Chapter 7: How Cells Capture Light Energy via Photosynthesis
In the Calvin cycle, for every SIX carbon dioxide molecules that are incorporated into a carbohydrate such as glucose, ___________ molecules of ATP are hydrolyzed and __________- molecules of NADPH are oxidized.
18; 12
According to the Z scheme, what is the number of photoactivation events that occur during photosynthesis?
2
The Calvin cycle can be very energy-expensive. How many molecules of ATP and NADPH respectively are required to incorporate one carbon dioxide molecule into the six-carbon sugar being formed?
3 ATP, 2 NADPH
If 14CO2 (radioactive CO2) is added to plants, you might expect the 14C tagged carbon atom to be first found in ______.
3-phosphoglycerate
The human eye can detect light wavelengths between __________ and ____________ nm, which represent that range of the visible spectrum.
380; 740
The production of one molecule of glucose through photosynthesis requires ________ molecules of CO2 and ________ molecules of H2O as reactants.
6; 12
What is a photon?
A discrete particle of light
What environmental condition favors photorespiration?
A hot, dry environment
Which of the following are components of both PSI and PSII?
A light harvesting complex A reaction center
Which of the following best describes the structure of a phytol tail of a chlorophyll a or b?
A long hydrophobic hydrocarbon chain
In photosynthesis, carbon dioxide is reduced and H2O is oxidized. What type of chemical reaction is this?
A redox reaction
A major purpose of the electrochemical gradient generated in the light reactions of photosynthesis is to synthesize _______________.
ATP
Plant cells can produce additional amounts of ______________ to fuel the Calvin cycle in a process known as cyclic photophosphorylation.
ATP
Plants can use cyclic photophosphorylation to increase production of:
ATP
Which of the following are products of the light reactions of photosynthesis that are used as reactants in the Calvin cycle?
ATP NADPH
The Calvin cycle uses more __________ than __________
ATP; NADPH
The electron transport chain directly associated with PSII is used to generate ______, while the electron transport chain directly associated with PSI is used to generate ______.
ATP; NADPH
The light reactions of photosynthesis produce three chemical products:
ATP; NADPH; O2
The Calvin cycle uses energy from ________________, and high-energy ________________ supplied by NADPH.
ATP; electrons
How does the structure of chlorophyll enable its photosynthetic function?
An electron can be delocalized across the porphyrin ring, allowing it to absorb energy.
Which of the following are chloroplast membranes?
An inner membrane An outer membrane The thylakoid membrane
Which of the following summarizes the events of the first phase of the Calvin cycle?
Atmospheric carbon dioxide is fixed into a five carbon sugar.
Why are C3 plants so-named?
Because 3PG is a three-carbon molecule
Why is light considered a form of electromagnetic radiation?
Because it consists of both electric and magnetic energy
Why do hot and dry conditions favor photorespiration?
Because plants close their stomata, inhibiting CO2 uptake and increasing O2
Why is it significant that energy from excited electrons in photosynthesis is "captured"?
Because the energy is not released but instead used productively
Why is it significant that in photosynthesis, photoexcited electrons are passed from one molecule to another?
Because the energy of the electron is "captured" rather than lost to the environment
Why does CO2 enter CAM plants at nighttime?
Because the stomata of CAM plants are only open at night
Why might plants contain a variety of pigments?
Because this feature enables plants to absorb light at many different wavelengths
Within a chloroplast, where is the stroma located?
Between the thylakoid membrane and the inner membrane
What type of organisms carry out cellular respiration?
Both heterotrophs and photoautotrophs
How might a plant increase its efficiency of light absorption?
By diversifying the pigments it has, such that it is able to absorb many wavelengths of light
Ninety percent of the plants on Earth are:
C3 plants
In some plants, carbon fixation yields a four-carbon molecule instead of 3GP as the first product. Such plants are known as _______________ plants.
C4
Sugarcane, crabgrass, and corn are examples of ______ plants.
C4
CAM plants are a type of ______ plant that separate carbon fixation and the Calvin cycle in ______.
C4; time
What represents the balanced products of photosynthesis if we account for the production of glucose (C6H12O6)?
C6H12O6 + 6O2 + 6H2O
Pineapple and cacti are examples of ______ plants.
CAM
____________ plants avoid water loss by closing their stomata during the day and opening them at night.
CAM
How do CAM plants avoid water loss?
CAM plants close their stomata during the day and open them at night.
How do CAM plants differ from C4 plants?
CAM plants fix CO2 by forming a C4 molecule at night when water loss through stomata is minimized.
______ plants only uptake CO2 at night because they close their ______ during the day.
CAM; stomata
Cellular respiration regenerates the ______ that is used during photosynthesis.
CO2
What molecule is reduced during the process of photosynthesis?
CO2
What molecule is reduced in the Calvin cycle?
CO2
What two molecules can be attached to RuBP by the enzyme rubisco?
CO2 O2
What is the general equation for photosynthesis?
CO2 + 2H2O + light energy → CH2O + O2 + H2O
Photosynthesis is a redox reaction where ______ is reduced and ______ is oxidized.
CO2; H2O
In the first phase of the ______, atmospheric carbon dioxide is fixed into a five carbon sugar.
Calvin cycle
Plants take CO2 from the atmosphere via the ______ in order to synthesize carbohydrates.
Calvin cycle
The stroma of the chloroplast is the site where the ______ takes place.
Calvin cycle
What molecule is released during photorespiration?
Carbon dioxide
What is the origin of the carbons in a carbohydrate generated by photosynthesis?
Carbon dioxide in the atmosphere
What chemical reaction is catalyzed by the enzyme rubisco?
Carbon fixation
In a covalent bond between carbon and oxygen, where are the shared electrons located?
Closer to the oxygen atom
What is the purpose of the light reactions of photosynthesis?
Conversion of light energy to chemical energy
Which of the following plants are C4 plants?
Crabgrass Corn Sugarcane
Which of the following organisms are photoautotrophs?
Cyanobacteria Algae Green plants
Which statement best describes linear electron flow?
Electrons move from photosystem II to photosystem I and ultimately reduce NADP+ to NADPH.
What three events can happen after an electron absorbs energy and becomes excited?
Energy may be released as heat. Energy may be released as light. The excited electron may be transferred to another molecule.
True or false: Autotrophs include fungi, animals, and most species of bacteria.
False -- Fungi, animals, and most species of bacteria are heterotrophs.
True or false: Plants are the only living organisms that can conduct photosynthesis.
False -- In addition to plants, algae and some species of bacteria are capable of photosynthesis.
What is the main product of the Calvin cycle?
Glyceraldehyde-3-phosphate
Why is the rate of photosynthesis slow in the green region of the visible light spectrum?
Green light is not absorbed by chlorophyll.
The energy that is released as electrons pass from one electron carrier to the next is used to pump ____________________ ions into the thylakoid lumen.
H+
What is carbon fixation?
Incorporation of carbon into an organic molecule that is not a gas
What is the function of chlorophyll during photosynthesis?
It absorbs light energy.
Which of the following best describes the function of the phytol tail found in chlorophyll a and b?
It anchors the pigment to the thylakoid membrane.
What happens to a pair of electrons after it reaches QB?
It enters an electron transport chain in the thylakoid membrane
Which of the following happens to the molecule formed by the addition of carbon dioxide to ribulose bisphosphate?
It is immediately split into two more stable three carbon molecules.
What three things may happen to light when it strikes an object?
It may change direction. It may pass through the object. It may be absorbed.
How does photosynthesis benefit organisms that are not plants?
It produces oxygen that can be used for aerobic respiration. It produces organic molecules that other organisms use as food.
What is the role of the reaction center in a photosystem?
It transfers a high-energy electron to another molecule.
What energy conversion occurs during photosynthesis?
Light energy is converted to electrochemical energy, which is converted to chemical energy
How does an electron present in the pigment of the light-harvesting complexes become excited?
Light excites an electron in a pigment found in the light-harvesting complexes of the photosystems.
What are the two stages of photosynthesis?
Light reactions Calvin cycle
How is NADPH formed in PSI?
NADP+ reductase adds two electrons and a H+ to NADP+
A key role of PSI is to produce high-energy electrons that are used to make
NADPH
During photosynthesis, _________ serves as an electron carrier that can accept two high-energy electrons.
NADPH
What is the source of electrons used to reduce the C-O bond of 3-phosphoglycerate during the Calvin cycle?
NADPH
What molecule is used as an electron carrier during photosynthesis?
NADPH
Which of the following are major chemical products of the light reactions of photosynthesis?
NADPH ATP oxygen
Which of the following are major chemical products of the light reactions of photosynthesis?
NADPH oxygen ATP
Which of the following are products of the light reactions that are used by the Calvin cycle?
NADPH and ATP
During the Calvin cycle, high-energy electrons are provided by ______, and the source of energy for the reactions is ______
NADPH; ATP
The products of the light reactions of photosynthesis are
NADPH; ATP; oxygen
What is the product of the oxidation of water during photosynthesis?
O2
Which of the following are products of the light reactions?
O2 ATP NADPH
Through the process of photosynthesis, photoautotrophs produce:
O2 organic molecules
The process of photorespiration consumes ______ and produces ______.
O2; CO2
Cyclic electron flow is characteristic of what photosystem in plants?
Only photosystem I
Which of the following occur during hot and dry conditions?
Oxygen builds up in leaves. Stomata close and reduce the intake of CO2 Rubisco's oxidation activity is favored.
Which of the following molecules is found in the reaction center of photosystem II?
P680
In some C4 plants, PEP carboxylase and rubisco function in different cells to minimize the effects of photorespiration. Where are these two enzymes located?
PEP carboxylase is in mesophyll cells, and rubisco is in bundle-sheath cells.
What technique did Calvin and his colleagues use to separate the radiolabeled molecules synthesized by algae in their experiment?
Paper chromatography
What chemical reaction is catalyzed by the enzyme PEP carboxylase?
Phosphoenolpyruvate + CO2 → oxaloacetate
Which of the following reasons may explain why photorespiration continues to occur despite its negative consequences for plants?
Photorespiration protects plants from free radical damage.
Which of the following can oxidize water, resulting in the release of 02?
Photosystem II
Which of the following plants are CAM plants?
Pineapple Cactus
How might you summarize what happens during photosynthesis?
Plants capture energy from sunlight and use it to synthesize organic molecules.
Which of the following would be an appropriate radioactive tracer for studying the flow of carbon through the Calvin cycle?
Radioactive CO2
The G3P produced at the end of the second phase of the Calvin cycle is directly used for which of the following?
Regenerate ribulose bisphosphate Make glucose or other carbohydrates
What are the three phases of the Calvin cycle?
Regeneration of ribulose bisphosphate Carbon fixation Reduction and carbohydrate production
In the last phase of the Calvin cycle, what molecule is regenerated so that the next cycle can occur?
Ribulose bisphosphate
In Calvin's isotope labeling experiment, some molecules appeared very quickly, but others appeared only after long incubations. Which two molecules appeared only after long incubations?
Ribulose bisphosphate Glyceraldehyde-3-phosphate
In linear electron flow, how much of each product is synthesized?
Roughly equal amounts of ATP and NADPH
What two chemical reactions are catalyzed by rubisco?
RuBP + CO2 → 2 3PG RuBP + O2 → 3PG + phosphoglycolate
What enzyme is responsible for carbon fixation?
Rubisco
What is the most abundant protein found in chloroplasts?
Rubisco
What happens during photorespiration?
Rubisco attaches O2 to RuBP, and CO2 is produced.
Which of the following statements about radiation is TRUE?
Shorter-wavelength radiation carries more energy per unit of time than longer-wavelength radiation.
What is photophosphorylation?
Synthesis of ATP powered by light energy
Which of the following parts of photosynthesis occurs during the night in CAM plants?
Synthesis of a C4 molecule
Which of the following conditions affect the way the Calvin cycle operates in photosynthetic organisms?
Temperature Water availability Light intensity
What does the sun radiate?
The entire spectrum of electromagnetic radiation
What part of a photosystem contains dozens of pigment molecules that absorb light photons?
The light-harvesting complex
How is a H+ electrochemical gradient established and maintained in photosynthesis?
The movement of electrons from PSII to PSI The formation of NADPH The splitting of water
What part of a chlorophyll molecule anchors it to proteins within the thylakoid membrane?
The phytol tail
Which of the following accepts an electron from P680?
The primary electron acceptor
Which of the following will remove a high energy electron from P680 and transfer it to a more stable molecule?
The reaction center
What is the name of the space enclosed by the thylakoids?
The thylakoid lumen
Which of the following membranes contains pigments in a green plant?
The thylakoid membrane
Which of the following statements are true of carotenoids?
They are abundant in flowers and fruits. They may appear yellow, orange, or red.
In photosystem II, what happens to the low-energy electrons that are removed from water molecules?
They are used to restore P680+ to P680.
What advantages do C4 plants have over C3 plants in warm, dry climates?
They can minimize photorespiration. They can keep their stomata partially closed during the day to conserve water.
Why are carbohydrates critical for plant cells?
They provide a source of energy and form the precursors for most organic macromolecules
Which of following best describes the location of chlorophyll a and b within the chloroplasts of green plants?
Thylakoid membrane
Which of the following is the purpose of phase 3 of the Calvin cycle?
To create a new 5-carbon sugar for the "next" Calvin cycle
What was the purpose of the experiment in which Calvin and his colleagues injected algae with 14C-labeled CO2, incubated the cells for various time periods, and then separated the radiolabeled molecules with paper chromatography?
To determine the order of reactions in the Calvin cycle
Why is water required for the light reactions of photosynthesis?
To replace the electrons lost from P680
True or false: Photosystem II is the only known protein complex that can oxidize water resulting in the release of O2.
True
True or false: Photoautotrophs metabolize organic molecules via cellular respiration to supply their energy needs.
True -- Photoautotrophs use photosynthesis to produce organic molecules. They can also metabolize these organic molecules via cellular respiration to meet the energy needs of their cells.
The model for photosynthesis that incorporates two photoactivation events and shows the series of energy changes during the light reactions of photosynthesis is called the _____________ scheme.
Z
The ______ scheme describes the energy transitions of electrons as they move through the ______ reactions.
Z; light
In C4 plants, the first product of carbon fixation is:
a four-carbon molecule
Chlorophylls a and b are composed of a porphyrin ring containing
a magnesium ion and a phytol tail.
A photon of light has properties of both
a particle and a wave.
A pigment is a molecule that can:
absorb light
The role of the light-harvesting complex is to:
absorb photons of light
When light strikes an object, the light may pass through the object, have its direction changed by the object (reflected), or be _________ by the object.
absorbed
A graph that represents the wavelengths of light absorbed by a given pigment is called a(n):
absorption spectrum
A(n) _______ ___________ is a diagram that depicts the wavelengths of electromagnetic radiation that are absorbed by a pigment.
absorption spectrum
A(n) ____________ spectrum for photosynthesis shows the rate of photosynthesis plotted as a function of light wavelength.
action
What is a visualization of the rate of photosynthesis plotted as a function of light wavelength?
action spectrum
What happens when a photon of light is absorbed by a pigment molecule?
an electron is boosted to a higher level
How does electromagnetic radiation travel?
as waves
A(n) _____________ can synthesize organic molecules from inorganic molecules, while a(n) ____________ must consume food to obtain organic molecules.
autotroph, heterotroph
Organisms that are able to make organic molecules from inorganic sources, such as carbon dioxide and water, are called
autotrophs
Plants are examples of
autotrophs
Plants are examples of:
autotrophs
A key difference between linear electron flow and cyclic electron flow is that in cyclic electron flow, electrons are ultimately transferred:
back to PSI
Which of the following types of organisms can conduct photosynthesis?
bacteria, algae, plants
The wavelength of visible light is:
between 380 and 740 nm
The _______________ describes the regions on the surface of the Earth and in the atmosphere where organisms live.
biosphere
An object that is __________ in color absorbs nearly all of the light energy falling on it.
black
Plants are able to make glucose from inorganic ___________________ and H2O.
carbon dioxide CO2
The pigment molecules that cause autumn leaves to appear yellow and orange are called
cartenoids
Green plants utilize a and b to absorb light energy in photosynthesis.
chlorophyll
Plants appear green because they contain:
chlorophyll
The green color of plants is due primarily to the absorptive properties of the _____________pigment found in the chloroplasts.
chlorophyll
A leaf that appears green has more of the pigment ___________ than a leaf that appears yellow. A leaf may appear more yellow due to the presence of pigments called ________________.
chlorophyll; carotenoid
Similar to a mitochondrion, a(n) _________________ contains an outer and inner membrane, with an intermembrane space between the two. Unlike a mitochondrion, it also contains chlorophyll-containing membranes called ______________ membranes.
chloroplast; thylakoid
After incubating algae with 14C and incubating the cells for a short time, Calvin separated the radiolabeled molecules that were present using a technique called paper
chromatography
Heterotrophs gain energy by:
consuming organic molecules from the environment
The mechanism in plants that produces ATP but not NADPH is referred to as ________________________ electron flow (due to the path of electrons).
cyclic
The mechanism in plants that produces ATP but not NADPH is referred to as ____________ electron flow (due to the path of electrons).
cyclic or circular
When the level of NADP+ is low, _________ electron flow is favored, while when NADP+ levels are high, _________________ electron flow is favored.
cyclic; linear
In CAM plants, the Calvin cycle occurs:
during the day
In photosynthesis, light energy is transformed into ________________ energy and then into energy stored within energy intermediates.
electrochemical
Light is a type of ______ radiation because it consists of energy in the form of electric and magnetic fields.
electromagnetic
When a pigment molecule absorbs a photon of light, a(n) ________________ is boosted to a higher energy level.
electron
Molecules of carbon dioxide cannot be directly linked to form carbohydrates because the carbon atom in CO2 is:
electron poor
An electron traveling from PSII to PSI releases some of its energy at particular steps and is transferred to the next component that has a higher
electronegativity
After a pair of _____________ reach QB, each enters a transport chain in the thylakoid membrane
electrons
In the visible spectrum, light energy may be absorbed by boosting ______________ to higher atomic energy levels, sometimes called energy shells.
electrons
The light reactions of photosynthesis require water to supply two ____________ that are transferred to P680+.
electrons
NADP+ reductase transfers two ______________ and one _______________ to NADP+ to generate NADPH.
electrons; H+ protons
In photosynthesis, glucose is synthesized from CO2. This reaction is:
endergonic
The production of glucose from carbon dioxide and water is an _________________ reaction that releases a large amount of free energy.
endergonic
During resonance energy transfer, what is transferred from one molecule to another?
energy
Every photon contains a specific amount of
energy
Sunlight provides the ______________ that is needed to make glucose from CO2.
energy
After absorbing energy, an electron is said to be in a(n):
excited state
True or false: All photons contain the same amount of energy.
false -- Each photon carries a specific amount of energy that depends on its wavelength.
True or false: Light has properties of both a particle and an elastic spring.
false -- Elasticity does not describe a property of light. Light has properties of a wave and a particle.
True or false: About 90% of the plant species on Earth are CAM plants.
false -- Most plants on Earth (about 90%) are C3 plants.
True or false: In the reduction phase of the Calvin cycle, ATP is the source of electrons used to reduce a C-O bond to a C-H bond.
false -- NADPH is the source of electrons that will ultimately reduce a C-O bond.
True or false: Photorespiration can completely negate the efficiency of photosynthesis.
false -- Photorespiration reduces the efficiency of photosynthesis by 25-50%.
True or false: The term "C3" was derived from the 3-carbon sugar that represents the end product of photosynthesis
false -- The end product of photosynthesis is a 5-carbon sugar. The first stable product of the Calvin cycle is a 3-carbon molecule.
True or false: The term "C3" was derived from the 3-carbon sugar that represents the end product of photosynthesis. True false question.
false -- The end product of photosynthesis is a 5-carbon sugar. The first stable product of the Calvin cycle is a 3-carbon molecule.
True or false: Glucose is the primary output of the Calvin cycle.
false -- The primary output of the Calvin cycle is glyceraldehyde-3-phosphate, which can be used for glucose synthesis in another set of reactions.
In the process of carbon ____________ , carbon dioxide is incorporated into a molecule of ribulose biphosphate forming an unstable 6 carbon intermediate that immediately splits into two 3-carbon molecules.
fixation
The incorporation of carbon from CO2 in the atmosphere into an organic molecule is called carbon
fixation
Carbohydrates are very important to plant cells because they:
form the building block for many organic macromolecules can be used as an energy reserve
The electrochemical gradient generated in the light reactions of photosynthesis is used primarily to:
generate ATP via ATP synthase
During photosynthesis, CO2 is reduced to produce
glucose
Living organisms that are not plants depend on photosynthesis because photosynthesis produces: (1) organic molecules such as ______________ that can be used for nourishment; and (2) the ________________ gas that makes up a large portion of the Earth's atmosphere.
glucose; oxygen
The end product of phase 2 of the Calvin cycle is G3P. This molecule is used to synthesize ____________________ and to regenerate the starting material __________________ bisphosphate.
glucose; ribulose
Thylakoids (or thylakoid membranes) stack on top of each other to form a(n)
granum
Electrons in an excited state can release energy as ______________ or ____________________ or be transferred to another molecule.
heat; light
Most species of bacteria and protists, as well as all species of fungi and animals, are
heterotrophs
Organisms that acquire energy by consuming organic molecules from the environment are called
heterotrophs
In photosystem II, ________________ -energy electrons are transferred from P680* to pheophytin, and ______________ -energy electrons are transferred to P680+ to produce P680.
high; low
The phytol tail of a chlorophyll a or b molecule is a long __________ chain with a(n) _______________ character.
hydrocarbon; hydrophobic
Most photosynthetic organisms use H2O for photosynthesis, although some bacteria use _________________ sulfide instead of water.
hydrogen
What compound is used by some bacteria instead of water for photosynthesis?
hydrogen sulfide
According to the Z-scheme, electrons:
increase and decrease their energy as they move through the light reactions
Autotrophs sustain themselves by producing organic molecules from:
inorganic molecules
PEP carboxylase does not promote photorespiration because:
it cannot bind O2
Although any green part of a plant can perform photosynthesis, the majority of photosynthesis occurs in the _______________ of the plant.
leaves
In a green plant, the majority of photosynthesis takes place in the:
leaves
Longer wavelength radiation contains ___________ energy per unit time than shorter wavelength radiation.
less
In a cool climate, a C3 plant uses ______ a C4 plant to fix CO2.
less energy than
Several dozen pigment molecules anchored to transmembrane proteins make up the _________________-harvesting complex of a photosystem.
light
The thylakoid membrane is the location of the ___________ reactions of photosynthesis.
light
What is the source of energy for photoautotrophs?
light
_____________ excite(s) electrons in pigment molecules in photosystems I and II.
light
Photosynthesis is divided into two stages: the _______________ reactions and the _______________ cycle.
light; Calvin
The light reactions convert ____________ energy into ___________ energy stored in covalent bonds.
light; chemical
PSI and PSII have two main components: a(n) ________________ harvesting complex and a(n) _________________ center.
light; reaction
Roughly equal amounts of NADPH and ATP are generated in
linear electron flow
The combined action of photosystem II and photosystem I is termed
linear electron flow
In photosynthesis, during ______ electron flow, electrons are ultimately accepted by NADP+. During ______ electron flow, electrons are instead transferred back to photosystem I.
linear; cyclic
Cyclic electron flow is favored when the level of NADP+ is ______, or when ATP levels are ______, while linear electron flow is favored when NADPH is ______.
low; low; low
The space inside a thylakoid, which is enclosed by the thylakoid membrane, is known as the thylakoid
lumen
In C4 plants, CO2 is combined with PEP to produce oxaloacetate. The oxaloacetate is then converted to:
malate
Where are chloroplasts found in a leaf?
mesophyll
Within a leaf, the cells that contain chloroplasts are found in the tissue known as .
mesophyll
In the light reactions, roughly equal amounts of ATP and NADPH are made. However, the Calvin cycle requires
more ATP than NADPH
The electron carrier QB is the:
most electronegative carrier in photosystem II
PEP carboxylase can attach CO2 to phosphoenolpyruvate, resulting in the synthesis of a four-carbon molecule called
oxaloacetate
During photosynthesis, water is:
oxidized
In PSII, water is "split" and the electrons are used to replenish excited electrons that are lost from the photosystem. The loss of electrons during the oxidation of water, results in the formation of ___________ gas.
oxygen
Like rubisco, PEP carboxylase can fix CO2. However, PEP carboxylase does not promote photorespiration because it cannot recognize
oxygen
The splitting of water in photosystem II results in the production of ______________ gas.
oxygen
What molecule is produced by photosystem II?
oxygen
Life on Earth is protected from much of the Sun's ultraviolet radiation by the _______________ layer which forms in the upper atmosphe
ozone
After leaving P680, a high-energy electron is transferred to _______, which diffuses away from the reaction center.
pheophytin, then to QA, and finally to QB
Because they use light energy to drive the synthesis of organic molecules, algae and cyanobacteria are considered:
photoautotrophs
Organisms that synthesize organic molecules using light as a source of energy are called:
photoautotrophs
What type of organisms produce most of the Earth's organic molecules?
photoautotrophs
A discrete particle of light is called a(n)
photon
For an electron to absorb light energy, it must absorb a(n) ______________ that contains enough energy to overcome the energy difference between the orbital the electron is in, and the one to which it will be boosted.
photon
The synthesis of ATP using light as the ultimate energy source is called:
photophosphorylation
In hot and dry conditions, the process of ____________________ can reduce the efficiency of photosynthesis by 25-50%.
photorespiration
In hot dry conditions, rubisco can attach O2 to RuBP in a process called ______. which ultimately produces CO2.
photorespiration
The process by which plants capture light energy and use it to synthesize carbohydrates is called
photosynthesis
During photosynthesis, NADPH is synthesized by:
photosystem I
P680 is located within the reaction center of:
photosystem II
During linear electron flow, the movement of electrons occurs from water to
photosystem II, then to photosystem I, and ultimately are transferred to NADP+.
A molecule that can absorb light energy is called a(n):
pigment
The light-harvesting complex is composed of several dozen ___________ molecules that are anchored to transmembrane proteins.
pigment
Excited electrons are moved out of photosystem II by a carrier called ________________. These electrons enter a cytochrome complex, and then finally are transferred to a small protein called _________________ , which carries the electrons to photosystem I.
plastoquinone; plastocyanin
In a chlorophyll molecule, an excited electron can follow a path around several atoms in the ______________ ring, meaning it is delocalized, and thus able to absorb light energy.
porphyrin
The structure of a chlorophyll molecule consists of a(n) __________ ring and a hydrocarbon tail called a(n) _______ tail.
porphyrin; phytol
The reaction center quickly transfers an electron from P680 to the _________________ ________________ acceptor.
primary electron
During the passage of electrons through the electron transport chain between photosystem II and I, energy is released. This energy is used to:
pump H+
In C4 plants, PEP carboxylase synthesizes oxaloacetate, which is converted to malate. The malate is then broken down into:
pyruvate and CO2
Scientists hypothesize that photorespiration occurs in plants because it helps to protect them from damage caused by free __________________ and other toxic molecules.
radicals
Consider the electromagnetic spectrum. Which of the following correctly describes the order of energy magnitude, starting with the lowest?
radio waves - microwaves - visible light - ultraviolet light - X-rays
In the Calvin cycle, CO2 is:
reduced
Leaves appear green because they __________ green light.
reflect
The biosphere refers to:
regions that contain living organisms
Unlike the pigments in the light-harvesting complex, P680* can:
release its high energy electron to become P680+
The energy of an excited electron can be transferred from one pigment molecule to another via _________________ energy transfer.
resonance
CO2 and H2O are produced during cellular _________________ and consumed during the process of _______________.
respiration; photosynthesis
RuBP carboxylase/oxygenase, also known as ______________ , is the most abundant protein in chloroplasts.
rubisco
The electromagnetic ______ encompasses all possible wavelengths of electromagnetic radiation.
spectrum
Wavelengths of electromagnetic radiation ranges from relatively short wavelengths (gamma rays) to much longer wavelengths (radio waves). The entire range of these wavelengths is called the electromagnetic ___________________
spectrum
The glucose that is made by plant cells can be converted to other carbohydrates, including:
starch sucrose
After glucose molecules are synthesized, they can be linked together to form a polymer called __________________ , which is stored, or used to make the disaccharide __________________________ , which can be transported to other parts of the plant.
starch; sucrose
Which of the following terms refers to a structure that allows carbon dioxide and oxygen to enter and leave a leaf?
stoma
The pores in the surface of a leaf that can participate in gas exchange are called
stomata
The fluid-filled region of the chloroplast between the thylakoid membrane and the inner membrane is known as the
stroma
The reactions of the Calvin cycle occur in the:
stroma
The energy required for the synthesis of glucose from carbon dioxide ultimately comes from
sunlight
During the light reactions of photosynthesis, ATP is produced via the protein ATP __________________ that uses an H+electrochemical gradient.
synthase
During the light reactions of photosynthesis, ATP is produced via the protein ATP ___________________ that uses an H+ electrochemical gradient.
synthase
Some C4 plants are able to minimize photorespiration by anatomically separating:
the Calvin cycle and C4 synthesis
Wavelength refers to:
the distance between the peaks in a wave pattern
Following QB, excited electrons pass down an electron transport chain that is arranged according to:
the electronegativity of electron carriers
The splitting of water, the transfer of high energy electrons from PSII to PSI, and the generation of NADPH all contribute to
the generation of a H+ gradient.
In the Fall, aspen leaves change from a green color to a lovely yellow color. Seasonal color changes in a leaf happen because
the quantity of chlorophyll in a leaf declines, unmasking the carotenoids.
During photosynthesis, oxygen is produced by:
the removal of electrons from water in PS2
Calvin and his colleagues grew algae in the presence of radioactively labeled CO2 in order to determine:
the sequence of reactions in the Calvin cycle
The highest rates of photosynthesis in green plants correlate with:
the wavelengths of light that are absorbed most efficiently
Why are leaves green?
they reflect green light
Chlorophylls a and b are found bound to integral membrane proteins in the _____________ membrane of the chloroplast.
thylakoid
The __________ membrane contains pigment molecules, including chlorophyll.
thylakoid
The ___________ membrane of the chloroplast contains two independent, light capturing complexes of proteins and pigments called photosystems I and II.
thylakoid
The light-harvesting complex is found in the________ membrane.
thylakoid
Photosystems I and II are located in:
thylakoid membrane
Where do the light reactions occur?
thylakoid membrane
Where is the light-harvesting complex found?
thylakoid membrane
A granum is a stack of
thylakoids
True or false: Water is oxidized during the light reactions of photosynthesis.
true
NADPH is produced in the stroma of the chloroplast when ______ are transferred to NADP+.
two high-energy electrons and one H+
When an electron absorbs energy, it becomes
unstable
The pigments in the light-harvesting complex transfer energy:
via resonance energy transfer
During photosynthesis in green plants, what molecule is oxidized?
water
In the light reactions, both photosystems absorb and capture light energy in the form of excited electrons; however PSII is able to oxidize _______________, which results in the production of oxygen.
water
The electrons that exit PSII are replenished by electrons from oxidized _________________, which yields oxygen gas that can be used by plant cells or released to the environment.
water
The energy level of electrons moving from photosystem II to NADP+ is represented by the Z scheme. Which of these molecules contains electrons with the lowest energy level?
water
The oxidation of _____________ results in the formation of oxygen gas and the replenishment of electrons lost from PSII.
water
The Calvin cycle is affected by certain environmental conditions, including light intensity, ________________ availability, and ________________.
water; temperature
The distance between the peaks in a wave pattern is the
wavelength
Electromagnetic radiation travels as ___________ caused by the oscillation of the electric and magnetic fields.
waves
What color object reflects nearly all of the visible light energy falling on it?
white
