Hexose Monophosphate Pathway Flashcards
Where in the cell does the hexose monophosphate pathway (also known as: pentose phosphate pathway) occur?
Cytoplasm
What is the major product of the oxidative pathway?
What is the major product of BOTH pathways?
- Main product of oxidative pathway = NADPH
- Main product of both pathways = Ribose
True or False: The hexose monophosphate pathway produces ATP
False - it does NOT
Which pathway generates NADP and 5 carbon monosaccharides?
Oxidative Pathway
Overall reaction of the oxidative pathway?
Reactant: Glucose-6-Pi + 2NADP+ and water
Product: Ribose-5-Pi + CO2 + 2 NADPH + H+
What enzyme is involved in the committed, irreversible step of the oxidative pathway?
Glucose 5 phosphate dehydrogenase
What is the committed, irreversible step of the oxidative pathway? Product?
Glucose-6-phosphate -> 6-phosphoglucono-delta-lactone
(NADP+ -> NADPH)
Which enzyme in oxidative pathway produces and is inhibited by NADPH?
Glucose-6-phosphate dehydrogenase
In the second step of the oxidative pathway, _____ is converted to ______ using _____ (also known as glucanolactonase).
What is consumed in reaction?
6-phosphoglucono-delta-lactone ->
6-phosphogluconate
Enzyme: 6-phosphogluconolactone hydrolase
1 water molecule is consumed
How many steps in the oxidative pathway are reversible? Irreversible?
Reversible - 2 (including isomerase reaction)
Irreversible - 2
At what stages of the oxidative pathway is NADPH generated?
Step 1 and Step 3
Third step of the oxidative pathway?
Products?
6 phosphogluconate -> ribulose-5-Pi + CO2
Enzyme: 6-phosphogluconoate dehydrogenase
Products: CO2 + NADPH
In the 4th step of the oxidative pathway,
ribulose 5-phosphate is interconverted between ribose-5-phosphate using which enzyme?
Is this stage irreversible or reversible?
Isomerase
- Reversible
_____ is an isomer that is important for DNA synthesis
ribose-5-phosphate
____is an important isomer for the body and is created in the final stage of the oxidative pathway
xyulose-5-phosphate
In the final stage of the oxidative pathway, ___ is converted to ____
What enzyme is required?
ribulose-5-phosphate <-> xyulose-5-P
Epimeriase
The ratio of _____:____ regulates the committed step of the oxidative pathway
NADPH/NADP+
When the cell needs more NADPH, the ratio of ___ decreases and flux through pathway ___
decreases; increases
How does insulin affect expression of G6PD gene in the liver? How does it affect flux through the pathway after a meal?
Insulin upregulates the expression of G6PD in the liver
Increases flux through pathway after a meal
What organ is the major site of fatty acid biosynthesis?
Liver
Which pathway makes 5C monosaccharide (ribose) withouts without making NADPH?
Non-Oxidative pathway
True or False: The Non-Oxidative Branch of the pentose phosphate pathway has enzymes found in all cells that make nucleotides (note: all cells need nucleotides, such as ATP, to some extent)
True
In the Non-Oxidative Pathway ___ is converted to ___ and ____
3-ribose-5-phosphate =>
2 fructose 6-Pi + 3-glyceraldehyde-3-Pi
The non-oxidative pathway uses three enzymes, but two key ones are ____ and ___
transketolase + transaldolase
_____ transfers 2C group and requires thiamine
____transfers 3C group
Transketolase
Transaldolase
What is the first step of the non-oxidative pathway?
Ribulose-5-P <–> xyulose-5-P
Via: phosphopentose epimerase
In step 2 of non-oxidative pathway, transketolase takes 2 carbons off of ____ and donates them to _____
What does this yield?
xyulose-5-P ; ribose-5-P
Yields: Glyceraldehyde-3-P +Seduoheptulase 7-Pi
______, a product of stage 2 (non-oxidative pathway), is a glycolysis intermediate
Glyceraldehyde-3-P
Stage 3 of the non-oxidative pathway involves _____, an enzyme, pulling 3 carbons off of ____ and adding them to ______ to yield ____+_____
Transaldolase; seduoheptulase-7-P; glyceraldehyde-3-P
= erythrose-4-P + fructose-6-Pi
____, a product of stage 3 non-oxidative pathway, is a glycolysis intermediate
fructose-6-Pi
In stage 4 of the non-oxidative pathway, ____, an enzyme, removes 2 carbons off of ___ and adds them to ___, yielding ___ and ____
Transketolase; Xyulose-5-P ; Erythrose-4-Pi
= Glyceraldehyde-3-P + Fructose-6-P (both are intermediates in glycolysis)
What two factors regulate the non-oxidative branch?
Level of substrates and needs of the cell
True or False: For the non-oxidative branch, you can make use ribose-P to make glycolytic intermediates or vice versa
True
NADPH is important for synthesis of ___, ___, and ____
fatty acids, cholesterol, steroids
True or False: Biosynthetic reactions that involve oxidation require NADPH
False - Biosynthetic reactions that involve REDUCTION require NADPH (carries 1 H+ and 2e-)
Generates NADP as a product
Biosynthetic pathways that make NADPH are found in the ____, ____, ____, ____, and ____
liver, adrenal gland, testes, ovaries
Synthesis of ___ requires NADPH
NO
L-Arginine is converted to L-Citrulline using NO Synthase and ____. As a result, ___ is made
NADPH; NO
Roles of NO?
1) Relaxes smooth muscle
2) Brain NT
3) Regulates macrophages
4) Prevents platelet aggregation
Maintaining reduced glutathione requires ____
NADPH
What three molecules make up glutathione?
1) Glycine
2) Cysteine
3) y-glutamate
GSSG = ?
GSH = ?
GSSG = oxidized glutathione
GSH = reduced glutathione
Reduced glutathione (GSH) reacts with ___ and other organic peroxides to prevent cellular damage
H2O2
- neutralizes damage potential
_____ is a good reducing agent for detoxification
Reduced glutathione
_____ GSH keeps amino acid side chains in proteins reduced. It keeps them from oxidizing and forming wrong disulfide bonds.
Sulfhydryl buffer
Glutathione Reductase is an enzyme that uses NADPH to generate ___ from ___
GSH ; GSSG
