide synthesis (provides the sugar and phosphate portions of a nucleotide)
From which intermediate in glycolysis does the oxidative branch of the pentose phosphate pathway branch off
Glucose-6-phosphate
What is the initial enzyme used in the oxidative branch of the pentose phosphate pathway
Glucose-6-P dehydrogenase
How Many NADPH are formed in the oxidative branch of the pentose phosphate pathway
2
How many Ribose 5 phosphate are formed from the oxidative branch of the pentose phosphate pathway
1
What regulates the activity of Glucose-6-Phosphate dehydrogenase (G6PDH)
NADPH
High levels of NADPH inactivate G6PDH
Of the four reactions in the oxidative branch of the pentose phosphate pathway how many are irreversable
3 of the 4 are irreversable (first 3)
Does NADPH mostly exist as NADPH or NADP+
NADPH
NADPH:NADP+ (100:1)
Does NADH mostly exist as NADH or NAD+
NAD+
NADH:NAD+ (1;100)
What vitamins are necessary for the synthesis of NADPH
Niacin and Vitamin B3
In our lecture what was the most emphasized role of NADPH
the reduction of oxidized glutathione
What does the reduction of oxidized glutathione allow glutathione to do
reduced glutathione can turn reactive oxygen species into water.
What is the problem with having reactive oxygen species in our cells
they can damage membranes, proteins, and DNA
What is the enzyme with the glutathione that NADPH will reduce
Glutathione peroxidase
how does the reduction of oxidized glutathione work
- Oxidized glutathione is reduced by NADPH
- Reduced glutathione turns the reactive oxygen species into water. (glutathione becomes oxidized)
- Another NADPH comes and reduces the oxidized glutathione again so it can turn another reactive oxygen species into water
The deficiency of what enzyme in the body is the most common in humans
G6PDH deficiency
What does G6PDH deficiency lead to in terms of
NADPH and GSH
low levels of NADPH
Low levels of GSH (reduced glutathione)
What is GSH
reduced glutathione
What is G-S-S-G
oxidized glutathione
What are two effects of G6DPH deficiency
- Malaria resistance
2. Hemolytic Anemia
What cells are most affected by G6PDH deficiency
erythrocytes
What is hemolytic anemia
Too many red blood cells dying, so the person becomes anemic
What causes someone with G6PDH deficiency to get hemolytic anemia
Low NADPH = Low GSH = high amounts of reactive oxygen species
From what sources can a person get the peroxide forming substances that can lead to anemia
Primaquine
Sulfonamide
Fava beans
Which of the two effects of G6PDH deficiency can be a good side effect
Malaria resistance
how does G6PDH deficiency lead to Malaria resistance
the erthyrocytes become altered, which makes them resistant to malaria
From where in glycolysis does the non-oxidative branch of the pentose phosphate pathway break off
- from fructose-6-phosphate
2. from one of the splitting intermediates after the splitting phase
Is the non-oxidative branch of the pentose phosphate pathway reversable
yes. to both the frucotse 6 phosphate and the splitting intermediate
what is the product of the non-oxidative branch of the pentose phosphate pathwya
ribose-5-phosphate
Why is it significant that the non-oxidative branch of the pentose phosphate pathway is reversable
because the excess ribose-5-phosphate produced by both the non-oxidative and oxidative branches can be returned to the glycolysis/gluconeogenesis pathway.
How many Ribose-5-Phosphates do you need to reverse the non-oxidative branch of the pentose phosphate pathway, and how many of each of the products do you get from those ribose-5-phosphates
3 ribose-5-phosphates are needed to reverse the non-oxidative branch. 2 fructose-6-phosphates and 1 splitting intermediate is formed.
What are the main differences between the oxidative and non oxidative branches
the oxidative branch produces NADPH and ISN’T reversable
The non-oxidative branch DOESN’T produce NADPH and IS reversable
What is the main similarity between the oxidative and non-oxidative branches
they both produce Ribose-5-Phosphate
Which branch produces CO2
the oxidative branch
What is the enzyme that reduces Oxidized glutathione back to reduced glutathione, and uses NADPH as a cofactor
Glutathione reductase
