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