Pentose Phosphate Pathway

Question 1

Pentose phosphate pathway (PPP) is not designed to

Answer 1

not designed to produce energy (it can produce energy, but its not designed to

Question 2

PPP allows the production of what 2 things

Answer 2

1. 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).
2. Ribose-5-phosphate: This sugar is essential to nucleic acid synthesis or some co-enzymes.

Question 3

PPP is mainly active in

Answer 3

1. 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.
2. Adipose tissue: fatty acid synthesis
3. Mammary gland: fatty acid synthesis
4. Steroidogenic tissues: Steroid hormone production.
5. Red blood cells: Repair of oxidative damage

Question 4

The starting substrate of PPP is

Answer 4

Glucose-6-phosphate (same as the product produced after reaction 1 of glycolysis)

Question 5

In the liver glucose-6-phosphate is generated by

Answer 5

glucokinase (Hexokinase IV)

Question 6

Glucokinase is dependent on

Answer 6

Glucose concentration in the liver

Question 7

Glucokinase is not inhibited by

Answer 7

G6P (glucose-6-phosphate) like in the muscle

Question 8

Both PPP and glycolysis occur when there is a surplus of

Answer 8

glucose

Question 9

what are the 2 phases of PPP

Answer 9

1. Oxidative (Reduction of NADP+
2. Non-oxidative

Question 10

Pentose phosphate pathway mechanism

Answer 10

Oxidative phase going from G6P (glucose 6-phosphate) to ribulose 5-phosphate (oxidative = NADP+ converted to NADPH)

Question 11

Oxidative phase of PPP generates

Answer 11

2 NADPH and 1 D-Ribulose 5-phosphate/D-ribose 5-phosphate

Question 12

T or F: During oxidative phase of PPP there is a decarboxylation when going from glucose 6-phosphate to ribose-5-phosphate

Answer 12

True

Question 13

Oxidative phase of PPP

Answer 13

Question 14

Non-oxidative phase of PPP

Answer 14

NOTE: Can create a loop to produce NADPH over and over again

Question 15

How many ribose 5-phosphate does it take to produce 5 glucose

Answer 15

**these enzymes are found in glycolysis and gluconeogenesis (remember this pathway)

6 ribose 5-phosphate can produce 5 glucose

Question 16

T or F: PPP cannot be used to generate energy

Answer 16

False, it can

Question 17

What are the 4 fates of G6P according to their cellular needs

Answer 17

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

Question 18

Situation 1: Cell needs BOTH ribose-5-phosphate and NADPH

Answer 18

Question 19

Situation 2: Cell needs MORE NAPDH than ribose-5-phosphate

Answer 19

Question 20

Situation 3: Cell needs NADPH and ATP

Answer 20

Question 21

Situation 4: Cell needs ONLY ribose-5-phosphate

Answer 21

**The PPP pathway is reversible so can go backwards to produce ribose 5-phosphate