Final: pentose phosphate pathway

Question 1

glucose-6-phosphate has 2 fates

Answer 1

1) glycolysis to make ATP

2) pentose phosphate pathway

Question 2

pentose phosphate pathway

Answer 2

name tells us its products
pentose = 5 carbon sugar (ribose)
phosphate = NADPH

Question 3

when do we use PPP?

Answer 3

when cells need ribose or NADPH

OR to interconvert sugars

Question 4

what do we use ribose for

Answer 4

ribose makes nucleotides

Question 5

what do we use NADPH for

Answer 5

• it is rich in electrons
• useful in various anabolic pathways
• synthesizing fatty acids
• NADPH is an electron donor
• provides reducing power

Question 6

where does PPP occur?

Answer 6

cytoplasm
requires no Oxygen
all cells can use PPP

Question 7

PPP 2 phases

Answer 7

1) irreversible oxidative phase yields NADPH

2) reversible non-oxidative phase yields Ribose

Question 8

oxidation

Answer 8

donates or loses H+ to another molecule

Question 9

rate limiting step of oxidative PPP

Answer 9

step 1: glucose-6-phosphate to 6-phosphogluconate

enzyme: glucose-6-phosphate dehydrogenase (G6PD)

Question 10

oxidative phase step 1

Answer 10

1) glucose-6-phosphate to 6-phosphogluconate (NADP+ to NADPH)
enzyme: glucose-6-phosphate dehydrogenase (G6PD)

Question 11

oxidative phase products

Answer 11

2 NADPH per 1 glucose

Question 12

why do we want ribose-5-phosphate?

Answer 12

it can be the 5 carbon sugar for DNA/RNA synthesis

Question 13

what else can ribulose-5-phosphate become?

Answer 13

xylulose-5-phosphate

if cell doesn’t need to make nucleotides, we can use xylulose to make glycolysis intermediates (G3P and F6P)

Question 14

what happens if cell wants more energy midway through PPP?

Answer 14

it can divert to glycolysis by creating glycolysis intermediates!

it can also do the same if it is mid glycolysis and wants to switch to PPP