Biochem - Metabolism (Part 2) Flashcards Preview

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Flashcards in Biochem - Metabolism (Part 2) Deck (200)
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1

Where in the cell is the enzyme glucose-6-phosphatase found?

Endoplasmic reticulum

2

In which tissues are the enzymes of gluconeogenesis found?

Liver, kidney, and intestinal epithelium

3

What product of the pentose phosphate pathway (hexose monophosphate shunt) facilitates steroid and fatty acid synthesis?

NADPH

4

What is the function of NADPH in the erythrocyte?

It reduces glutathione

5

What are the two phases of the hexose monophosphate shunt (pentose phosphate pathway)?

Irreversible oxidative phase and reversible nonoxidative phase

6

What key enzyme regulates the oxidative phase of the hexose monophosphate shunt?

Glucose-6-phosphate dehydrogenase

7

How many adenosine triphosphate molecules are used and produced by the hexose monophosphate shunt (pentose phosphate pathway)?

Zero

8

What vitamin is required for the nonoxidative phase of the hexose monophosphate shunt?

The transketolases that catalyze the nonoxidative reactions require thiamine (vitamin B1) as a cofactor

9

What four products are formed after both phases of the hexose monophosphate shunt?

Ribose-5-phosphate, G3P, F6P, and NADPH are the products

10

Which product of the hexose monophosphate shunt is used in nucleotide synthesis?

Ribose-5-phosphate

11

How are G3P and F6P utilized in the cell following the hexose monophosphate shunt?

These are glycolytic intermediates and can enter glycolysis

12

Name three sites of fatty acid or steroid synthesis that show high pentose phosphate pathway (hexose monophosphate shunt) activity.

Lactating mammary glands, liver, adrenal cortex

13

Do the reactions of the hexose monophosphate shunt (pentose phosphate pathway) take place in the mitochondria or the cytosol of a cell?

The cytosol

14

Where would you find elevated activity of the pentose phosphate pathway, but no fatty acid or steroid synthesis?

In the red blood cells; the reducing equivalents formed are necessary to neutralize oxidative radicals

15

Name two cells that utilize NADPH for an oxidative burst.

Neutrophils, macrophages

16

During the oxygen-dependent respiratory burst used by neutrophils to destroy bacteria, what enzyme converts hydrogen peroxide to bleach (hypochlorite) in the presence of chloride ion?

Myeloperoxidase, which is found in neutrophil azurophilic granules

17

Why would you expect cells like neutrophils and macrophages to have high concentrations of NADPH oxidase?

It is important for the immune response, rapidly releasing reactive oxygen species to kill bacteria

18

What disease is caused by a deficiency of NADPH oxidase?

Chronic granulomatous disease; a genetic immunodeficiency

19

During the oxygen-dependent respiratory burst that is used by neutrophils to destroy bacteria, what enzyme converts oxygen to superoxide?

NADPH oxidase

20

Which form of glutathione must be readily available in the cell to remove reactive oxygen species to prevent cell lysis?

The reduced form (GSH); reducing equivalents are created in the hexose monophosphate shunt

21

Is glutathione reduced or oxidized when converting hydrogen peroxide to water in neutrophils?

Oxidized

22

Regarding the neutrophil oxygen-dependent respiratory burst, which electron carrier is used to reduce glutathione after the conversion of hydrogen peroxide to water?

NADPH

23

During the oxygen-dependent respiratory burst that is used by neutrophils to destroy bacteria, what enzyme converts superoxide to hydrogen peroxide?

Superoxide dismutase

24

During the oxygen-dependent respiratory burst that is used by neutrophils to destroy bacteria, what enzyme converts hydrogen peroxide to water in the presence of glutathione?

Catalase

25

What enzyme uses NADPH to replenish reduced glutathione?

Glutathione reductase

26

What enzyme replenishes the NADPH used to reduce glutathione?

Glucose-6-phosphate dehydrogenase

27

What is the end product of the oxygen-dependent respiratory burst that is used to kill bacteria in the phagolysosome?

Bleach (HOCl, hypochlorite)

28

True or False? The white blood cells of patients with chronic granulomatous disease can utilize hydrogen peroxide generated by invading organisms and convert it to reactive oxygen intermediates.

True

29

Patients with chronic granulomatous disease are at an increased risk for infection by which microorganisms?

Catalase-positive species like Staphylococcus aureus and Aspergillus

30

What substance detoxifies free radicals and peroxides in the cell?

Glutathione