PPP

Question 1

What is NADPH used for in the PPP?

Answer 1

• fatty acid synthesis
• cholesterol synthesis
• ROS protection

Question 2

What is the rate limiting step of the PPP?

Answer 2

glucose-6 phos -> G6P dehydrogenase -> ribose 5 phos

Question 3

In the PPP, what is used to go into glycolysis?

Answer 3

GA3P & F6P

Question 4

What is the location of the PPP?

Answer 4

cytosol

Question 5

What is the rate limiting enzyme of the PPP?

Answer 5

glucose-6-phosphate dehydrogenase

Question 6

What is the net energy production of PPP?

Answer 6

2 NADPH

Question 7

What is the purpose of the oxidative phase in PPP?

Answer 7

• increase NADPH
• increase ribose-5-phosphate

Question 8

What is the function of the nonoxidative phase in the PPP?

Answer 8

1. carbon shuffling
2. make ribose 5 phase WITHOUT NADPH production
3. glycolytic intermediates

Question 9

In PPP, there are 4 different modes to make what?

Answer 9

• ribose 5 phos
• NADPH
• ATP

Question 10

What is the function of glutathione?

Answer 10

to protect against ROS/oxidative stress

Question 11

What is needed to convert ROS into water?

Answer 11

GSH

Question 12

GSH peroxidase requires what to catalyze GSH -> GSSH with reduction of H2O2?

Answer 12

selenocysteine

Question 13

What is G6P dehydrogenase deficiency?

Answer 13

• X linked recessive
• causes hemolytic anemia & jaundice
• protects against malaria
• decreases NADPH= increase oxidative stress
• drug insensitivity

Question 14

How does cancer increase DNA synthesis as a PPP associated disease?

Answer 14

• cancer cells phosphorylate PEP to block glycolysis at pyruvate kinase step
• intermediates diverted into PPP
• increase PPP= increase ribose & DNA synthesis
• increase tumor proliferation

Question 15

How do tumor cells increase PPP?

Answer 15

• express embryonic M2-PK instead of adult PK
• M2-PK decreases substrate affinity
• last step of glycolysis is locked
• intermediates go to PPP-> increase PPP

Question 16

How does the Warburg effect increase glycolysis?

Answer 16

with decreased ATP production

Question 17

What is the effect of cancer cells on NADPH and ROS?

Answer 17

increases both

Question 18

What happens if there is an overexpression of GLUT1?

Answer 18

• increased glucose uptake
• GLUT1= gluconeogenesis (liver)
• GLUT2= glycolysis (pancreas)

Question 19

Tumors decrease large amounts of lactate due to what?

Answer 19

• increased LDH
• increased Gln breakdown to pyruvate
• increased Ala breakdown to pyruvate

Question 20

What are the hallmarks of tumor metabolism?

Answer 20

1. increase glucose uptake due to overexpression of GLUT1
2. increased gluconeogenesis of liver
3. express M@-PK
4. increased PPP= increased ribose & NADPH
5. large amount of lactate

Question 21

What is the composition of sucrose & galactose?

Answer 21

• sucrose = glucose + fructose
• galactose = glucose + lactose

Question 22

Why is fructose not regulated when it enters glycolysis?

Answer 22

skips rate limiting step

Question 23

What are the characteristics of hereditary fructose intolerance?

Answer 23

• mutation in aldolase B
• phosphate trapped as F-1-P
• increase in F-1-P & F-1,6,BP inhibits glycogen breakdown results in fructose-induced hypoglycemia

Question 24

What causes cataracts & mental retardation in the galactose pathway?

Answer 24

• galactitol & sorbitol -> cataracts
• galactose 1-P -> mental retardation

Question 25

What is non-classical galactosemia in the galactose pathway?

Answer 25

• galactose -> galactokinase -> galactose 1-P
• buildup of galactitol

Question 26

What is classical galactosemia in the galactose pathway?

Answer 26

• galactose 1-P -> galactose 1-P uridyltransferase -> glucose 1-P
• buildup of galactose 1-P & glactitol

Question 27

What activates sugars in the lactose pathway?

Answer 27

UDP

Question 28

What is the enzyme between UDP-glucose & UDP galactose in the lactose pathway?

Answer 28

epimerase

Question 29

What enzyme requires thiamine pyrophosphate (Vit B) in the PPP?

Answer 29

transketolase