Deck 15: Photosynthesis

Question 1

The production of O₂ from water supplies an electron first for

A) photosystem I.
B) photosystem II.
C) cytochrome bf complex.
D) plastocyanin.

Answer 1

photosystem II.

Question 2

The formation of ATP is a/an reaction in plants.

A) dark
B) light independent
C) light dependent
D) anaerobic
E) carbon fixation

Answer 2

light dependent

Question 3

Which statement is false about bacteriorhodopsin?

A) It occurs in archaebacteria.
B) A molecule of retinal inside bacteriorhodopsin converts from the trans to the cis configuration when light is absorbed.
C) It creates a light-induced proton gradient across a membrane.
D) Its activity is coupled to PSI and PSII.

Answer 3

Its activity is coupled to PSI and PSII.

Question 4

Cyanobacteria have evolved photosynthetic features not found in green sulfur bacteria. These include

A) cytochrome bc.
B) synthesis of NADH.
C) electron acceptor P700.
D) an oxygen-evolving complex.
E) All of the above

Question 5

In plants, light energy channeled to PSII and PSI drives electron transport through a series of electron carriers. At the same time, protons are translocated into the .

A) stroma
B) lumen
C) granum
D) plasma membrane

Question 6

The source of electrons for green sulfur bacteria is , and the source of electrons for cyanobacteria is .

A) NADPH; NAD⁺
B) H₂S; H₂O
C) H₂O; H₂S
D) cytochrome c; cytochrome bf

Question 7

Which statement is false about the photosynthesis in plants?

A) PSII is not directly exposed to the stroma.
B) PSI produces ferredoxin.
C) ATP is synthesized in the lumen.
D) PQH₂ can diffuse within the thylakoid membrane.

Question 8

Photosynthesis by green sulfur bacteria and cyanobacteria are different because green sulfur bacteria .

A) have only cyclic photosynthesis
B) use photosystem I, but not photosystem II
C) use both photosystems I and II
D) use cytochromes

Question 9

The photosynthetic dark reactions .

A) occur only in the dark nocturnal)
B) are the main source of ATP in photosynthesis
C) convert carbon dioxide to carbohydrates
D) produce the reduced coenzyme NADH

Question 10

Within the chloroplast, grana are .

A) stacks of enfolded thylakoid membrane
B) the stroma
C) stromal lamellae
D) the site of carbon fixation reactions

Question 11

The region of the chlorophyll molecule that helps anchor it in the membrane is the

A) Mg²⁺ ion.
B) chlorin ring.
C) phytol side chain.
D) tetrapyrrole ring.
E) All of the above

Question 12

The main difference between photosynthesis and respiratory electron transport is

A) the tetrapyrolle ring of the pigments involved.
B) the coenzymes that carry electrons.
C) the sources of electrons.
D) the formation of ATP.

Question 13

Plant pigments which can absorb light include

A) chlorophyll a.
B) chlorophyll b.
C) carotenoids and phycobilins.
D) All of the above
E) A and B only

Question 14

What is the correct sequence for the following components in photosynthesis as described by the Z scheme?

A) NADPH → P700 → P700^* → cytochrome bf complex → P680 → P680^* → water
B) Water → P700 → P700^* → cytochrome bf complex → P680^* → P680 → NADPH
C) Water → P680 → P680^* → cytochrome bf complex → P700 → P700^* → NADPH
D) Water → P700 → P700^* → cytochrome bf complex → P680 → P680^* → NADPH
E) NADPH → P680 → P680^* → cytochrome bf complex → P700 → P700^* → water

Question 15

In the Z scheme describing electron flow in photosynthesis, the electron donor to P680 is , while the electron donor to P700 is .

A) H₂O; plastocyanin
B) plastocyanin; H₂O
C) O₂; plastocyanin
D) plastocyanin; O₂
E) O₂; H₂O

Question 16

The site of light-dependent reactions in the chloroplast is

A) the stroma.
B) the thylakoids.
C) the outer membrane.
D) the lumen.
E) All of the above

Question 17

Carotenoids, phycobilins, xanthophylls and chlorophyll molecules that are not in the special pair) .

A) can transfer light energy to chlorophylls
B) can absorb light energy
C) may prevent the formation of reactive superoxide anion
D) A, B and C
E) A and B only

Question 18

Two interdependent processes which comprise photosynthesis are 1) the formation of carbohydrates from CO₂ and 2) the formation of .

A) ADP
B) ATP
C) NAD⁺
D) NADPH
E) B and D

Question 19

Electron carriers between activated P680^* and P700 photosystems include

A) plastoquinones.
B) pheophytin.
C) ferredoxin and iron - sulfur clusters.
D) All of the above
E) A and B

Question 20

Which term is not used for a photosystem or a part of a photosystem?

A) PS I
B) PS II
C) special pair
D) light complexes
E) antenna pigments

Question 21

Which is the correct order for the stages of the Calvin cycle?

A) Carboxylation → Reduction → Regeneration
B) Regeneration → Carboxylation → Reduction
C) Carboxylation → Regeneration → Reduction
D) Reduction → Carboxylation → Regeneration

Question 22

Which is not required to activate rubisco?

A) CO₂
B) Mg²⁺
C) light
D) NADP⁺
E) All of the above are required

Question 23

Which is the proper order of substrates in the synthesis of starch?

A) glucose 1-phosphate → glucose 6-phosphate → ADP-glucose → starch
B) glucose 1-phosphate → fructose 6-phosphate → UDP-fructose → starch
C) glucose 3-phosphate → glucose 1-phosphate → ADP-glucose → starch
D) glucose 6-phosphate → glucose 1-phosphate → ADP-glucose → starch

Question 24

How many ATP molecules are required for the fixation of one CO₂ molecule via the Calvin cycle to a triose phosphate?

A) 1
B) 2
C) 3
D) 4

Question 25

Which statement is false about ferredoxin?

A) It is produced by PSII.
B) It is formed in the stroma.
C) It participates in the reduction of NADP⁺.
D) It can serve as an electron donor to cytochrome bf.

Question 26

What is the main advantage for plants that use the C₄ pathway in addition to the Calvin cycle for the fixation of carbon dioxide?

A) Fewer ATP are consumed to produce carbohydrates using the C₄ pathway as opposed to the Calvin cycle.
B) The C₄ pathway allows for fixation of carbon dioxide at night.
C) The C₄ pathway aids in the avoidance of the oxygenation of ribulose 1,5-bisphosphate.
D) The C₄ cycle allows photosynthesis to occur at a wide range of wavelengths of light.

Question 27

Attempts to genetically modify rubisco to help increase food production might include trying to .

A) enhance the carboxylation reaction and suppress the oxygenation reaction
B) suppress the carboxylation reaction and enhance the oxygenation reaction
C) decrease the value of k_cat by site-directed mutagenesis
D) increase rubiscoʹs activity in the dark

Question 28

Photorespiration in plants involves the .

A) fixation of carbon dioxide to a four-carbon acid
B) light-dependent uptake of O₂ catalyzed by rubisco, followed by the release of CO₂
C) reduction of surface-exposed disulfides in the regulation of rubisco
D) exclusive fixation of carbon dioxide at night by plants such as cacti

Question 29

What is the product of the reaction catalyzed by rubisco in the Calvin cycle?

A) dihydroxyacetone phosphate
B) 3-phosphoglycerate
C) ribose 5-phosphate
D) fructose 6-phosphate

Question 30

Which is not a name for the reactions of the Calvin cycle?

A) proton translocation cycle
B) reductive pentose phosphate cycle
C) C₃ pathway
D) dark reactions

Question 31

Which molecule is the CO₂ acceptor in the first step of the Calvin cycle?

A) rubisco
B) ribulose 1,5-bisphosphate
C) 3-phosphoglycerate
D) glyceraldehyde-3-phosphate

Question 32

The reaction catalyzed by which enzyme in the Calvin cycle is unlikely to be a regulatory step?

A) phosphoglycerate kinase
B) triose phosphate isomerase
C) phosphoribokinase
D) rubisco

Question 33

The synthesis of sucrose in plants occurs in the .

A) cytoplasm
B) chloroplast
C) vacuole
D) lumen

Question 34

The Calvin cycle occurs in the of plant chloroplasts and in the of bacteria.

A) lumen; plasma membrane
B) stroma; cytosol
C) granal lamellae; cytosol
D) stroma; plasma membrane
E) lumen; cytosol

Question 35

The initial reactions of the C₄ pathway occur in the .

A) chloroplast stroma
B) mesophyll cells
C) bundle sheath cell cytosol
D) stomata plasma membrane

Question 36

Which is not an intermediate in the biosynthesis of sucrose in plants?

A) ADP-glucose
B) glucose 6-phosphate
C) fructose 6-phosphate
D) fructose 1,6-bisphosphate

Question 37

Which statement is true about starch?

A) It is synthesized during daylight and consumed at night.
B) Its synthesis occurs at a fairly continuous rate both day and night.
C) Its synthesis is inhibited by high concentrations of 3-phosphoglycerate.
D) Starch can be hydrolyzed by amylase to produce triose phosphates.
E) A and D

Question 38

Which is not a substance produced from the carbon dioxide assimilated via the Calvin cycle?

A) cellulose
B) starch
C) sucrose
D) chitin

Question 39

Which enzyme is not part of the Calvin cycle?

A) triose phosphate isomerase
B) rubisco
C) plastocyanin
D) transketolase

Question 40

The initial carbon dioxide acceptor of the C₄ pathway is .

A) phosphoenolpyruvate
B) oxaloacetate
C) ribulose 1,5-bisphosphate
D) PEP carboxylase

Question 41

The only plant pigments responsible for light harvesting are chlorophylls.

Question 42

The nocturnal fixation of carbon dioxide in cacti helps .

A) stimulate photorespiration
B) minimize use of ATP
C) minimize water loss
D) transport CO₂ to the bundle sheath cells

Question 43

In cacti accumulates in the cell vacuoles at night that is released in the day and decarboxylated.

A) phosphoenolpyruvate
B) malate
C) oxaloacetate
D) bicarbonate ion

Question 44

Which statement is false about C₄ plants?

A) They tend to grow at high temperatures and high light intensities.
B) They decrease the ratio of CO₂ to O₂ in cells where Rubisco is active.
C) Corn is an example of a C₄ plant.
D) They avoid wasteful photorespiration by means of secondary pathways for carbon dioxide fixation.

Question 45

The light reactions of photosynthesis form carbohydrates from ATP, NADPH, H⁺ and CO₂.

Question 46

Solar energy is captured in chemical form as ATP and NADPH by the process of photosynthesis.

Question 47

The light-dependent reactions are located in the thylakoid membrane of chloroplasts, while the dark reactions are located within the lumen.

Question 48

Chlorophyll molecules contain hydrophilic regions containing bonds for light-absorbing and hydrophobic regions anchoring them to membranes.

Question 49

Vitamin K is part of the electron chain in photosystem II.

Question 50

The reactions that allow plants such as cacti and orchids to assimilate carbon at night are referred to as .

A) the Calvin cycle
B) nocturnal photorespiration
C) the C₄ pathway
D) Crassulacean acid metabolism

Question 51

The translocation of protons across the thylakoid membrane creates a proton motive force necessary for ATP synthesis.

Question 52

Photosystems I and II are located in the same region of the chloroplast structure, since both contain chlorophyll.

Question 53

Rubisco often makes up to 50% of the soluble protein in plant leaves.

Question 54

All photosynthetic bacteria give off O₂ as an end-product of photosynthesis.

Question 55

The cytochrome bf complex connects the electron flow from photosystem I (PSI) to photosystem II (PSII) according to the Z scheme describing electron flow in photosynthesis.

Question 56

Dark reactions of photosynthesis must occur in the absence of light.

Question 57

Although a variety of pigments absorb light, only the special pair of chlorophyll molecules at photosystems I and II can become activated and thereby provide electrons for transport.

Question 58

Phycoerythrin and β-carotene absorb light in ranges broader than that absorbed by chlorophylls, and this light energy is ultimately used by the plant for photosynthesis.

Question 59

In plants the light-harvesting complex LHC(II) completely surrounds PSII.

Question 60

On a hot summer day which would you expect about the ratio of oxygenation versus carboxylation of ribulose 1,5-bisphosphate in C₃ plants as compared to a cooler day?

A) No change because oxygenation does not occur in C₃ plants.
B) The ratio is not affected by temperature.
C) The ratio rises due to increased rate of oxygenation.
D) The ratio decreases due to decreased rate of oxygenation.

Question 61

Photorespiration is a vital plant pathway that provides energy for cellular metabolism.

Question 62

The structure of Rubisco is nearly identical in all phototrophs. All known forms of Rubisco have the same number of subunits.

Question 63

In Crassulacean Acid Metabolism CAM) acetate accumulated at night supplies CO₂ for carbon assimilation during the day.

Question 64

In terrestrial plants diffusion of carbon dioxide into plant leaves is controlled by the stomata.

Question 65

The compound 2-carboxyarabinitol 1-phosphate is present in plants only at night and is a strong activator of rubisco.

Question 66

Most plants contain a rubisco enzyme that catalyzes only a carboxylation reaction in the fixation of carbon dioxide.

Question 67

The round (R) and wrinkled (r) peas studied by Gregor Mendel differ in the gene for starch branching enzyme.

Question 68

The CAM pathway and the Calvin cycle generally occur simultaneously in plants during the daytime.

Question 69

The C₄ pathway helps increase the concentration of carbon dioxide in the bundle sheath cells. This is important because the cell walls of these cells are impermeable to gases.

Question 70

Both the C₄ and CAM carbon-assimilation pathways use bicarbonate ions to convert phosphoenolpyruvate to oxaloacetate.