4. PPP

Question 1

3 fates of glucose in mammalian cells:

Answer 1

• Storage as glycogen, starch, sucrose

Question 2

But we also synthesize our own nucleic acids and amino acids using ____________ ____________

Answer 2

reducing power

Question 3

Why is NADH not a good reducing agent for reducing power?

Answer 3

NAD+/NADH ratio is always around 1000 (i.e. high concentrations of NAD+). Therefore NADH is not the best reducing equivalent for synthetic reaction. Our mitochondrial is so efficient that as soon as it is produced, it very quickly gets converted to NAD+

Question 4

What is the solution to NADH not being good for reducing power in synthetic reactions?

Answer 4

NADPH:

Question 5

PPP overall reaction:

Answer 5

The overall reaction:

Question 6

This pathway also leads to the formation of pentose sugar intermediates such as Ribose 5 phosphate, Ribulose 5 phosphate that are essential for nucleic acid synthesis. True or false?

Answer 6

TRUE

Question 7

There are seven enzymes involved in three different steps of this pathway:

Answer 7

1.Oxidative reactions:

Question 8

3 carbon molecules from the G6P are oxidized to produce 3______

Answer 8

CO2

Question 9

Provide the oxidative phase of PPP pathway:

Answer 9

• g6p and NADP+ to form 6-phosphogluconolactone and NADPH via G6PDH (oxidation #1)

Question 10

The hydrogens taken out in the 2 oxidations of the oxidation phase of PPP are in what form?

Answer 10

hydride

Question 11

Provide the isomerization and epimerization reactions of PPP and what happens specifically in the conversions:

Answer 11

Ru5P to R5P via ribulose-5-phosphate isomerase –>

Question 12

Provide the transketolase and transaldolase reactions in PPP:

Answer 12

• 2C from Xu5P + r5p produces S7P by transketolase

Question 13

What is the purpose of the transketolase and transaldolase reacttions in PPP?

Answer 13

if u don’t need R5P, but you still want to form NADPH for REDUCING POWER, u can recycle back to GAP and F6P to enter glycolysis (synthesizes glycolysis intermediates) –> make only what you need

Question 14

What are the 2 major products of PPP and explain:

Answer 14

The major specific product of this pathway are NADPH and Ribose 5P which are used as reducing power for synthetic reactions and nucleic acid synthesis, respectively.

Question 15

What is the main enzyme that controls the flux (overall rate) of this pathway?

Answer 15

G6PDH

Question 16

Explain PPP regulation besides reactant and product concentration:

Answer 16

G6P DH is strongly inhibited by NADPH. Thus if the NADPH concentration decreases, the G6PDH is activated.

Question 17

What are the 2 major functions of NADPH:

Answer 17

• Reducing power for reactions

Question 18

Role of NADPH in reducing oxidative stress:

Answer 18

NADPH is used to generate reduced glutathione (GSH). GSH plays a critical role in quenching the oxyradicals in the cells.

Question 19

If NADPH generation is inhibited due to the mutations in ___________, cells become susceptible to oxidative damage.

Answer 19

g6pdh

Question 20

What are the 3 types of ROS?

Answer 20

Superoxide radical, hydrogen peroxide, and hydroxyl radical

Question 21

Describe how NADPH is involved in quenching oxyradicals in cells:

Answer 21

Reduced glutathione (GSH) is used to block hydroxyl free radical from oxidative damage to lipids, proteins, and DNA.

Question 22

Why are G6PDH deficient individuals resistant to malaria?

Answer 22

Malaria parasite is very sensitive to Oxy-radicals, and people with G6PDH defect are resistant to malaria as the parasite is killed by oxy-radicals. This is bc these people have higher amount of ROS in their blood.