Pentose Phosphate Pathway Flashcards
Pentose phosphate pathway (PPP) is not designed to
not designed to produce energy (it can produce energy, but its not designed to
PPP allows the production of what 2 things
- NADPH: This coenzyme is necessary to certain synthesis reactions requiring reducing steps (ex: fatty acid, cholesterol, steroid synthesis) and other reducing reactions (ex. Repair oxidative damage).
- Ribose-5-phosphate: This sugar is essential to nucleic acid synthesis or some co-enzymes.
PPP is mainly active in
- Liver :allows the synthesis of fatty acids and cholesterol. The activity of the pentose phosphate pathway in the liver is greater than that of glycolysis, since β-oxidation of lipids generates most of the energy in this organ.
- Adipose tissue: fatty acid synthesis
- Mammary gland: fatty acid synthesis
- Steroidogenic tissues: Steroid hormone production.
- Red blood cells: Repair of oxidative damage
The starting substrate of PPP is
Glucose-6-phosphate (same as the product produced after reaction 1 of glycolysis)
In the liver glucose-6-phosphate is generated by
glucokinase (Hexokinase IV)
Glucokinase is dependent on
Glucose concentration in the liver
Glucokinase is not inhibited by
G6P (glucose-6-phosphate) like in the muscle
Both PPP and glycolysis occur when there is a surplus of
glucose
what are the 2 phases of PPP
- Oxidative (Reduction of NADP+
- Non-oxidative
Pentose phosphate pathway mechanism
Oxidative phase going from G6P (glucose 6-phosphate) to ribulose 5-phosphate (oxidative = NADP+ converted to NADPH)
Oxidative phase of PPP generates
2 NADPH and 1 D-Ribulose 5-phosphate/D-ribose 5-phosphate
T or F: During oxidative phase of PPP there is a decarboxylation when going from glucose 6-phosphate to ribose-5-phosphate
True
Oxidative phase of PPP
Non-oxidative phase of PPP
NOTE: Can create a loop to produce NADPH over and over again
How many ribose 5-phosphate does it take to produce 5 glucose
**these enzymes are found in glycolysis and gluconeogenesis (remember this pathway)
6 ribose 5-phosphate can produce 5 glucose
T or F: PPP cannot be used to generate energy
False, it can
What are the 4 fates of G6P according to their cellular needs
Situation 1. Cell needs BOTH ribose 5-phosphate and NADPH
Situation 2. Cell needs MORE NADPH than ribose 5-phosphate
Situation 3. Cell needs NAPDH and ATP
Situation 4. Cell needs ONLY ribose 5-phosphate
Situation 1: Cell needs BOTH ribose-5-phosphate and NADPH
Situation 2: Cell needs MORE NAPDH than ribose-5-phosphate
Situation 3: Cell needs NADPH and ATP
Situation 4: Cell needs ONLY ribose-5-phosphate
**The PPP pathway is reversible so can go backwards to produce ribose 5-phosphate
