Chapter 20

Question 1

The compound that condenses with CO2 in the first reaction of carbon dioxide assimilation is:

A) 3-phosphoglycerate.
B) ribose 1,5-bisphosphate.
C) ribulose 1,5-bisphosphate.
D) ribulose 5-phosphate.
E) rubisco.

Answer 1

C) ribulose 1,5-bisphosphate.

Question 2

Which of these enzymes is not part of the Calvin cycle?

A) Aldolase
B) Glyceraldehyde 3-phosphate dehydrogenase
C) Phosphofructokinase-1
D) Ribulose-5-phosphate kinase
E) Transketolase

Answer 2

C) Phosphofructokinase-1

Question 3

Transketolase requires the coenzyme:

A) cobalamin (vitamin B12).
B) lipoic acid
C) pyridoxal phosphate.
D) tetrahydrofolic acid.
E) thiamine pyrophosphate.

Answer 3

E) thiamine pyrophosphate.

Question 4

When transketolase acts on fructose 6-phosphate and glyceraldehyde 3-phosphate, the products are:

A) 3-phosphoglycerate and glyceraldehyde 3-phosphate.
B) 3-phosphoglycerate and two molecules of glyceraldehyde 3-phosphate.
C) dihydroxyacetone phosphate and glucose 6-phosphate.
D) xylulose 5-phosphate and erythrose 4-phosphate.
E) xylulose 5-phosphate and ribose 5-phosphate.

Answer 4

D) xylulose 5-phosphate and erythrose 4-phosphate.

Question 5

Which of these compounds is not directly involved in the Calvin cycle?

A) Erythrose 4-phosphate
B) Glyceraldehyde 3-phosphate
C) Mannose 6-phosphate
D) Ribulose 5-phosphate
E) Sedoheptulose 7-phosphate

Answer 5

C) Mannose 6-phosphate

Question 6

In the carbon assimilation (“dark”) reactions of photosynthesis, the biosynthesis of 1 mol of hexose
from 6 mol of carbon dioxide requires:

A) 12 mol of NADPH and 12 mol of ATP.
B) 12 mol of NADPH and 18 mol of ATP.
C) 18 mol of NADPH and 12 mol of ATP.
D) 18 mol of NADPH and 18 mol of ATP.
E) no NADPH and 12 mol of ATP.

Answer 6

B) 12 mol of NADPH and 18 mol of ATP.

Question 7

The known mechanisms of activation of rubisco or of other enzymes of the Calvin cycle during
illumination include all of the following except:

A) increased stromal pH.
B) light-driven entry of Mg2+ into the stroma.
C) phosphorylation by cAMP-dependent protein kinase.
D) phosphorylation of phosphoenolpyruvate carboxylase.
E) reduction of a disulfide bridge by thioredoxin.

Answer 7

C) phosphorylation by cAMP-dependent protein kinase.

Question 8

Which of these chloroplast enzymes is not regulated by light?

A) Fructose 1,6-bisphosphatase
B) Glyceraldehyde-phosphate dehydrogenase
C) Ribulose 5-phosphate kinase
D) Sedoheptulose 1,7-bisphosphatase
E) All of the above are regulated by light.

Answer 8

E) All of the above are regulated by light.

Question 9

The carbon assimilation (“dark”) reactions of photosynthetic plants:

A) are driven ultimately by the energy of sunlight.
B) are important to plants, but ultimately of little significance for bacteria and animals.
C) cannot occur in the light.
D) yield (reduced) NADH.
E) yield ATP, which is required for the light reactions

Answer 9

A) are driven ultimately by the energy of sunlight.

Question 10

The assimilation of CO2 into organic compounds (triose phosphates) in green plants:

A) involves condensation of the two-carbon compound acetate with CO2 to form 3-phosphoglycerate.
B) requires NADPH.
C) results in the production of ATP.
D) takes place at equal rates in light and darkness.
E) takes place in the cytosol.

Answer 10

B) requires NADPH.

Question 11

All are true of photorespiration except:

A) It is driven by light.
B) It oxidizes substrates to CO2.
C) It produces O2.
D) It results from a lack of specificity of the enzyme rubisco.
E) It results in no fixation of carbon.

Answer 11

C) It produces O2.

Question 12

The three subcellular organelles involved in the phosphoglycolate salvage pathway are:

A) endoplasmic reticulum, chloroplast, and mitochondrion.
B) nucleus, endoplasmic reticulum, and chloroplast.
C) golgi apparatus, chloroplast, and mitochondrion.
D) mitochondrion, peroxisome, and chloroplast.
E) peroxisome, endoplasmic reticulum, and chloroplast

Answer 12

D) mitochondrion, peroxisome, and chloroplast.

Question 13

The glycine decarboxylase complex in the leaves of pea or spinach plants is localized mainly in the:

A) chloroplast.
B) endoplasmic reticulum.
C) mitochondrion.
D) cell membrane.
E) peroxisome.

Answer 13

C) mitochondrion.

Question 14

In “C4” plants of tropical origin, the first intermediate into which 14CO2 is fixed is:

A) aspartate.
B) phosphoenolpyruvate.
C) oxaloacetate.
D) malate.
E) 3-phosphoglycerate.

Answer 14

C) oxaloacetate.

Question 15

The synthesis of glycogen, starch, and sucrose all:

A) involve addition of a sugar residue at the reducing end of the growing polymer.
B) take place in liver and muscle of mammals.
C) use a sugar nucleotide as substrate.
D) use glucose 1-phosphate as the only substrate.
E) use glucose-6-phosphate as substrate.

Answer 15

C) use a sugar nucleotide as substrate.

Question 16

The synthesis of starch and sucrose in plants uses _________ as the substrate, rather than _________,
which is used in the synthesis of glycogen in animal cells.

A) ADP-fructose; UDP-glucose
B) ADP-glucose; UDP-glucose
C) fructose 1-phosphate; glucose 1-phosphate
D) glucose 1-phosphate; glucose 6-phosphate
E) UDP-glucose; ADP-glucose

Answer 16

B) ADP-glucose; UDP-glucose

Question 17

The precursors for sucrose biosynthesis are:

A) glucose and fructose
B) UDP-glucose and fructose 6-phosphate
C) UDP-fructose and glucose 6-phosphate
D) UDP-glucose and fructose
E) UDP-glucose and UDP-fructose

Answer 17

B) UDP-glucose and fructose 6-phosphate

Question 18

The major regulator of sucrose biosynthesis in plants is:

A) fructose 2,6-bisphosphate
B) fructose 1,6-bisphosphate
C) sucrose
D) glucose and fructose
E) glucose 6-phosphate

Answer 18

A) fructose 2,6-bisphosphate

Question 19

A precursor in the synthesis of the peptidoglycan of bacterial cell walls is UDP-:

A) galactose.
B) glucose.
C) glucuronic acid.
D) N-acetylglucosamine.
E) penicillin

Answer 19

D) N-acetylglucosamine.

Question 20

Penicillin inhibits the synthesis of peptidoglycan:

A) branches.
B) chains.
C) crosslinks.
D) precursors.
E) all of the above.

Answer 20

C) crosslinks.

Question 21

Which one of the following reactions, cycles, or pathways is not found in plant systems?

A) The Calvin cycle
B) The gluconeogenesis pathway
C) The glyoxalate cycle
D) The rubisco reaction
E) The urea cycle

Answer 21

E) The urea cycle

Question 22

Which one of the following cellular organelles is not unique to plant cells, in carrying out the
indicated pathway or function of carbohydrate metabolism?

A) Amyloplasts (starch synthesis)
B) Chloroplasts (Calvin cycle)
C) Glyoxysomes (glyoxlate cycle)
D) Mitochondria (citric acid cycle)
E) Vacuoles (organic acid storage)

Answer 22

D) Mitochondria (citric acid cycle)

Question 23

Which one of the following sugar phosphates is not part of the pool of readily interconvertible
metabolites used by the plant cell?

A) Dihydroxyacetone phosphate
B) Fructose 2,6-bisphosphate
C) Glucose 1-phosphate
D) 6-phosphogluconate
E) Xylulose 5-phosphate

Answer 23

B) Fructose 2,6-bisphosphate

Question 24

When glycerol is converted to glucose via gluconeogenesis in germinating seeds, the first glycolytic
intermediate formed is:

A) 1,3-bisphosphoglycerate.
B) dihydroxyacetone phosphate.
C) glycerol 1,3-bisphosphate.
D) glycerol 3-phosphate.
E) ribulose 1,5-bisphosphate.

Answer 24

B) dihydroxyacetone phosphate.