Biochemistry Chapter 20 Questions

The KM of glucose 6-phosphate dehydrogenase for NADP+ is _____ the KM for NAD+.

1000 times lower than

How many phases are in the pentose phosphate pathway?

2

How many molecules of ATP and NADPH are consumed in the incorporation of a single CO2 molecule into a hexose?

3 ATP, 2 NADPH

How many ATP molecules are required by the C4 pathway for each hexose that is produced from CO2?

30

In the oxidative phase of the pentose phosphate pathway, transformation of 6-phosphogluconate to ribulose 5-phosphate is catalyzed by:

6-phosphogluconate dehydrogenase

In the overall equation for the Calvin cycle, three molecules of ____ and two molecules of ____ are consumed in incorporating a single CO2 molecule into a hexose.

ATP; NADPH

What pathway does NOT require extra energy to pump CO2 into the bundle sheath cells and is used by plants that are not able to grow in hot, dry climates?

C3 pathway

What pathway ensures that sufficient amounts of CO2 are available?

C4 pathway

Which of the following reactions catalyzed by transketolase does NOT coordinate the pentose phosphate pathway with glycolysis?

C5+C6 to C2+C9

Why is the C4 pathway necessary for tropical plants?

Carbon dioxide is concentrated in bundle-sheath cells, which are the major sites of photosynthesis.

Rubisco:

Catalyzes a deleterious oxygenase reaction.

What prosthetic group or enzyme does NOT take part in photorespiratory reactions?

FAD

The schiff base:

Has the structure R3C-NR'R"

Which coenzyme is required by glyceraldehyde 3-phosphate dehydrogenase in chloroplasts to convert 3-phosphoglycerate into glyceraldehyde 3-phosphate?

NADPH

Which cofactor supplies the reducing power for reduction of glutathione by glutathione reductase?

NADPH

What process is wasteful because of conversion of organic carbon into CO2 without the production of ATP, NADPH, or another energy-rich metabolite?

Photorespiration

Choose the FALSE statement concerning the activation of Calvin cycle enzymes.

Reduced thioredoxin activates several degradative enzymes

In what part of the cell does the Calvin-Benson cycle occur

Stroma of the chloroplasts

Choose the FALSE statement concerning the regulation of the pentose phosphate pathway.

The reaction of dehydrogenation of glucose 6-phosphate does not influence the rate of the whole pathway.

Choose the CORRECT statement concerning the action of transketolase and trasnsaldolase.

Transaldolase transfers a three-carbon unit.

____plays a major role in the regeneration of ribulose 1,5 bisphosphate.

Transketolase and aldolase

_________ is involved in both in the Calvin cycle and the pentose phosphate pathway.

Trasnaldolase

The source of carbon for the Calvin cycle is:

carbon dioxide

What metabolic adaptation is employed by plants living in hot, dry climates to prevent water loss and decrease photorespiration?

cassulacean acid metabolism

In what part of the cell does the pentose phosphate pathway occur?

cytoplasm

What substance does CO2 condense with to produce two molecules of 3-phosphoglycerate at the first step of the Calvin cycle

enediolate intermediate

The products in the reaction of glyceraldehyde 3-phosphate plus sedoheptulose 7-phosphate are erythrose 4-phosphate and

fructose 6-phosphate

What substance is a member of the hexose monophosphate pool?

fructose 6-phosphate

Dehydrogenation of glucose 6-phosphate at carbon 1 at the first step of the oxidative phase of the pentose phosphate pathway is catalyzed by:

glucose 6-phosphate dehydrogenase

Falciparum malaria, a disease that requires NADPH for growth, is caused by the parasite Plasmodium falciparum. The deficiency of which enzyme leads to an increase NADPH, and eventually hemolytic anemia?

glucose 6-phosphate dehydrogenase

In the oxidative phase of the pentose phosphate pathway, transformation of glucose 6-phosphate to 6-phosphoglucono-o-lactone is catalyzed by:

glucose 6-phosphate dehydrogenase

What enzymes do NOT take part in the regeneration of ribulose 1,5-bisphosphate?

glucose 6-phosphate dehydrogenase

What is NOT the name of the pathway that oxidizes glucose to carbon dioxide to generate NADPH?

glucose phosphate pathway

What thiol-containing molecule in its reduced state is critical to reducing reactive oxygen species?

glutathione

Select all that apply. The products of the first reaction linking the pentose phosphate pathway and glycolysis are:

glyceraldehyde 3-phosphate. sedoheptulose 7-phosphate.

What concentration change does NOT contribute to activation of Calvin cycle enzymes?

increase in the H+ concentration in stroma in the light reactions.

In the oxidative phase of the pentose phosphate pathway, transformation of 6-phophoglucono-o-lactone to 6-phosphogluconate is catalyzed by:

lactonase

In what organelle does glycolate transform into glycine during photorespiration?

peroxisome

Select all that apply. The formation of xylulose 5-phosphate from ribose 5-phosphate is catalyzed by:

phosphopentose isomerase hophopentose epimerase

Which form of thioredoxin activates certain Calvin cycle enzymes?

reduced

Which sugar(s) is/are converted into ribulose 5-phosphate by a single enzymatic step? Select all that apply.

ribose 5-phosphate xylulose 5-phosphate

What is the name of the enzyme that is located on the stromal surface of the thylakoid membranes and catalyzes condensation of CO2 with the endiolate intermediate?

rubisco

What enzyme uses ATP to induce structural changes in rubisco and thus coordinates rubisco activity with the light reactions?

rubisco activase

Which tissue has the least active pentose phosphate pathway?

skeletal muscle

A readily mobilized sugar that is commonly used to transport carbohydrates through a plant is:

sucrose

Which is not an additional function of the pentose phosphate pathway?

synthesis of hexose sugars for nucleotide biosynthesis

In the transketolase reaction:

the first step is the ionization of thiamine pyrophosphate.

In the transaldolase reaction:

the nitrogen atom of the protonated Schiff base plays the same role in transaldolase as the thiazole-ring nitrogen atom does in transketolase.

What prosthetic group is tightly bound to the enzyme transketolase?

thiamine pyrophosphate

The donor of the two-carbon unit in the first reaction linking the pentose phosphate pathway and glycolysis is:

xylulose 5-phosphate