Deck 21: Photosynthesis

Question 1

Balance the following reaction:
____ NADPH + ____ H⁺ + ____ ATP + ____ CO₂ + 12 H₂ O → C₆H₁₂O₆ + 12 NADP⁺ + 18 ADP + 18 P_i

A) 6; 6; 18; 6
B) 12; 12; 18; 3
C) 6; 6; 12; 6
D) 12; 12; 18; 6
E) 6; 6; 12; 3

Answer 1

D

Question 2

When light energy is absorbed by chlorophyll an electron is promoted to a higher orbital and then transferred to a suitable acceptor resulting in light energy conversion to chemical energy in a(n):

A) isomerase reaction.
B) mutase reaction.
C) ligase reaction.
D) oxidation-reduction reaction.
E) none of the above.

Answer 2

D

Question 3

The light reactions in photosynthetic plants:

A) reduce water to oxygen with the production of NADPH
B) use NADP⁺ to oxidize water to oxygen, thus forming NADPH
C) produce ATP and NADPH during cyclic photophosphorylation.
D) involve the splitting of two water molecules to produce molecular oxygen.
E) uses photons of visible light to effect the reduction of water to oxygen

Answer 3

D

Question 4

The reaction of photosynthesis whereby light energy is transduced into chemical energy uses ____ as a source of carbon, and produces ____.

A) CO₂; hexose
B) hexose; CO₂
C) acetyl CoA; hexose
D) CO₂; acetyl CoA
E) none of the above

Question 5

The essence of photosynthesis is the photochemical event which is:

A) conversion of H₂O to O₂.
B) reduction of NADP⁺.
C) phosphorylation of ADP.
D) light energy transduction to chemical energy.
E) fixation of CO₂.

Question 6

Chloroplasts differ from mitochondria in that:

A) chloroplasts can not generate ATP.
B) only mitochondria have a double membrane.
C) in chloroplasts, the proton gradient is generated between the thylakoid lumen and the stroma.
D) only the mitochondrion has DNA, RNA and ribosomes.
E) chloroplasts do not utilize a Q-cycle.

Question 7

All of the following are involved in the production of biochemical energy from light EXCEPT:

A) electron transfer.
B) Q-cycle.
C) transmembrane pH gradient.
D) ribulose-1,5-bisphosphate.
E) chlorophyll.

Question 8

Carotenoids have primary roles in photosynthesis as:

A) accessory light-harvesting and photooxidation.
B) accessory light-harvesting and photoprotection from reactive oxygen species.
C) resonance transfer pigments and photooxidation.
D) resonance transfer and photodiffusion protection.
E) none are true.

Question 9

How many photons of light must be absorbed by PSII for the oxidation of 2 water molecules to form one oxygen molecule?

A) 2
B) 4
C) 6
D) 8
E) 16

Question 10

All are contained by chloroplasts EXCEPT:

A) thylakoid membrane.
B) ribosomes.
C) DNA and RNA.
D) stroma.
E) all are true.

Question 11

Many chlorophyll molecules absorb light and direct the energy to the reactive centers. The transfer of this absorbed energy is called:

A) fluorescence transfer.
B) redox transfer.
C) resonance energy transfer.
D) photochemical emission.
E) energy transduction.

Question 12

Chlorophyll is located in the ____ of the chloroplast.

A) thylakoid membranes associated with proteins
B) thylakoid spaces associated with rubisco
C) stroma
D) inner membrane space
E) outer membrane

Question 13

Which of the following statements about the light reactions of photosynthesis is true?

A) There are two distinct photosystems, linked together by a mechanism similar to electron transport.
B) The source for electrons is located in the stroma of the thylakoid.
C) The Mn complex is the primary electron acceptor and is located on photosystem I.
D) The ultimate electron donor is molecular oxygen.
E) Plastoquinone is a fixed electron transporter in the system located in the inner membrane.

Question 14

Photosynthesis occurs in photosynthetic ____ localized in large organelles known as ____.

A) membranes; chloroplasts
B) proteins; ribosomes
C) matrix; chloroplasts
D) membranes; photoplasts
E) none are true

Question 15

Properties of photosystem II (PSII) include all EXCEPT:

A) light-driven O₂ evolution.
B) similar photosystem in photosynthetic bacteria.
C) use quinines as terminal electron acceptors.
D) found in cyanobacteria, green algae and higher plants.
E) all are true.

Question 16

Characteristics of chlorophyll include all EXCEPT:

A) iron-containing porphyrin.
B) planar conjugated porphyrin ring.
C) long-chain phytol tail.
D) delocalized π electrons in the aromatic ring.
E) photoexcitable electrons.

Question 17

Chloroplasts consist of a folded inner membrane called the ____, which is organized into paired folds called ____.

A) thylakoid membrane; stroma
B) lamellae; thylakoid membrane
C) thylakoid membrane; lamellae
D) stroma; thylakoid membrane
E) lamellae; stroma

Question 18

The photosynthetic unit includes all EXCEPT:

A) antenna chlorophylls.
B) the reactive center.
C) oxidation of chlorophyll to a cationic free radical, Chl ^.+ .
D) the cationic free radical is the Mg²⁺ ion.
E) all are true.

Question 19

All are properties of both the P700 and P680 reaction centers EXCEPT:

A) contain chlorophyll dimers.
B) are electron donors.
C) are activated by visible light.
D) are involved in light-driven O₂ evolution.
E) all are properties.

Question 20

If A and B represent electron-transfer molecules adjacent to chlorophyll (Chl) in the membrane, fill in the reaction sequence:

A) Chl; Chl; A−; Chl⁺; B−
B) Chl*; Chl*; A−; Chl; B⁺
C) Chl*; Chl*; A⁺; Chl−; B⁺
D) Chl−; Chl−; A⁺; Chl; B−
E) Chl−; Chl−; A−; Chl⁺; B−

Question 21

Spinach chloroplasts are illuminated in the absence of ADP and P_i, then the light is turned off and ADP and P_i are added. ATP is then synthesized for a short time in the dark. Which of the following best explains this?
I)
ATP is generated from the proton gradient accumulated in the light reactions.
II)
ATP synthesis stops after the proton gradient dissipates.
III)
ATP can be generated in the dark reactions if it becomes necessary for the plant to survive.

A) I, III
B) I only
C) II only
D) I, II
E) II, III

Question 22

Cyclic photophosphorylation takes place when:

A) there is not enough light to activate the PSII complex.
B) NADPH is high, therefore energy is used to drive the citrate cycle.
C) ferredoxin is used to reduce the Mn-cluster.
D) the proton gradient is not high enough to go all the way through the system.
E) NADPH/NADP⁺ ratio is high, energy is used in generating ATP.

Question 23

All are true for cyclic photophosphorylation EXCEPT:

A) oxygen is evolved.
B) utilizes cyt b₆ of cyt f/cyt b₆ complex.
C) does not utilize ferredoxin.
D) PS I is involved.
E) all are true.

Question 24

____ and ____ are produced in the light reactions of photosynthesis which are used to convert ____ to ____.

A) ATP; NADPH; carbon dioxide; sugar
B) oxygen; ATP; NADPH; carbon dioxide
C) ATP; NADP⁺; carbon dioxide; sugar
D) oxygen; NADPH; ATP; sugar
E) NADPH; ATP; sugar; carbon dioxide

Question 25

Characteristics of the chloroplast's ATP synthase include all EXCEPT:

A) contains CF₁CF₀ complex.
B) heteromultimer of subunits.
C) imbedded in the thylakoid membrane.
D) has 14 c-subunits in its F₀ rotor.
E) all are true.

Question 26

The proton-motive force is composed of a ____ and a ____, and in photophosphorylation the ____ is greater.

A) pH gradient; ATP/H⁺ ratio; ATP/ H⁺ ratio
B) ATP/ H⁺ ratio; ion equilibrium; ion equilibrium
C) membrane potential; pH gradient; membrane potential
D) membrane potential; pH gradient; pH gradient
E) ATP/ H⁺ ratio; membrane potential; membrane potential

Question 27

Light-dependent electron flow with the production of ATP can occur without the formation of NADPH. This process is called ____, which involves only one of the photosystems, ____.

A) noncyclic photophosphorylation; P700
B) cyclic photophosphorylation; P700
C) noncyclic photophosphorylation; photosystem II
D) noncyclic photophosphorylation; P680
E) cyclic photophosphorylation; P680

Question 28

Which statement regarding light is NOT true?

A) the energy of a photon of light is calculated by E=hν
B) the energy of 700nm light is greater than that of 400nm light
C) photosynthesis allows two electrons to flow for each pair of photons absorbed per center
D) the quantum yield of photosynthesis can be described as CO₂ fixed per photon absorbed, or O₂ evolved per photon absorbed
E) none are true

Question 29

Many of the enzymes of the Calvin cycle are also involved in ____; however, the glyceraldehyde-3-phosphate dehydrogenase of the Calvin cycle is specific for ____.

A) glycolysis; NADPH
B) citric acid cycle; NADH
C) glycolysis; FADH₂
D) citric acid cycle, NADPH
E) none of the above

Question 30

Photophosphorylation is the term for:

A) activation of enzymes with light
B) ATP synthesis driven by light energy
C) dephosphorylation of ATP, resulting in a photon of light being released
D) production of hexose from CO₂
E) none are true

Question 31

Photosynthetic phosphorylation and oxidative phosphorylation are similar processes. All of the following are common to BOTH processes EXCEPT:

A) both have fixed and mobile electron carriers.
B) both contain cytochromes in their electron carrier chains.
C) both produce NADPH to be used in the reductive pentose phosphate pathway (Calvin cycle).
D) both represent a major route of ATP synthesis.
E) both have quinones as electron carriers.

Question 32

Via PSII and PSI, electrons ultimately flow from ____ to ____.

A) NAPDH; O₂
B) NADP⁺; water
C) water; NADP⁺
D) O₂; NADPH
E) None are true

Question 33

The quantum yield of photosynthesis can be defined as the amount of ____ formed per equivalent of ____.

A) photons; light input
B) product; light input
C) ATP; coenzyme Q
D) carbohydrate; ATP
E) none are true

Question 34

The product(s) of the R. viridis photosynthetic reaction center is (are):

A) mobile reduced quinone.
B) NADPH.
C) O₂.
D) reduced ferredoxin.
E) protons.

Question 35

All are correct statements about rubisco EXCEPT:

A) ribulose-1,5-bisphosphate and carbon dioxide are both substrates.
B) the catalytic site has both carboxylase and oxygenase activity.
C) it is found in the chloroplast stroma.
D) it releases two molecules of glyceraldehyde-3-phosphate as products.
E) it may be the most abundant enzyme in plants.

Question 36

Which of the following is the product of cyclic photophosphorylation?

A) NADPH
B) Molecular oxygen
C) ATP
D) ADP and P_i
E) Electron gradient

Question 37

All are correct about reactions of the Calvin cycle EXCEPT:

A) ATP is hydrolyzed to ADP.
B) NADP⁺ is reduced to NADPH.
C) an intermediate is fructose-1,6-bisphosphate.
D) some of the enzymes are shared by glycolysis.
E) involves a ribulose-5-phosphate kinase.

Question 38

What type of enzyme catalyzes the reaction?
Erythrose-4-P + dihydroxyacetone phosphate (DHAP) ⇔ sedoheptulose-1,7-bisphosphate

A) isomerase
B) aldolase
C) transaldolase
D) transketolase
E) mutase

Question 39

Which of the following is an outcome of ferredoxin passing electrons to cytochrome f / cytochrome b₆ complex?

A) proton gradient formation
B) ATP synthesis
C) NADPH production
D) oxygen evolution
E) both A and B occur

Question 40

The appropriate sequence of events for activation of rubisco is:
A)carboxylation of E
B)ribulose-1,5-bisphosphate released from E
C)rubisco activase
D)Mg²⁺ binding
E)light flash

A) C, E, D, A, B
B) C, D, A, B, E
C) B, C, D, A, E
D) E, B, C, D, A
E) E, C, B, A, D

Question 41

What type of enzyme catalyzes the reaction?
Sedoheptulose-7-P + glyceraldehyde-3-P ⇔ xylulose-5-P + ribose-5-P

A) isomerase
B) lyase
C) transaldolase
D) transketolase
E) aldolase

Question 42

All of the following are characteristics of a C-4 plant EXCEPT:

A) PEP carboxylase.
B) transport of carbon dioxide and reducing power from the mesophyll cells to the bundle sheath cells.
C) pyruvate-P_i dikinase.
D) the expenditure of two high-energy phosphate bonds for each transport of carbon dioxide.
E) carbon dioxide uptake in the daytime and fixation at night.

Question 43

To avoid futile cycling of carbohydrates:

A) CO₂ fixation by Calvin cycle proceeds in the dark.
B) citric acid cycle, glycolysis and oxidative phosphorylation are inhibited when light is present.
C) the enzymes of the Calvin cycle are inhibited by light reactions.
D) plants do not have glycolytic and citric acid cycle enzymes.
E) none of the above.

Question 44

All of the following are characteristics of CAM plants EXCEPT:

A) the stroma are open during the night and closed during the day.
B) they try to avoid loss of water by evaporation.
C) there is an accumulation of CO₂ fixation into the organic acids OAA and malate.
D) during the night, dicarboxylic acid are stored within the vacuoles.
E) CO₂ is fixed by rubisco during the night.

Question 45

During photosynthesis-linked carbohydrate synthesis in plants, the products of photosynthesis are required for the actual fixation of carbon. Which of the following correctly explains the use of the products of photosynthesis?

A) NADPH is required for the actual reduction of CO₂ by the RUBISCO enzyme.
B) ATP is used primarily during the regeneration of ribulose-1,5-bisphosphate
C) Oxygen is used during the oxidation of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate
D) Protons from the formation of the proton gradient are required to activate the RUBISCO enzyme
E) Both A and B are correct

Question 46

Which of the following is true regarding CO₂ fixation in plants?

A) CAM plants work by storing carbon dioxide at night in the form of oxaloacetate
B) The RUBISCO enzyme has a higher affinity for oxygen than for CO₂, making it very difficult to effectively fix CO₂
C) At high temperatures, C4 plants are more efficient than C3 plants because they are able to fix CO₂ with minimal photorespiration
D) The RUBISCO enzyme contains a Mg²⁺ that acts as a Lewis base, binding to CO₂ and making it more susceptible to nucleophilic attack
E) None of the above are true

Question 47

The general flow of electrons in plant photosynthesis is from PSII to PSI. Which of the following correctly explains the events that occur during this process?

A) The oxidation of water occurs at PSI with the electrons being passed to ferredoxin to reduce NADP⁺.
B) Protons are pumped into the lumen at PSII during water reduction and also by the cytochrome bf complex allowing for ATP synthesis to occur.
C) A cyclic flow of electrons is created between ferredoxin, cytochrome bf complex, and PSI that allows for the production of NADPH without the generation of ATP.
D) For each electron removed from a water molecule, 2 photons are required to transfer it to ferredoxin.
E) None of the above

Question 48

Although the ratio of carboxylase to oxygenase activity of rubisco is about ____ to one, the oxygenase activity diminishes plant productivity because of the loss of ____.

A) one; rubisco
B) two; ribulose-5-phosphate
C) 3-4; ribulose-1,5-bisphosphate
D) 6-8; rubisco
E) 8-10; ribulose-5-phosphate

Question 49

The reaction, Ribulose-5-phosphate + ATP → Ribulose-1,5-bisphosphate + ADP, is catalyzed by:

A) phosphopentose isomerase.
B) phosphoribulose kinase.
C) ribulose bisphosphate carboxylase.
D) phosphopentose epimerase.
E) transketolase.

Question 50

Which of the following set of pathways is similar between plants and animals?
I)
Electron transport and the dark reactions of photosynthesis
II)
Electron transport and the light reactions of photosynthesis
III)
The Hatch-Slack pathway (C-4) and pyruvate carboxylase

A) I only
B) II only
C) III only
D) I, III
E) II, III

Question 51

What type of enzyme catalyzes the reaction?
Sedoheptulose-1,7-bisphosphate + H₂O ⇔ sedoheptulose-7-phosphate + P_i

A) hydrolase
B) isomerase
C) aldolase
D) mutase
E) lyase

Question 52

All of the following are accomplished in the dark reactions of photosynthesis EXCEPT:

A) carbon dioxide is fixed to ribulose-1,5-bisphosphate.
B) two molecules of 3-phosphoglycerate are produced.
C) glyceraldehyde-3-phosphate is used to synthesize glucose.
D) glyceraldehyde-3-phosphate is used to re-synthesize ribulose-1,5-bisphosphate.
E) ATP is produced.

Question 53

The light-induced changes in chloroplasts which regulate key Calvin cycle enzymes include all EXCEPT:

A) activation of rubisco activase.
B) Mg²⁺ efflux from the thylakoid lumen.
C) changes in stromal pH.
D) generation of reducing power.
E) all are true.

Question 54

The essential enzyme in C-4 plants used to conserve CO₂ and avoid photophosphorylation is:

A) rubisco.
B) PEP carboxylase.
C) glyceraldehyde-3-phosphate dehydrogenase.
D) aldolase.
E) ribulose-5-phosphate kinase.

Question 55

Discuss the structure of a plant membrane protein supercomplex consisting of the PSI reaction center and its lightharvesting antenna LHC1 (light-harvesting complex 1).​

Question 56

Discuss the general formulation of the overall reaction of photosynthesis as stated by van Niel.​

Question 57

How is photorespiration avoided in C-4 plants?

A) decrease the concentration of phosphoglycolate.
B) carry carbon dioxide towards an oxygen rich area of the plant.
C) increase the concentration of ribulose-1,5-bisphosphate.
D) transport of carbon dioxide from the mesophyll cells to the bundle sheath cells.
E) none of the above.

Question 58

Discuss the photosystem II supramolecular complex. ​

Question 59

CO₂ fixation is one of the most critical reactions on earth. Which of the following are elements of the reaction catalyzed by the RUBISCO enzyme?

A) Mg²⁺ acts as a Lewis acid, binding to CO₂ and making it more susceptible to nucleophilic attack
B) The 6-carbon enzyme-bound intermediate that forms is split into 2 molecules of 3-phosphoglycerate
C) Biotin is attached to a Lys residue in the active site and serves a critical role in the activation of CO₂
D) ATP is required for the activation of CO2 prior to its reaction with ribulose-1,5-bisphosphate
E) Both a and b occur

Question 60

A new photosystem from a plant with yellow-colored leaves was discovered to have a potential difference of 2.73 volts between the ground and excited states. What wavelength of light is required to excite an electron in this photosystem?

A) 228 nm
B) 455 nm
C) 683 nm
D) 910 nm
E) none of the above

Question 61

What purpose do the Calvin cycle enzymes serve?​

Question 62

Compare the two modes of photophosphorylation.​