Chapter 26

Question 1

what is glucose 6-phosphate?

Answer 1

a substrate for the pentose phosphate pathway

Question 2

what does the pentose phosphate pathway produce?

Answer 2

NADPH

Question 3

how does the pentose phosphate pathway work?

Answer 3

it catalyzes the interconversion of 3 and 6-carbon intermediates of glycolysis with 5-carbon carbohydrates.

Question 4

where are the pentose sugars from the pentose phosphate pathway used?

Answer 4

in the synthesis of DNA and RNA

Question 5

what does the oxidative phase of the pentose phosphate pathway produce?

Answer 5

NADPH

Question 6

what does the nonoxidative phase of the pentose phosphate pathway produce?

Answer 6

sugars

Question 7

what controls the rate of the pentose phosphate pathway?

Answer 7

the level of NADP+

Question 8

what is the rate-limiting step of the pentose phosphate pathway?

Answer 8

the first reaction; the dehydration of glucose 6-phosphate by glucose 6-phosphate dehydrogenase

Question 9

what is the most important regulatory factor of the pentose phosphate pathway?

Answer 9

NADP+

Question 10

what are the four modes that the pentose phosphate pathway can operate in?

Answer 10

1. Ribose 5-phosphate needs exceed the needs for NADPH
2. The NADPH and ribose 5-phosphate needs are balanced
3. More NADPH is needed than ribose 5-phosphate
4. NADPH and ATP are both required

Question 11

what happens when the pentose phosphate pathway operates in the first mode, where Ribose 5-phosphate needs exceed the needs for NADPH?

Answer 11

Rapidly dividing cells require precursors for DNA and RNA

Question 12

what happens when the pentose phosphate pathway operates in the second mode, where The NADPH and ribose 5-phosphate needs are balanced?

Answer 12

biosynthetic reducing power and nucleotide precursors are needed

Question 13

what happens when the pentose phosphate pathway operates in the third mode, where More NADPH is needed than ribose 5-phosphate?

Answer 13

NADPH is needed for fatty acid and cholesterol synthesis in the liver

Question 14

what happens when the pentose phosphate pathway operates in the fourth mode, where NADPH and ATP are both required?

Answer 14

reducing power and ATP (through pyruvate) are both needed

Question 15

what is the pentose phosphate pathway used for?

Answer 15

it produces NADPH in oxidative phase
produces ribose 5-phosphate
can feed into glycolytic pathway

Question 16

how does the oxidative phase generate NADPH?

Answer 16

NADPH is generated when glucose 6-phosphate is oxidized to ribulose 5- phosphate