Deck 16: Photosynthesis

Question 1

The regeneration phase of the dark reactions are best considered in terms of regenerating 6 molecules of ribulose-1,5-bisphosphate, a process that requires 6 ATP. Considering the number of photons required for production of ATP in the light reactions, on average, how many photons must be absorbed for each molecule of ribulose-1,5-bisphosphate regenerated?

A)1.5
B)3
C)4.5
D)6
E)9

Answer 1

A

Question 2

Which of the following depicts the general flow of electrons in the two-photosystem light reactions? (Q = plastoquinone, PC = plastocyanin, Fd = ferredoxin

A)PSI $\rarr$ Q $\rarr$ cytochrome b₆f complex $\rarr$ PC $\rarr$ PSII $\rarr$ 0 Fd $\rarr$ NADP⁺
B)PSI $\rarr$ cytochrome b₆f complex $\rarr$ Q $\rarr$ PC $\rarr$ PSII $\rarr$ Fd $\rarr$ NADP⁺
C)PSII $\rarr$ Q $\rarr$ cytochrome b₆f complex $\rarr$ PC $\rarr$ PSI $\rarr$ Fd $\rarr$ NADP⁺
D)PSII $\rarr$ PC $\rarr$ Q $\rarr$ Fd $\rarr$ PSI $\rarr$ cytochrome b₆f complex $\rarr$ NADP⁺
E)PSII $\rarr$ Fd $\rarr$ PC $\rarr$ cytochrome b₆f complex $\rarr$ PSI $\rarr$ Q $\rarr$ NADP⁺

Answer 2

PSII $\rarr$ Q $\rarr$ cytochrome b₆f complex $\rarr$ PC $\rarr$ PSI $\rarr$ Fd $\rarr$ NADP⁺

Question 3

In the mechanism of Rubisco, what role does the Mg²⁺ play?

A)neutralizes negative charges of active site Asp and Glu, enabling ionization of CO₂
B)activates water molecule that hydrates the carboxy- $\beta$ -keto intermediate
C)complexes with the phosphate on C-1 to hold ribulose-1,5-bisphosphate in the active site
D)repels the product, 3-phosphoglycerate, allowing it to leave the active site more rapidly
E)none of the above

Answer 3

activates water molecule that hydrates the carboxy- $\beta$ -keto intermediate

Question 4

Under what conditions does the cyclic electron flow of photosystem I occur?

A)high NADPH, low ATP
B)low NADPH, high ATP
C)low NADPH, low ATP
D)high NADPH, high ATP
E)under conditions when light is not intense enough to excite PSII

Question 5

Which of the following describes the oxidation reactions for the two manganese ions that undergo oxidation in the oxygen-evolving complex?

A)a Mn²⁺ is oxidized to a Mn⁴⁺ and a Mn³⁺ is oxidized to a Mn⁵⁺
B)a Mn²⁺ is oxidized to a Mn⁵⁺ and a Mn³⁺ is oxidized to a Mn⁴⁺
C)a Mn²⁺ is oxidized to a Mn⁵⁺ and a Mn²⁺ is oxidized to a Mn³⁺
D)a Mn²⁺ is oxidized to a Mn⁵⁺ and a Mn⁴⁺ is oxidized to a Mn⁵⁺
E)two Mn²⁺ are oxidized to Mn⁴⁺

Question 6

The energy available from the protonmotive force across the thylakoid membrane is about 20 kJ/mol of protons. How much energy per mole of photons absorbed by the two photosystems does this equal?

A)13 kJ/mol
B)30 kJ/mol
C)40 kJ/mol
D)60 kJ/mol
E)none of the above

Question 7

Which of the following is required for the reaction catalyzed by rubisco in order to drive the reaction to completion?

A)NADH
B)NADPH
C)ATP $\rarr$ ADP + P_i
D)ATP $\rarr$ AMP + PP_i
E)none of the above

Question 8

Which of the following would have an inhibitory effect upon rubisco?

A)Mg²⁺
B)CO₂
C)H⁺
D)reduced thioredoxin
E)none of the above

Question 9

The following reaction would be catalyzed by which of the following enzymes?

A)ribulose-5-phosphate epimerase
B)transaldolase
C)transketolase
D)triose phosphate isomerase
E)pentose phosphate transferase

Question 10

Which of the following photosynthetic pigments would give rise to the yellow or red color of leaves seen during autumn?

A)chlorophyll a
B)chlorophyll b
C) $\beta$ -carotene
D)phycocyanin
E)none of the above

Question 11

Which of the following shows the overall equation for the light reactions?

A)2 H₂O + 1 NADP⁺ $\rarr$ 1 H⁺ + O₂ + 1 NADPH, requires 4 photons
B)2 H₂O + 1 NADP⁺ $\rarr$ 1 H⁺ + O₂ + 1 NADPH, requires 8 photons
C)2 H₂O + 2 NADP⁺ $\rarr$ 2 H⁺ + O₂ + 2 NADPH, requires 4 photons
D)2 H₂O + 2 NADP⁺ $\rarr$ 2 H⁺ + O₂ + 2 NADPH, requires 8 photons
E)2 H₂O + 2 NADP⁺ $\rarr$ 2 H⁺ + O₂ + 2 NADPH, requires 16 photons

Question 12

What range type(s)of electromagnetic radiation are absorbed by photosynthetic pigments to allow the reactions of photosynthesis to occur?

A)UV only
B)visible only
C)infrared only
D)UV and visible
E)visible and infrared

Question 13

For each molecule of CO₂ fixed by the Calvin cycle, how many ATP and NADPH are required?

A)3 ATP, 1 NADPH
B)3 ATP, 2 NADPH
C)6 ATP, 2 NADPH
D)6 ATP, 3 NADPH
E)none of the above

Question 14

For every 12 molecules of 3-phosphoglycerate produced by rubisco, _____ are converted to hexoses while _____ are recycled to ribulose-1,5-bisphosphate.

A)2; 10
B)4; 8
C)6; 6
D)8; 4
E)10; 2

Question 15

What is the minimum number of photons that must be absorbed by PSII to reduce two molecules of water to one molecule of oxygen?

A)1
B)2
C)4
D)8
E)16

Question 16

Which of the following explains why an electron will eventually travel to a chlorophyll molecule in the reaction center as opposed to just "wandering around" all of the antenna molecules?

A)antenna chlorophyll molecules are associated with proteins and have a higher excited state energy level
B)antenna chlorophyll molecules are associated with proteins and have a lower excited state energy level
C)reaction center chlorophyll molecules are associated with proteins and have a higher excited state energy level
D)reaction center chlorophyll molecules are associated with proteins and have a lower excited state energy level
E)none of the above

Question 17

Which of the following best describes photosynthesis in purple photosynthetic bacteria?

A)a reaction center resembling PSI transfers electrons to plastocyanin
B)a reaction center resembling PSII transfers electrons to plastoquinone
C)water is split by the reaction center that resembles PSII
D)NADPH is generated using electrons from a protein resembling ferredoxin
E)the proton gradient is used for both ATP synthesis and NADPH generation

Question 18

Which of the following carbohydrates is the most common molecule exported by photosynthetic cells for use in other parts of the plant?

A)amylose
B)amylopectin
C)glucose
D)sucrose
E)fructose

Question 19

What specific part of the chloroplast is responsible for the light reactions of photosynthesis?

A)thylakoid lumen
B)thylakoid membrane
C)stroma
D)inner membrane of chloroplast
E)outer membrane of chloroplast

Question 20

Which of the following correctly identifies the proton pumping in the two-photosystem light reactions?

A)PSII: 4 protons; cytochrome b₆f complex: 8 protons
B)cytochrome b₆f complex: 8 protons; PSI: 4 protons
C)PSII: 4 protons; ferredoxin-NADP⁺ oxidoreductase: 4 protons
D)PSII: 4 protons; PSI: 4 protons; ferredoxin-NADP⁺ oxidoreductase: 4 protons
E)none of the above

Question 21

Which of the following acts as a corepressor for the transcription of chloroplast genes?

A)3-phosphoglycerate
B)fructose-1,6-bisphosphate
C)CO₂
D)sucrose
E)none of the above

Question 22

In C₄ plants, CO₂ in the mesophyll cell reacts with _________ to form oxaloacetate while in the bundle sheath cell, _________ undergoes decarboxylation to pyruvate.

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

Question 23

When photorespiration occurs and phosphoglycolate must be salvaged, which of the following occurs during the salvage reactions?

A)NADP⁺ is used in the oxidation of glycolate to glyoxylate
B)NADPH is used in the reduction of hydroxypyruvate to glycerate
C)carbon is lost in the form of CO₂
D)ATP is made during the conversion of phosphoglycolate to glycolate
E)none of the above

Question 24

Reaction of ribulose-1,5-bisphosphate with oxygen and then water results in the following intermediate. Show the resulting products from this reaction:

Question 25

If the following ¹⁴C labeled molecules served as substrates for rubisco (the labeled carbons are indicated with *), where would the ¹⁴C labels end up in the immediate product(s)of the reaction? Draw the product(s), clearly showing which atom(s)would be labeled.

Question 26

If light with an average wavelength of 660 nm is used to power the light reactions of photosynthesis, what is the efficiency in terms of energy captured as NADPH and ATP based upon the following information?
2 H₂O + 2 NADP⁺ $\rarr$ 2 H⁺ + O₂ + 2 NADPH E ^$\circ$ ' = -0.50 V
the oxidation of 2 water molecules with production of 2 NADPH requires 8 photons
12 protons are transported to the thylakoid lumen for each oxygen produced