Chapter 15

Question 1

What are the products of the pentose phosphate pathway?

Answer 1

Ribose-5-phosphate and NADPH

Question 2

What is ribose-5-phosphate used for?

Answer 2

Synthesis of nucleic acids

Question 3

What is the purpose of distinct active sites for NADH and NADPH?

Answer 3

Oxidation and reduction pathways occur at the same time within the cell

Question 4

Where does the pentose phosphate pathway occur?

Answer 4

Cytosol

Question 5

What is the concentration of [NAD+]/[NADH] in the cytosol?

Answer 5

[NAD+]/[NADH] = 1000

Question 6

What is the concentration of [NADP+]/[NADPH] in the cytosol?

Answer 6

[NADP+]/[NADPH] = 0.01

Question 7

Is the oxidative phase of the pentose phosphate pathway reversible? Why or why not?

Answer 7

No, unidirectional due to decarboxylation

Question 8

What is the carbon product of the oxidative phase of the pentose phosphate pathway?

Answer 8

Ribulose-5-phosphate (Ru5P)

Question 9

How many NADPH are produced during the oxidation phase of glycolysis?

Answer 9

3 G6P -> 6 NADPH (2 per G6P)

Question 10

What is the rate-limiting enzyme in the pentose phosphate pathway?

Answer 10

Glucose-6-phosphate dehydrogenase (first reaction; oxidizes G6P)

Question 11

What is a lactone?

Answer 11

Cyclic ester (ring with a C=O)

Question 12

What is the structure of G6P?

Answer 12

Hemiacetal

Question 13

What is the first reaction of the oxidative phase of the pentose phosphate pathway?

Answer 13

G6P -> 6-Phosphoglucono-delta-lactone using the enzyme G6PDH

Question 14

What is the second reaction of the oxidative phase of the pentose phosphate pathway?

Answer 14

6-Phosphoglucono-delta-lactone -> 6-Phosphogluconate using the enzyme 6PGL

Question 15

What is the third reaction of the oxidative phase of the pentose phosphate pathway?

Answer 15

6-Phosphogluconate -> Ru5P using the enzyme 6PGDH

Question 16

What is the structure of Ru5P?

Answer 16

Penta-ketose

Question 17

What is the function of glutathione?

Answer 17

Reduce peroxides to alcohol and water

Question 18

What does the body need to produce in order to deal with oxidative stress?

Answer 18

NADPH

Question 19

What are the chemical reactions that the body uses to deal with oxidative stress?

Answer 19

GSSG + NADPH -> 2 GSH + NADP+

2 GSH + ROOH -> GSSG + ROH + H2O

Question 20

What molecule(s) is Ru5P converted to after the oxidative phase of the pentose phosphate pathway?

Answer 20

R5P or Xu5P

Question 21

What enzyme is used to convert Ru5P to R5P?

Answer 21

Ribulose-5-phosphate isomerase (RPI)

Question 22

What enzyme is used to convert Ru5P to Xu5P?

Answer 22

Ribulose-5-phosphate epimerase (RuPE)

Question 23

Where does RuPE epimerize Ru5P?

Answer 23

3 carbon

Question 24

What isomerization is done to Ru5P?

Answer 24

Ru5P (ketose) to R5P (aldose)

Question 25

What is the function of transketolase?

Answer 25

2 carbon transfers

Question 26

What is the function of transaldolase?

Answer 26

3 carbon transfers

Question 27

What are the ultimate products of the C-C bond arrangement phase of the pentose phosphate pathway?

Answer 27

2x F6P (6 carbons) and 1x GAP (3 carbons)

Question 28

What happens in the breakdown of fructose in muscle tissue?

Answer 28

Converted to F6P by hexokinase and enters glycolysis

Question 29

Why can’t fructose be directly converted to F6P in the liver?

Answer 29

Hexokinase isn’t present in the liver

Question 30

What enzyme acts on fructose in the liver?

Answer 30

Fructokinase; converts to F1P

Question 31

Which enzyme forms glyceraldehyde from F1P in the liver?

Answer 31

Fructose-1-phosphate aldolase (aldolase type B)

Question 32

What enzyme converts glyceraldehyde to glycerol?

Answer 32

Alcohol dehydrogenase

Question 33

What enzyme converts glyceraldehyde to G3P?

Answer 33

Glyceraldehyde kinase

Question 34

What is glycerol used for?

Answer 34

Fatty acid synthesis

Question 35

What is glycerol-3-phosphate used for?

Answer 35

Glycerophospholipid synthesis