Metabolism VI

Question 1

Is the nonoxidative reaction of the HMP shunt reversible or irreversible?

Answer 1

Reversible (p.103)

Question 2

Describe the nonoxidative reaction in the HMP shunt.

Answer 2

Ribulose-5-P is converted to Ribose-5-Phosphate by phosphopentose isomerase and transketolases (p.103)

Question 3

What cofactor is required by transketolases?

Answer 3

Vitamin B1 (p.103)

Question 4

What must be activated for the oxidative burst to occur?

Answer 4

Membrane bound NADPH oxidase in neutrophlis, monocytes, etc. must be activated (p.103)

Question 5

What is the role of the oxidative burst?

Answer 5

Role in immune response causing a rapid release of reactive oxygen intermediates.

Question 6

What important cofactor contributes to the creation of ROIs (reactive oxygen intermediates) and their neutralization?

Answer 6

NADPH (p.103)

Question 7

What condition is characterized by a deficiency in NADPH oxidase?

Answer 7

Chronic Granulomatous disease (p.103)

Question 8

What characteristics are unique to the WBCs in a patient with Chronic Granulomatous disease?

Answer 8

WBCs can utilize H2O2 generated by invading organisms and convert this to ROIs (p.103)

Question 9

Why are patients with Chronic Granulomatous Disease at risk for infection?

Answer 9

Because they neutralize their own H2O2 which leaves their WBCs without the appropriate ROIs to fight infection by catalase positive species (p.103)

Question 10

Name two common catalase positive organisms.

Answer 10

S. Aureus, Aspergillus (p.103)

Question 11

Describe the pathology associated with a deficiency in Glucose-6-phosphate dehydrogenase.

Answer 11

Decreased NADPH in RBCs leads to hemolytic anemia due to poor RBC defense against oxidizing agents. Infection can also precipitate hemolysis as free radicals are generated by the inflammatory response and diffuse into RBCs to cause oxidative damage (p.104)

Question 12

Describe the role of NADPH in detoxification of free radicals.

Answer 12

NADPH keeps glutathione reduced which detoxifies free radicals and peroxides (p.104)

Question 13

Name four stereotypical oxidizing agents.

Answer 13

Fava beans, sulfonamides, primaquine, antituberculosis drugs (p.104)

Question 14

Describe the inheritance of G6PD deficiency.

Answer 14

X-linked recessive disorder. It is the most common human enzyme deficiency and is more prevalant in blacks (mutation increases malaria resistance) (p.104)

Question 15

What two cell types are seen on a blood smear of a patient with G6PD deficiency?

Answer 15

Heinz bodies, bite cells (p.104)

Question 16

What are Heinz bodies?

Answer 16

Oxidized hemoglobin precipitated within RBCs (p.104)

Question 17

What are bite cells?

Answer 17

Result from phagocytic removal of heinz bodies by splenic macrophages (p.104)

Question 18

What are the two most common disorders of fructose metabolism?

Answer 18

Essential fructosuria and fructose intolerance (p.104)

Question 19

What enzyme is deficient in essential fructosuria?

Answer 19

Defect in fructokinase (p.104)

Question 20

What enzyme is deficient in fructose intolerance?

Answer 20

Hereditary deficiency in Adolase B (p.104)

Question 21

What is the inheritance pattern associated with essential fructosuria and fructose intolerance?

Answer 21

Autosomal recessive (p.104)

Question 22

What are the symptoms of essential fructosuria?

Answer 22

It is a benign, asymptomatic condition (fructose is not trapped in cells) where fructose appears in the blood and urine (p.104)

Question 23

What are the symptoms of fructose intolerance?

Answer 23

Hypoglycemia, jaundice, cirrhosis, vomiting (p.104)

Question 24

What is the pathology of fructose intolerance?

Answer 24

Accumulation of fructose-1-phosphate causing a decrease in available phosphate which results in inhibition of glycogenolysis and gluconeogenesis (p.104)

Question 25

What is the treatment for fructose intolerance?

Answer 25

Decrease intake of both fructose and sucrose (glucose + fructose) (p.104)