Deck 6: Photosynthesis and the Chloroplast

Question 1

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

Answer 1

D

Question 2

Which 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

Answer 2

E

Question 3

The earliest photosynthetic organisms on Earth probably used __________ as an electron source for photosynthesis.

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

Answer 3

B

Question 4

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.

Question 5

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 6

Where are the enzymes that synthesize carbohydrates located?

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

Question 7

Thylakoid membranes have ___________.

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

Question 8

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 9

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.

Question 10

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

Question 11

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 12

Organisms that can survive on carbon dioxide as their principal carbon source are called ______.

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

Question 13

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, the nucleus

Question 14

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 15

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 16

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 17

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 18

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

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

Question 19

It is much _____ to pull electrons from water than hydrogen sulfide, since the sulfur atom in hydrogen sulfide has a 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 20

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

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

Question 21

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 22

Thylakoid membranes are characterized by possessing ___________.

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

Question 23

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

A)plant life as a whole
B)phytoplankton
C)fungi
D)bacteria
E)mosses

Question 24

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 25

As energy passes through a photosynthetic unit, it is transferred to a pigment molecule that absorbs at an______ 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 26

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

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

Question 27

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

A)CO₂
B)ADP
C)ATP
D)NAD
E)NADPH

Question 28

What metal atom is part of the chlorophyll porphyrin ring?

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

Question 29

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 30

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 31

You expose algae to CO₂ that contains radiolabeled oxygen. Where does the radiolabeled oxygen end up after photosynthesis?

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

Question 32

Which type of chlorophyll is only found in green and purple bacteria?

A)chlorophyll a
B)chlorophyll b
C)chlorophyll c
D)bacteriochlorophyll
E)carotenoids

Question 33

The primary role of amyloplasts in a plant cell is __________________________

A)pollination
B)seed dispersal
C)protection from herbivorous animals
D)protection from herbicides
E)energy storage

Question 34

Formation of chromoplasts from chloroplasts is an adaptation designed to assist in:

A)pollination
B)seed dispersal
C)protection from herbivorous animals
D)protection from herbicides
E)energy storage

Question 35

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

Question 36

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 choices

Question 37

One difference between chromoplasts and gerontoplasts is that:

A)the gerontoplast produces more chlorophyll molecules.
B)the chromoplast produces more chlorophyll molecules,
C)the gerontoplast produces more carotenoid molecules.
D)the chromoplast produces more carotenoid molecules.

Question 38

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

A)chlorophyll a
B)chlorophyll b
C)chlorophyll c
D)bacteriochlorophyll
E)carotenoids

Question 39

The non-pigmented precursors of chloroplasts are called __________.

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

Question 40

Which type of chlorophyll is only found in red algae?

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

Question 41

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 42

The PSII reaction center, also known as P680, _____________.

A)absorbs light most strongly at 680 nm
B)reflects light most strongly at 680 nm
C)reflects light most strongly at 700 nm
D)absorbs light most strongly at 700 nm

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

A)Proton movement into the thylakoid lumen is neutralized by the movement of other ions.
B)Proton movement into the intercristal space is neutralized by the movement of other ions.
C)Proton movement into the cristae lumen is 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 45

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 46

What part of PSII appears to suffer most of the damage from high intensity light?

A)the reaction center photopigment
B)the D1 polypeptide of PSII
C)the electrons
D)NADPH
E)both the D1 polypeptide of PSII and NADPH

Question 47

How does high intensity light supposedly damage PSII?

A)If overexcited, PSII becomes highly acidic.
B)If overexcited, PSII becomes highly basic.
C)If overexcited, PSII can damage PSI.
D)If overexcited, PSII can form toxic oxygen species.
E)If overexcited, PSII dissociates.

Question 48

How does the production of ATP in chloroplasts differ from production in mitochondria?

A)The protons move into the stroma of chloroplasts and out of the stroma of mitochondria.
B)It relies on electrochemical potential in mitochondria and on pH gradient in chloroplasts.
C)It relies on pH gradient in mitochondria and electrochemical potential in chloroplasts.
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 49

To what type of molecule does pheophytin pass its photo-excited electron?

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

Question 50

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 5 iron ions
B)a cluster of 4 manganese ions and one calcium ion
C)a cluster of one magnesium ion and 4 calcium ions
D)a cluster of 5 copper ions
E)a cluster of 5 manganese ions

Question 51

High intensity light has a negative effect on photosynthesis; in fact, too much light can diminish photosynthetic output. This phenomenon is known as _______.

A)photousurpation
B)photodiminishment
C)photoinhibition
D)photosynthetic diminishment
E)disinhibition

Question 52

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 53

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 54

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

Question 55

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

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

Question 56

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 57

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 58

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 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

What waste product of photolysis is released to the environment?

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

Question 61

What substance reacts with RuBP by Rubisco to make 2-phosphoglycolate?

A)ATP
B)O₂
C)CO₂
D)NADPH
E)glycolate

Question 62

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 63

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 64

Why are plants unlikely to produce many carbohydrates at night?

A)Selected Calvin cycle enzymes are inactive in the dark because they are hydrogen-bound at night.
B)Calvin cycle enzymes are denatured in the cold temperatures at night.
C)Selected Calvin cycle enzymes are inactive in the dark because thioredoxin is oxidized and cannot reduce their disulfide linkages.
D)Selected Calvin cycle enzymes are inactive in the dark because thioredoxin is reduced and can break their disulfide linkages.

Question 65

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

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

Question 66

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

A)low atmospheric O₂ levels when Rubisco evolved
B)low atmospheric CO₂ levels when Rubisco evolved
C)high atmospheric O₂ levels when Rubisco evolved
D)multiple subunits in the Rubisco enzyme competing for substrate
E)selective advantages for plants that are able to bind both CO₂ and O₂

Question 67

If Calvin cycle enzymes are treated with a reagent that stabilizes their disulfide linkages, what is the likely?

A)It would competitively inhibit them.
B)It would noncompetitively inhibit them.
C)It would split them in two pieces.
D)It would activate them.
E)It would prevent them from catalyzing photosynthetic reactions.

Question 68

When cyclic photophosphorylation is inhibited, which result would be expected?

A)accelerated NADH production
B)impaired development of higher plants
C)increased ATP production
D)improved growth of algae and simple plants

Question 69

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

A)Rubisco's active site can bind to CO₂ and O₂ equally well.
B)CO₂ and O₂ bind to RuBP which has roughly equal affinity for CO₂ and O₂.
C)Ancient atmospheric conditions had high amounts of O₂ which selected for Rubisco to bind to either molecule.
D)CO₂ and O₂ bind to a regulatory site on Rubisco instead of the active site.

Question 70

What determines the direction of the Rubisco-catalyzed reactions?

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

Question 71

Noncyclic photophosphorylation is characterized by:

A)involvement of PSII, not PSI
B)a requirement for CO₂
C)a requirement for oxidized NADP
D)a requirement for sunlight

Question 72

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 73

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 74

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 75

Mercaptoethanol is a reagent that breaks disulfide linkages. If you were to treat Calvin cycle enzymes with this reagent, what is the likely effect?

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

Question 76

When ATP is formed during oxygenic photosynthesis, the process is known as ________________.

A)cyclic photophosphorylation
B)noncyclic photophosphorylation
C)dark reactions
D)proton-motive photophosphorylation

Question 77

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 78

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

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

Question 79

Algal cultures in sealed containers were exposed to radiolabeled [¹⁴C] CO₂ for a brief incubation period of just a few seconds. Soluble molecules were extracted from the algae and subjected to 2D-paper chromatography. How many carbons are found in molecules from the most predominant spot on the chromatogram?

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

Question 80

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

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