Deck 10: Photosynthesis

Question 1

Plastoquinone (PQ),an electron carrier of small molecular weight,is found in the electron transport chain associated with photosystem II.If PQ is not directly anchored to other membrane or cytoplasmic structures,it is probably

A)mobile in the thylakoid membrane.
B)lipid soluble.
C)a molecule that serves as a shuttle between the electron transport chain and ATP synthase.
D)both A and B.

Answer 1

D

Question 2

Chlorophylls absorb light in which colors of the visible range?

A)green and blue
B)blue and red
C)green and red
D)orange and blue

Answer 2

B

Question 3

Which of the following statements about photosynthesis and cellular respiration is TRUE?

A)Photosynthesis is a catabolic process;cellular respiration is an anabolic process.
B)Photosynthesis occurs in plants and some prokaryotes;cellular respiration occurs in animals,but not plants.
C)Organelles are required to carry out photosynthesis and cellular respiration in eukaryotes.
D)Both photosynthesis and cellular respiration require CO₂ as an input.

Answer 3

C

Question 4

The process of photosynthesis probably originated

A)in plants.
B)in prokaryotes.
C)in fungi.
D)three separate times.

Question 5

What is the difference between NAD⁺ and NADP?

A)NAD⁺ functions as an electron transporter,whereas NADP does not.
B)NAD⁺ functions as a free energy source for cells,whereas NADP does not.
C)Both function as electron carriers,but NADP has a phosphate group and NAD⁺ does not.
D)Both transport electrons to the electron transport chain (ETC)found on the inner mitochondrial membrane,but NADP transfers its electrons to the ETC at a higher energy level.

Question 6

What event accompanies energy absorption by chlorophyll (or other pigment molecules of the antenna complex)?

A)ATP is synthesized from the energy absorbed.
B)A carboxylation reaction of the Calvin cycle occurs.
C)Electrons are stripped from NADPH.
D)An electron is excited.

Question 7

As electrons are passed through the system of electron carriers associated with photosystem II,they lose energy.What happens to this energy?

A)It excites electrons of the reaction center of photosystem I.
B)It is lost as heat.
C)It is used to establish and maintain a proton gradient.
D)It is used to phosphorylate NAD⁺ to NADPH,the molecule that accepts electrons from photosystem I.

Question 8

The proteins of the electron transport chain active in the light-dependent reactions

A)are membrane proteins present in the thylakoid.
B)are free proteins present in the thylakoid lumen.
C)are part of the reaction center of photosystem I.
D)have hydrophilic exterior surfaces.

Question 9

Based on what you know about the structure and function of the antenna complex,irradiating a leaf with which of the following light types would result in the release of the greatest quantities of oxygen?

A)red and orange light
B)green and blue light
C)blue and orange light
D)red and blue light

Question 10

Besides proteins,thylakoid membranes must contain a large number of ________ molecules in the reaction centers in order to harvest light energy.

A)phospholipid
B)oligosaccharide
C)pigment
D)electron carrier

Question 11

In autumn,the leaves of deciduous trees change colors.This is because the chlorophyll is degraded,and

A)the carotenoids and other pigments are still present in the leaves.
B)degraded chlorophyll becomes a pigment with different colors.
C)water supply to the leaves has been reduced.
D)the cells of the leaves begin to die.

Question 12

The absorption spectrum of a plant shows what wavelengths of light the plant absorbs.The absorption spectrum depends on

A)the wavelengths of light that hit the plant.
B)wavelengths of light that are transmitted by the plant.
C)wavelengths of light to which the plant's pigments respond.
D)the thickness of the plant's leaves.

Question 13

What is a difference between chlorophyll a and chlorophyll b?

A)Chlorophyll a is a pigment,and chlorophyll b is the enzyme that transfers excited electrons from chlorophyll a to electron carriers of the thylakoid membrane.
B)Chlorophyll a absorbs yellow light,and chlorophyll b absorbs green.
C)Chlorophyll a contains Mg⁺⁺ in a ring structure,whereas chlorophyll b contains iron.
D)Chlorophyll a and b absorb light energy at slightly different wavelengths.

Question 14

If pigments from a particular species of plant are extracted and subjected to paper chromatography,which of the following is the most believable result?

A)Paper chromatography for the plant would isolate a single band of pigment that is characteristic of the particular plant.
B)Paper chromatography would separate the pigments from a particular plant into several bands.
C)The single band of pigment that is isolated is always some shade of green.
D)Paper chromatography isolates only the pigments that reflect green light.

Question 15

Why are there several structurally different pigments in the reaction centers of photosystems?

A)Excited electrons must pass through several pigments before they can be transferred to electron acceptors of the electron transport chain.
B)This setup enables the plant to absorb energy from sunlight from a variety of wavelengths.
C)They enable the plant to absorb more photons from light energy,all of which are at the same wavelength.
D)They enable the reaction center to excite electrons to a higher energy level.

Question 16

Which of the following statements concerning chloroplasts is false?

A)They are unrelated to plastids.
B)They have outer and inner membranes.
C)They have their own DNA.
D)They have an internal membrane system known as the thylakoids.

Question 17

Which of the following is FALSE regarding photosynthesis?

A)It first appeared in ancient prokaryotes.
B)The earliest form of photosynthetic reactions oxidized (used)H₂O and yielded O₂.
C)Development of oxygenic photosynthesis led to atmospheric changes that allowed evolution of cells/organisms able to use aerobic respiration.
D)Some forms of photosynthesis involve oxidizing compounds such as ferrous iron or H₂S.

Question 18

Early investigators thought the oxygen produced by photosynthetic plants came from carbon dioxide.In fact,it comes from

A)water.
B)glucose.
C)H₂S.
D)electrons from NADPH.

Question 19

What capability of flavonoids,found in plants,protects their leaves from damage due to ultraviolet light?

A)their ability to stabilize free radicals
B)their ability to absorb visible light
C)their ability to absorb infrared light
D)their ability to absorb ultraviolet light

Question 20

Energy from sunlight can excite electrons,kicking them out of their orbitals and creating free radicals.Free radicals are highly reactive atoms or molecules that have unpaired electrons.They degrade and destroy other compounds in their vicinity.Carotenoids,one of the pigments present in most chloroplasts,can stabilize these free radicals.This suggests that

A)once chloroplasts are destroyed,the free radicals will destroy the cell.
B)carotenoids probably have a protective function in the cell.
C)other pigments (besides carotenoids and chlorophyll)are essential for the health of a plant cell.
D)carotenoids communicate directly with the immune system of plants.

Question 21

In the carbon fixation step of the Calvin cycle,ribulose-1,5-bisphosphate (a five-carbon compound)is carboxylated to produce

A)citric acid.
B)2 three-carbon compounds.
C)acetyl CoA (two carbons)and oxaloacetate (four carbons).
D)glucose.

Question 22

Data suggest that rubisco (ribulose-1,5-bisphosphate carboxylase)makes up 10% of the total protein found in spinach leaves.Research elucidating the structure of rubisco shows that it has four active sites.Why,with four active sites,might there be such a large concentration of rubisco in plant matter?

A)All heterotrophic organisms depend on plants,either directly or indirectly,for their food supply.
B)Rubisco is a very slow enzyme;what it lacks in speed,it makes up in numbers.
C)Rubisco catalyzes four of the six reactions found in the Calvin cycle.
D)Three of the four active sites bind carbon dioxide;only one binds ribulose-1,5-bisphosphate.

Question 23

The electrons of photosystem II are excited and transferred to electron carriers.From which molecule or structure do the photosystem II replacement electrons come?

A)the electron carrier,plastocyanin
B)photosystem I
C)water
D)oxygen

Question 24

During a discussion of photosynthesis,you are given the following series of facts: 1.Photosystem P700 alone is involved.
2)Water-splitting is not occurring.
3)A proton gradient is created in the Thylakoid lumen.
To which of the following processes do these statements collectively refer?

A)linear electron transport
B)cyclic electron transport
C)the Calvin cycle
D)the Krebs cycle (Citric Acid Cycle)

Question 25

In photosynthesis,what is the role of water (H₂O)?

A)It accepts electrons liberated from the reaction centre of photosystem I.
B)It donates electrons to replace lost electrons in the reaction centre of photosystem II.
C)It provides the necessary H+ ions needed to reduce glyceraldehyde-3-phosphate (G3P).
D)It provides O2,the terminal electron acceptor for the electron transport chain.
E)It allows cyclic photophosphorylation to occur when ATP levels are low in the stroma.

Question 26

The final electron acceptor(s)associated with photosystem I is

A)oxygen.
B)hydrogen ions.
C)NADP.
D)pheophytin.

Question 27

Both C₃ and C₄ plants have the enzymes of the Calvin cycle.How are C₄ plants more efficient than C₃ plants at fixing carbon?

A)In C₄ plants,carbon fixation takes place in mesophyll cells,whereas the Calvin cycle takes place in bundle-sheath cells.
B)Both the carbon fixation reaction and the Calvin cycle take place in mesophyll cells,but the carbon fixation reactions take place in the dark,and the Calvin cycle is light dependent.
C)C₄ plants do not have rubisco and therefore do not undergo photorespiration.
D)C₄ plants fix carbon using the Calvin cycle;C₃ plants use the reverse of glycolysis,a series of reactions that requires more energy in the form of ATP.

Question 28

Melvin Calvin introduced radiolabeled carbon dioxide into plants.Which of the following molecules should he have expected to see radiolabeled first?

A)oxaloacetate
B)succinate
C)glutamate
D)3-phosphoglycerate

Question 29

Most of the enzymes of the Calvin cycle also function in other metabolic pathways.This should not be a surprising finding,because

A)metabolic reactions are catalyzed by enzymes that have multiple functions.
B)there is a close relationship between carbohydrate synthesis and metabolic breakdown.
C)the Calvin cycle is nearly ubiquitous in cells,as are metabolic pathways.
D)the Calvin cycle probably evolved at the same time as did glycolysis.

Question 30

How are the light-dependent and light-independent reactions of photosynthesis related?

A)They cannot occur in the absence of light.
B)The products of light-dependent reactions are used in light-independent reactions.
C)The products of light-independent reactions must be present for light-dependent reactions to take place.
D)They are not related.

Question 31

How does carbon fixation differ between C₃ and C₄ plants?

A)C₄ plants undergo carbon fixation by carboxylation of a four-carbon substrate (oxaloacetate),while in C₃ plants,a three-carbon compound (phosphoglycerate)is carboxylated.
B)Both C₃ and C₄ plants involve carboxylation of ribulose-1,5-bisphosphate by rubisco;but in C₃,the first stable intermediate is 3-phosphoglycerate,and in C₄,it is oxaloacetate.
C)C₃ plants don't undergo photorespiration,but C₄ plants do.
D)Rubisco is the primary enzyme that catalyzes carbon fixation in C₃ plants,and phosphoenolpyruvate carboxylase can catalyze carbon fixation in C₄ plants.

Question 32

In the light dependent reactions of photosynthesis,the plant cell will conduct both linear and cyclic electron transport.This is needed because

A)linear electron transport processes do not absorb enough light to allow for the synthesis of ATP.
B)more NADPH is needed compared to ATP in the subsequent light independent reactions (Calvin cycle).
C)more ATP is needed compared to NADPH in the subsequent light independent reactions (Calvin cycle).
D)electrons are accepted by ferrodoxin during electron transport and without this,ATP synthesis would not occur.

Question 33

Photorespiration is

A)not a problem,because oxygen is not available in the chloroplast where photorespiration takes place.
B)a process involving addition of oxygen to ribulose-1,5-bisphosphate and the formation of ribose-1,5-diphosphate.
C)a process involving the addition of oxygen to ribulose-1,5-bisphosphate and the formation of the products 3-phosphoglycerate and 2-phosphoglycolate.
D)a process involving the carboxylation of ribulose-1,5-bisphosphate.

Question 34

CAM plants function using crassulacean acid metabolism.Like C₄ plants,CAM plants provide a preparatory step for the Calvin cycle.CAM plants are found in hot,dry environments;to prevent dessication,they keep their stomata closed during the day.They take in carbon dioxide at night while stomata are open.To increase the concentration of carbon dioxide available to the enzyme rubisco and minimize the degree of photorespiration,the CAM plants carboxylate

A)phosphoenolpyruvate.
B)oxaloacetate.
C)organic acids.
D)ribose.

Question 35

Purple photosynthetic bacteria do not contain chloroplasts.They have an antenna system that includes two light-harvesting protein complexes,both of which are integral membrane proteins.The bacteriochlorophyll a molecules contain Mg²⁺ and absorb light at 800 nm.Which of the following statements comparing photosynthesis in purple bacteria and plant chloroplasts is true?

A)Because purple bacteria do not have chloroplasts,there is no electron transport associated with photosynthesis.
B)Bacteriochlorophyll a is a molecule containing Mg²⁺,whereas chlorophyll a from chloroplasts contains Fe²⁺.
C)Bacteriochlorophyll a absorbs light most efficiently in the ultraviolet range,at a significantly shorter wavelength than that for chlorophyll a of chloroplasts.
D)Plant chlorophyll a absorbs in the visible light range,whereas purple photosynthetic bacteriochlorophyll a absorbs light at a longer wavelength.

Question 36

The light-independent reactions of plants function to make organic molecules using carbon dioxide as a carbon source.What is the electron source that helps reduce carbon dioxide to sugars and other organic molecules?

A)NADH
B)NADPH
C)ATP
D)electrons from oxygen

Question 37

Sagebrush is a C4 plant,while wheat is a C3 plant.Based on the type of photosynthesis that would occur in these plants in an arid (dry)southern region of the United States,which of the following is true?

A)Sagebrush is expected to outcompete wheat in the cooler spring and early summer seasons,whereas wheat outcompetes sagebrush in the hotter mid-to-late summer.
B)Wheat is expected to outcompete sagebrush in the cooler spring and early summer seasons,whereas sagebrush outcompetes wheat in the hotter mid-to-late summer.
C)Sagebrush produces 4 molecules of G3P per 'turn' of the Calvin cycle,while wheat produces only 3 molecules of G3P per "turn" of the Calvin cycle.
D)Sagebrush carries out the initial fixation of CO₂ into an organic acid only at night.
E)Wheat carries out the initial fixation of CO₂ into an organic acid only at night.

Question 38

Stomata,openings in the leaf,are important to photosynthesis for

A)entry of carbon dioxide that is used in the Calvin cycle.
B)entry of oxygen that is used in the Calvin cycle.
C)removal of water and carbon dioxide,the end-products of photo-oxidation.
D)removal of nitrogen-containing waste products.

Question 39

Which of the following procedures would identify the enzyme that catalyzes the carboxylation of ribulose-1,5-bisphosphate?

A)irradiating a leaf extract with red light
B)introducing radiolabeled carbon dioxide into a plant extract and determining which molecules become radiolabeled
C)purifying a variety of proteins from plant extracts and testing each protein individually to see if it can carboxylate ribulose-1,5-bisphosphate
D)differential sedimentation of a protein extract