Deck 6: Photosynthesis and the Chloroplast

Question 1

Chloroplasts were discovered as the site of photosynthesis in an ingenious experiment.What was it?

A)Oxygen could be seen as it was produced in chloroplasts.
B)Chloroplasts were seen to swell in the presence of sunlight.
C)Spirogyra in the dark shrank and their chloroplast disappeared.
D)When Spirogyra was illuminated,actively moving bacteria gathered outside the cell near its large ribbon-like chloroplast to use the oxygen produced there for aerobic respiration.
E)None of these are correct.

Answer 1

D

Question 2

Why are organisms that presently use hydrogen sulfide as an electron source limited in their distribution and importance?

A)It is more efficient.
B)They are smaller.
C)Hydrogen sulfide is abundant and widespread.
D)Hydrogen sulfide is neither abundant nor widespread.
E)In the current environment,hydrogen sulfide combines with silicon dioxide inactivating it.

Answer 2

D

Question 3

The chloroplast internal membrane is organized into flattened membranous sacs called _________;they,in turn,are arranged in orderly stacks called _______ that contain energy-transducing machinery

A)thylakoids,grana
B)grana,thylakoids
C)thylakoids,stroma thylakoids
D)thylakoids,grana thylakoids
E)grana thylakoids,thylakoids

Answer 3

A

Question 4

A direct advantage of using water as an electron source for photosynthesis was that _________.

A)organisms could live in fewer habitats than they could previously
B)organisms could get larger
C)organisms were able to live in a much more diverse array of habitats
D)organisms could be smaller
E)organisms could be rehydrated more readily

Question 5

The outer membrane of the chloroplast contains _____ like the outer membrane of ______.

A)carbohydrates,mitochondria
B)carbohydrates,peroxisomes
C)several different porins,mitochondria
D)mitochondria,porins
E)several different porins,nucleus

Question 6

It is much _____ to pull electrons from water than hydrogen sulfide,since the sulfur atom in hydrogen sulfide has much ______ affinity for its electrons than the oxygen atom in water.

A)harder,lower
B)harder,higher
C)easier,lower
D)easier,higher
E)easier,more moderate

Question 7

The earliest photosynthetic organisms on Earth probably used what substance as an electron source for photosynthesis?

A)water
B)hydrogen sulfide
C)hydrogen sulfite
D)carbon dioxide
E)carbohydrates

Question 8

Why was the number of heterotrophs on primitive Earth likely to have initially been severely restricted?

A)The spontaneous production of organic molecules occurs very slowly.
B)The spontaneous production of organic molecules occurs very quickly.
C)The early heterotrophs could not reproduce.
D)The early heterotrophs reproduced too quickly.
E)Organic molecules spontaneously broke down keeping their amounts low.

Question 9

Organisms that use the energy stored in inorganic molecules,like ammonia,hydrogen sulfide or nitrites,to convert carbon dioxide to organic molecules like carbohydrates and proteins are called _____.

A)chemoautotrophs
B)chemoheterotrophs
C)photoautotrophs
D)photoheterotrophs
E)didliotrophs

Question 10

Organisms that depend on an external source of organic compounds are called _________.

A)autotrophs
B)heterotrophs
C)chemotrophs
D)phototrophs
E)externotrophs

Question 11

The non-pigmented precursors of chloroplasts are called __________.

A)prechloros
B)preplastids
C)proplastids
D)prochloroplasts
E)prechloroplasts

Question 12

Organisms that use the radiant energy of the sun to convert carbon dioxide to organic molecules like carbohydrates and proteins are called _____.

A)chemoautotrophs
B)chemoheterotrophs
C)photoautotrophs
D)photoheterotrophs
E)didliotrophs

Question 13

Where are the enzymes that synthesize carbohydrates located?

A)grana
B)thylakoids
C)the lumen
D)stroma
E)chloroplast envelope

Question 14

What metabolic process below do all eukaryotic green algae and higher plants have in common?

A)glycolysis
B)photosynthesis
C)transcription
D)translation
E)All of these are correct.

Question 15

Photoautotrophs include _________.

A)plants
B)eukaryotic algae
C)various flagellated protists
D)members of several groups of prokaryotes
E)All of these are correct.

Question 16

Which of the following is not a usual component found in the stroma?

A)tRNAs
B)prokaryote-like ribosomes
C)circular DNA
D)linear DNA
E)many different polypeptides

Question 17

The raw materials that the earliest forms of life on Earth used for nutrients were produced ______.

A)artificially
B)biotically
C)abiotically
D)supernaturally
E)quickly

Question 18

Thylakoid membranes have ___________.

A)high protein content
B)relatively plentiful phospholipids
C)a low percentage of galactose-containing glycolipids
D)low protein content
E)high amounts of phospholipids

Question 19

How did the evolution of photosynthesis set the stage for the evolution of aerobic respiration?

A)Photosynthesis produces a waste product (carbon dioxide)that led to the evolution of aerobic respiration.
B)Photosynthesis produces a waste product (oxygen)that led to the evolution of aerobic respiration.
C)Photosynthesis uses carbon monoxide in the atmosphere.
D)Photosynthesis produces a waste product (sulfur)that led to the evolution of aerobic respiration.
E)Photosynthesis inhibits glycolysis.

Question 20

Flattened membranous structures that connect the thylakoids of different grana are known as ______.

A)grana thylakoids
B)stroma thylakoids
C)grana
D)lumen
E)stroma

Question 21

Photosynthetic light absorption occurs in large pigment-protein complexes called __________.

A)pigmentoses
B)pigmentosystems
C)antennoids
D)photoids
E)photosystems

Question 22

You are studying mutant algal cells that lack carotenoids.You raise them in an aerobic environment.They do not survive.Why?

A)They cannot absorb any light.
B)They reflect all colors of light.
C)They dissipate aerobic environments.
D)They transfer excess energy to O₂ making ultrareactive singlet oxygen that can destroy biological molecules and cause cell death.
E)The lack of carotenoids causes the chloroplast membranes to disintegrate.

Question 23

What do sulfur bacteria use as a source of electrons in photosynthesis?

A)hydrogen sulfide
B)water
C)hydrogen sulfite
D)carbon dioxide
E)glucose

Question 24

To what type of molecule does pheophytin pass its photoexcited electron?

A)theophyllin
B)plastoquinone
C)another pheophytin
D)xanthophylls
E)succinate dehydrogenase

Question 25

The shared properties of the two photosystems (I and II)with respect to protein composition and overall architecture suggest that __________.

A)both absorb exactly the same wavelength of light
B)all photosynthetic reaction centers have evolved from a common ancestral structure that has been conserved for a long time (more than 3 billion years)
C)all photosynthetic reaction centers have their own unique ancestor
D)all photosynthetic reaction centers have evolved separately within the last 100,000 years
E)all photosynthetic reaction centers evolved from unrelated structures

Question 26

What is the plant cell's primary source of reducing power?

A)CO₂
B)ADP
C)ATP
D)NAD
E)NADPH

Question 27

What metal atom is part of the chlorophyll porphyrin ring?

A)magnesium
B)manganese
C)platinum
D)iron
E)aluminum

Question 28

Carotenoids ________.

A)absorb primarily blue light
B)absorb primarily green light
C)reflect orange and red light
D)reflect yellow light
E)All of these are correct.

Question 29

What group of organisms is thought to responsible for converting about 500 trillion kg of CO₂ to carbohydrate each year?

A)plant life
B)phytoplankton
C)fungi
D)bacteria
E)moss

Question 30

Which type of chlorophyll is found in brown algae,diatoms and certain protozoa?

A)Chlorophyll a
B)Chlorophyll b
C)Chlorophyll c
D)Bacteriochlorophyll
E)carotenoids

Question 31

Which type of chlorophyll is found in red algae?

A)Chlorophyll a
B)Chlorophyll b
C)Chlorophyll c
D)Chlorophyll d
E)carotenoids

Question 32

What group of organisms is responsible for most of the photosynthesis that occurs on Earth?

A)green plants
B)phytoplankton
C)fungi
D)bacteria
E)moss

Question 33

What part of the chlorophyll molecule absorbs light?

A)the phytol chain
B)the porphyrin ring
C)the iron containing heme group
D)the polypeptide backbone
E)the perforin ring

Question 34

The LHCII complex binds pigments and holds them in close contact with one another.What is the advantage of the close contact between the pigments?

A)The close contact facilitates rapid energy transfer toward the photosystem interior.
B)The close contact facilitates rapid energy transfer toward the photosystem exterior.
C)The close contact helps with fluorescence.
D)The close contact helps prevent denaturation.
E)The close contact facilitates renaturation.

Question 35

You are growing algae in culture and expose them to CO₂ that contains radiolabeled oxygen.Where does the radiolabeled oxygen end up after photosynthesis?

A)water
B)oxygen
C)carbon dioxide
D)carbohydrates
E)carbon monoxide

Question 36

The light-driven splitting of a water molecule is known as _______.

A)hydrolysis
B)photonization
C)photolysis
D)condensation
E)dehydration

Question 37

As energy passes through a photosynthetic unit,it is transferred to a pigment molecule that absorbs at a(n)______ wavelength,so energy is _____ and the nature of future transfers becomes restricted.

A)equal or longer,lost
B)equal or longer,gained
C)equal or shorter,gained
D)equal or shorter,lost
E)equal,the same

Question 38

The excited PSII reaction-center pigment (P680*)transfers a single photoexcited electron to a closely associated,chlorophyll-like molecule called _________.

A)theophyllin
B)carotene
C)pheophytin
D)xanthophylls
E)succinate dehydrogenase

Question 39

What is the minimum number of photons needed to make one molecule of O₂ during photosynthesis?

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

Question 40

About how many chlorophyll molecules are found in a single photosynthetic unit and how many of those chlorophyll molecules actually transfer electrons to an electron acceptor?

A)300,200
B)300,1
C)300,300
D)2400,300
E)2,1

Question 41

How does paraquat destroy human tissue?

A)It competes with ferredoxin for electrons from the PSI reaction center.
B)It interferes with PSI function.
C)Electrons attached to paraquat are used to reduce nitrogen,generating highly reactive nitrogen radicals.
D)It leads to the production of substances that damage and kill the tissue.
E)It generates oxygen radicals using electrons diverted from complex I of the respiratory chain.

Question 42

What is the mechanism of action by which the herbicide paraquat kills plants?

A)It competes with ferredoxin for electrons from the PSI reaction center.
B)It interferes with PSI function.
C)Electrons attached to paraquat are used to reduce oxygen,generating highly reactive oxygen radicals.
D)It leads to the production of substances that damage the chloroplasts and kill the plant.
E)All of these are correct.

Question 43

______is a small,water-soluble,iron-sulfur protein that transfers electrons to NADP⁺ to form NADPH.

A)ferritin
B)sulfotriene
C)sulfate
D)ferredoxin
E)sulferritin

Question 44

Why are plants unlikely to produce many carbohydrates at night?

A)Selected Calvin cycle enzymes are inactive in the dark because they denature at night.
B)Selected Calvin cycle enzymes are immobilized at night.
C)Chloroplasts shrink at night.
D)Selected Calvin cycle enzymes are inactive in the dark because thioredoxin is oxidized and cannot reduce their disulfide linkages.
E)Selected Calvin cycle enzymes are inactive in the dark because thioredoxin is reduced and can break their disulfide linkages.

Question 45

The reduction of ________ is accomplished with electrons passed through ferredoxin;this substance then reduces certain _______ in selected Calvin cycle enzymes.

A)thioredoxin,disulfide bridges
B)thioredoxin,sulfhydryl groups
C)sulfhydryl groups,thioredoxin
D)disulfide bridges,thioredoxin
E)thioredoxin,hydrogen bonds

Question 46

Algal cultures in sealed containers were exposed to radiolabeled [¹⁴C]O₂ for a brief incubation period.Soluble molecules were extracted from the algae and subjected to 2D-paper chromatography.How many carbons are found in the most predominant spot on the chromatogram?

A)2
B)1
C)3
D)4
E)6

Question 47

Calvin originally thought that the acceptor molecule for carbon dioxide during carbon fixation contained how many carbons?

A)2
B)1
C)3
D)4
E)6

Question 48

A cluster of what kind of ions is responsible for passing electrons one-at-a-time to the nearby P680+ in the reaction center?

A)a cluster of iron ions
B)a cluster of 4 manganese ions and one calcium ion
C)a cluster of magnesium ions
D)a cluster of copper ions
E)a cluster of manganese ions

Question 49

Starch stored as granules in the chloroplasts serves what purpose?

A)It causes plant cells to swell.
B)It provides plants with sugars at night when light-dependent reactions are not possible.
C)It provides plants with cellulose during the day.
D)It supplies plants with ribulose bisphosphate.
E)It causes plant cells to shrink.

Question 50

Why is the conversion of CO₂ to a 6-carbon sugar so energetically expensive?

A)CO₂ is the most highly reduced and least energetic form in which carbon can occur.
B)CO₂ is very unstable.
C)CO₂ is the most highly oxidized and least energetic form in which carbon can occur.
D)CO₂ is the most highly oxidized and most energetic form in which carbon can occur.
E)CO₂ is highly unstable and only moderately energetic which makes the process more expensive energetically.

Question 51

What is the mechanism by which the herbicides diuron,atrazine and terbutryn are able to kill plants?

A)They bind to the manganese ions of chlorophyll.
B)They block electron transport through PSII.
C)They act as competitive inhibitors of reduced plastiquinone binding to chlorophyll a.
D)They act as noncompetitive inhibitors of reduced plastiquinone binding to the D1 protein of PSII.
E)They bind to hemoglobin.

Question 52

What waste product of photolysis is released to the environment?

A)carbon dioxide
B)water
C)oxygen
D)ammonia
E)precipitated manganese

Question 53

Which molecule carries electrons to the luminal side of the positively charged PSI reaction center where they are transferred to pigment P700⁺,the positively charged reaction-center pigment of PSI?

A)cytochrome b₆f
B)plastocyanin
C)phytochrome
D)cytochrome c
E)oxygen

Question 54

A mechanism that is known to regulate basic cell processes,like protein folding,transcription,translation and chloroplast metabolism,by controlling the activity of proteins is known as ________.

A)transubstantiation
B)internal combustion
C)redox control
D)oxidation inhibition
E)reduction counter-regulation

Question 55

The initial product of carbon fixation contains ____ carbons,but it breaks down into two compounds containing _____ carbons.

A)8,4
B)6,3
C)6,6
D)10,5
E)12,6

Question 56

Which molecule conveys protons from the chloroplast stroma into the thylakoid lumen?

A)cytochrome b₆f
B)plastocyanin
C)phytochrome
D)cytochrome c
E)oxygen

Question 57

The production of ATP in chloroplasts and mitochondria differs in which of the following ways?

A)The protons move into the stroma in chloroplasts and out of the mitochondria.
B)In mitochondria,the force is expressed primarily as an electrochemical potential;in chloroplasts,it is largely,if not exclusively,due to a pH gradient.
C)In mitochondria,the force is expressed primarily as a pH gradient;in chloroplasts,it is largely,if not exclusively,due to an electrochemical potential.
D)The protons move into the intermembrane space in chloroplasts and into the thylakoid lumen in mitochondria.
E)The protons move into the matrix in mitochondria and into the cytoplasm in chloroplasts.

Question 58

Why does an electrochemical potential build up in mitochondria,but not in chloroplasts?

A)Proton movement into the thylakoid lumen is compensated for (neutralized)by the movement of other ions.
B)Proton movement into the intercristal space is compensated for (neutralized)by the movement of other ions.
C)Proton movement into the cristae lumen is compensated for (neutralized)by the movement of other ions.
D)The protons in chloroplasts are immediately joined to electrons.
E)The protons in mitochondria are immediately joined to electrons.

Question 59

In chloroplasts,a proton gradient is established with a higher concentration of protons found in the ______ and a lower concentration in the ______.

A)thylakoid lumen,intermembrane space
B)intermembrane space,thylakoid lumen
C)thylakoid lumen,stroma
D)stroma,thylakoid lumen
E)intermembrane space,matrix

Question 60

Mercaptoethanol is a reagent that breaks disulfide linkages.If you were to treat Calvin cycle enzymes with this reagent,what effect might it conceivably have on them?

A)It might competitively inhibit them.
B)It might noncompetitively inhibit them.
C)It might split them in two pieces.
D)It might activate them.
E)It might deactivate them.

Question 61

Why is the process whereby O₂ is added to RuBP called photorespiration?

A)because O₂ is released and CO₂ is taken up
B)because CO₂ is released and O₂ is taken up
C)because breathing is necessary
D)because RuBP is released
E)because it occurs in crop plants

Question 62

What substance is attached to RuBP by Rubisco to make 2-phosphoglycolate?

A)ATP
B)O₂
C)CO₂
D)NADPH
E)glycolate

Question 63

What determines the direction of the Rubisco-catalyzed reaction?

A)the concentration of O₂ alone
B)the concentration of CO₂ alone
C)the CO₂/O₂ ratio available to the enzyme
D)Rubisco itself
E)cofactors for Rubisco

Question 64

Why might Rubisco have evolved with an inability to distinguish between CO₂ and O₂?

A)Rubisco may have evolved at a time when atmospheric O₂ levels were virtually nonexistent.
B)Rubisco may have evolved at a time when atmospheric CO₂ levels were virtually nonexistent.
C)Rubisco evolved when atmospheric O₂ levels were high.
D)Rubisco possesses four subunits.
E)Rubisco denatures due to photorespiration.

Question 65

What enzyme is the first enzyme in the C₄ Hatch-Slack pathway that carries CO₂ into the bundle sheath cells?

A)Rubisco
B)phosphenolpyruvate carboxylase
C)pyruvate carboxylase
D)phosphoenolpyruvate decarboxylase
E)ATP synthase

Question 66

Why does Rubisco show relatively little preference for CO₂ as a substrate over O₂?

A)Both CO₂ and O₂ bind directly to Rubisco's active site.
B)CO₂ and O₂ bind to RuBP,which occupies the active site;their ability to attack RuBP is roughly equal.
C)Rubisco binds to a regulatory site.
D)CO₂ and O₂ bind to a regulatory site instead of the active site.
E)Both O₂ and CO₂ are repelled RuBP.

Question 67

What enzyme is responsible for fixing CO₂ out of the atmosphere in C₄ plants?

A)PEP decarboxylase
B)ATP synthase
C)PEP carboxylase
D)Rubisco
E)ribulose bisphosphate carboxylase

Question 68

What substance is made in the mesophyll cells of CAM plants during the nighttime fixation of CO₂ and then stored in the cell's central vacuole?

A)malate
B)oxygen
C)RuBP
D)PEP
E)water

Question 69

2-phosphoglycolate is converted into glycolate by an enzyme in the ________.

A)peroxisome
B)glyoxysome
C)stroma
D)thylakoid disk
E)thylakoid membrane

Question 70

The rate of photosynthetic CO₂ fixation _____ and the rate of the release of CO₂ by photorespiration _______ when _____ plants are grown in a closed container.

A)decreases,increases,C₃
B)increases,decreases,C₃
C)decreases,increases,C₄
D)decreases,decreases,C₃
E)increases,increases,C₃

Question 71

Why is CO₂ split off of the C₄ carriers once they get into the bundle sheath cells?

A)so that the CO₂ can be used by Rubisco to initiate the Calvin cycle
B)so that the CO₂ can be used by PEP carboxylase to initiate the Calvin cycle
C)so that the CO₂ can be used by Rubisco to initiate the Hatch-Slack pathway
D)so that the CO₂ can be used by PEP carboxylase to initiate the Hatch-Slack pathway
E)so that the O₂ can be used by Rubisco to initiate the Calvin cycle

Question 72

What anatomical specialization is typical of C₄ plants?

A)Mesophyll cells are scattered throughout the interior of the leaf.
B)Bundle sheath cells are scattered throughout the interior of the leaf.
C)C₄ plants have two concentric cylinders of cells around their vascular tissue.
D)The leaves are coated with extra waxy material.
E)Rubisco floats free in the air spaces in the leaves of C₄ plants.

Question 73

Across which structure is malate transported for the purpose of storing it in the cell's central vacuole?

A)the plasma membrane
B)the nuclear membrane
C)the tonoplast membrane
D)the lysosomal membrane
E)the ER membrane

Question 74

If Calvin cycle enzymes are treated with a reagent that stabilizes their disulfide linkages,what effect might the treatment have on the enzymes?

A)It might competitively inhibit them.
B)It might noncompetitively inhibit them.
C)It might split them in two pieces.
D)It might activate them.
E)It might deactivate them.

Question 75

What is the difference between the way C₃ and C₄ plants fix CO₂ from the atmosphere?

A)C₃ plants fix CO₂ and conduct the light-dependent reactions in the same cells;C₄ plants conduct these activities in different cells.
B)C₄ plants fix CO₂ and conduct the light-dependent reactions in the same cells;C₃ plants conduct these activities in different cells.
C)C₃ plants fix CO₂ and conduct the light-dependent reactions at the same time of day;C₄ plants conduct these activities at different times of the day.
D)C₄ plants fix CO₂ and conduct the light-dependent reactions at the same time of day;C₃ plants conduct these activities at different times of the day.
E)C₃ plants fix CO₂ and conduct the light-independent reactions in the same cells;C₄ plants conduct these activities in different cells.

Question 76

What is the reason that C₃ plants must open their stomata even when the climate is hot and dry?

A)To take in CO
B)To take in CO₂
C)To take in water
D)To let CO₂ out of the leaf
E)To take in O₂

Question 77

Through what structure in mesophyll cells are C₄ products transported to the thick-walled bundle sheath cells?

A)lysosomes
B)plasmodesmata
C)plasma membrane
D)cilia
E)mitochondria

Question 78

How do C₄ plants manage to cause CO₂ fixation to be favored over photorespiration?

A)They can generate high [CO₂]/[O₂] ratios in the local Rubisco environment.
B)They can generate low [CO₂]/[O₂] ratios in the local Rubisco environment.
C)They destroy the cell wall.
D)They convert CO₂ to O₂.
E)They can generate high [CO₂]/[O₂] ratios in the local PEP carboxylase environment.

Question 79

To what organelle is glycolate passed after it is produced in the chloroplast?

A)the peroxisome
B)the glyoxysome
C)the lysosome
D)the Golgi apparatus
E)the rough endoplasmic reticulum

Question 80

How do C₄ and CAM plants overcome the negative effects of photorespiration?

A)They destroy O₂.
B)They chemically alter O₂ before it gets to the enzyme.
C)They employ mechanisms that increase the CO₂/O₂ ratio to which Rubisco molecules are exposed.
D)They chemically alter CO₂.
E)They destroy CO₂.