Chapter 6

What happens during the light-independent reactions, also called the Calvin Cycle?

Glucose is produced.

What is a photosystem?

a cluster of chlorophyll molecules arranged in a network

Which types of organisms that conduct photosynthesis?

algae, bacteria, & plants

The light-______ reactions are necessary for making ATP to power the light-______ reactions of photosynthesis.

dependent; independent

The thylakoid membrane is impermeable to protons, so the protons pumped into the thylakoid space during the light reactions build up and are only able to re-enter the stroma when they ______.

diffuse through ATP synthase

When a pigment in a photosystem captures photons of light energy, ______.

electrons are boosted to higher energy levels

In the diagram of a photosystem, what is being transferred between the pigment molecules, as indicated by the yellow line?

excitation energy

The electron transport system takes energy from ______ to pump protons across the thylakoid membrane.

excited electrons

Energy captured by a photosystem eventually finds its way to a special chlorophyll molecule that will ______.

pass the captured energy to a membrane-bound acceptor protein

In trees, the leaf is the major site of ______.

photosynthesis

The molecules made during photosynthesis are ______.

transported to other parts of the plant

In the light-dependent reactions of photosynthesis, electrons given up by the reaction center chlorophyll in photosystem II are replaced by those from

a water molecule.

What carries excited electrons from photosystem II to photosystem I?

an electron transport system

In photosynthesis, when an electron is boosted to a higher energy level, ______.

energy has been captured

All of the energy used by almost all living cells on Earth comes from the sun and is harnessed by plants, algae, and some bacteria through the process of

photosynthesis

In plants and algae, a complex of chlorophyll molecules and accessory pigments embedded within a matrix of protein molecules is called a _____________, which occurs in the membranes of thylakoids.

photosystem

The image shows a(n) ______ within the thylakoid membrane of a chloroplast.

photosystem

THe NADPH produced in photosynthesis is made when ______.

photosystem I passes electrons to NADP+ along with H+ to form NADPH

At which photosystem is water split and oxygen produced?

photosystem II

In plants, what photosystem acts first in the light-dependent reactions?

photosystem II

In noncyclic photophosphorylation, what is the path of electrons?

photosystem II, photosystem I, NADPH

In the diagram of a photosystem, what do the green circles represent?

pigment molecules

Chloroplasts are able to absorb light because they contain molecules called ______.

pigments

Molecules that absorb wavelengths of light energy are called ______.

pigments

In bacteria, the proteins involved in the light-dependent reactions are embedded in the

plasma membrane.

What are the two main wavelengths of light that chlorophyll absorbs?

red and blue

True or false: Plant pigments absorb photons from a wider spectrum of wavelengths than the pigment retinal does.

false

In the electromagnetic spectrum, photons with higher energy

have shorter wavelengths.

The molecules containing energy used by the roots, stems, and other parts of the plant are ______.

transported there from the sites of photosynthesis

In the first step of the Calvin cycle, a carbon atom is added to ______ to produce ______.

a five-carbon sugar; two three-carbon sugars

In the C4 pathway, carbon is first fixed to produce

a four-carbon molecule.

What molecule in a photosystem eventually transfers a high-energy electron to a protein that acts as an electron acceptor?

a key chlorophyll molecule

Pigments are defined as molecules that ______.

absorb photons of light

Stomata in the epidermis of the leaf ______.

allow gases to enter and exit the leaf

What part of the light-dependent reactions involves the movement of protons through special channels to make ATP?

chemiosmosis

ATP provided by ______ powers the reactions of the Calvin cycle, and NADPH provided by ______ is a source of electrons and hydrogens for the Calvin cycle.

chemiosmosis; the electron transport chain of photosystem I

A special ______________ molecule is responsible for transferring an excited, high-energy electron to an acceptor protein molecule located in the thylakoid membrane.

chlorophyll

The main photosynthetic pigment in plants is

chlorophyll

The molecule that is embedded in the thylakoid membranes within chloroplasts and that is able to absorb light is called ______.

chlorophyll

The two common forms of chlorophyll found in plants are ______.

chlorophyll a and chlorophyll b

The reaction center is a

chlorophyll a molecule that transfers an electron to an electron acceptor.

In the light-dependent reactions of photosynthesis, water molecules are split by an enzyme and replace electrons lost by Multiple choice question. NADPH in the second electron tran

chlorophyll at photosystem II.

The organelle in the mesophyll cells of a plant where the energy of light is absorbed is the ______.

chloroplast

Underneath the epidermis of the plant leaf are the mesophyll cells, which contain numerous _________________ , the organelles responsible for photosynthesis.

chloroplast

Referring to the diagram, the stoma is one of many such pores in the ______ of the leaf that allow the movement of CO2 and O2 into or out of the leaf.

epidermis

What are the products of photosynthesis?

C6H12O6, H2O, and O2

What colors of light absorbed by carotenoids?

blue-green & violet

A photosystem consists of a cluster of ______ molecules.

chlorophyll

In plants and algae, the proteins and chlorophyll molecules involved in the light-dependent reactions are ______.

embedded in the thylakoid membrane

Where are light-absorbing pigments found within chloroplasts?

embedded in the thylakoid membranes

What are the products of the light-dependent reactions?

oxygen, NADPH, ATP

After a key chlorophyll molecule transfers electrons to an electron acceptor, the electrons are

passed along a series of proteins in the thylakoid membrane.

High concentrations of O2 and low concentrations of CO2 in a leaf lead to ______, which undermines the Calvin cycle.

photorespiration

In ______, rubisco binds oxygen instead of carbon dioxide, and CO2 is the ultimate product, which is essentially the reverse of the Calvin cycle.

photorespiration

Which of the following describe the light-independent reactions?

ATP and NADPH are used in the stroma, Carbohydrates are produced, CO2 is used in the Calvin Cycle.

The primary wavelength of light that chlorophyll reflects is ______.

green

What are the are characteristics of the visible light spectrum?

intermediate wavelength, perceived by humans, absorbed by retinal, intermediate energy

What does it mean for a chlorophyll molecule to be "excited"?

its electrons are boosted to higher energy levels

The ______ consist of capturing energy from sunlight and using it to make ATP and NADPH.

light-dependent reactions

Chloroplasts are most numerous in which type of cells found in a leaf?

mesophyll

What cells in a leaf are the primary sites of photosynthesis?

mesophyll cells

Referring to the diagram, the cells that contain chloroplasts and are the sites of photosynthesis are called

mesophyll cells.

In C4 plants, carbon fixation occurs in ______, and the Calvin cycle occurs in ______.

mesophyll cells; bundle-sheath cells

ATP synthase is the only means for protons contained in the thylakoid space to ______.

move down their concentration gradient

Each "turn" of the Calvin cycle adds how many carbon atoms from carbon dioxide?

one

What type of light is reflected by carotenoids?

orange and yellow

In the C4 pathway, a carbon atom is first added to a three-carbon molecule to form a four-carbon molecule called ______, which is converted to ______ that can be used to regenerate CO2 for the C3 pathway.

oxaloacetate; malate

Light consists of tiny packets of energy called ______.

photons

During photosynthesis, the structure that consists of an arrangement of chlorophyll molecules that capture solar energy is called a ______.

photosystem

Chemiosmosis is the ______.

production of ATP fueled by the movement of hydrogen ions down their concentration gradient

The assembly of organic molecules from carbon dioxide is carried out by ______.

proteins and enzymes found in the stroma

Electrons that leave photosystem II are passed down an electron transport system and provide the energy to ______.

pump protons from the stroma to the thylakoid space

The openings in the epidermis of a leaf that allow the movement of CO2 and O2 into or out of the leaf are called ______.

stomata

Within the chloroplast, a semi-liquid substance called ______ fills the interior and contains enzymes that act to assemble organic molecules. Also present are numerous internal membranes called ______.

stroma; thylakoids

In C4 plants, carbon is first fixed and then transferred to bundle-sheath cells because ______.

the CO2 concentration can be built up in the bundle-sheath cells to favor the Calvin cycle

The assembly of new organic molecules occurs during a stage of photosynthesis called ______.

the Calvin cycle

What part of photosynthesis takes place in the stroma of chloroplasts?

the Calvin cycle

When an electron arrives at photosystem I from the first electron transport chain, what boosts the electron's energy to a very high energy level?

the absorption of another photon of light energy

The structure that gathers energy and sends it to a special chlorophyll a is ______

the antenna complex of the photosystem

During the light-dependent reactions, an excited electron is passed to a series of carrier molecules and proteins embedded in the thylakoid membrane called

the electron transport system.

What are produced by the steps of the Calvin cycle?

the five-carbon starting material, ADP, glyceraldehyde 3-phosphate

The ADP and NADP+ produced by the Calvin cycle are available to be used in

the light-dependent reactions.

NADPH and ATP are made during ______ and used during ______.

the light-dependent reactions; the Calvin cycle

What is the antenna complex?

the part of a photosystem that contains the pigment molecules

The key chlorophyll molecule that transfers an electron to an electron acceptor is called

the reaction center.

Where are the enzymes located that catalyze the reactions of the Calvin cycle?

the stroma

In the light-dependent reactions of photosynthesis, how many photosystems do plants and algae use in series?

two

Which of the following occur during the light-dependent reactions (the first two stages of photosynthesis)?

using energy to make ATP and NADPH, capturing energy from sunlight

The electromagnetic spectrum is the term used to describe the range of ______.

wavelengths and energy in sunlight

Photosynthesis primarily occurs in the ______ of a tree.

leaves

What is the role of the antenna complex in noncyclic photophosphorylation?

capture energy from photons and funnel it to the reaction center

The light-dependent reactions function to ______, while the light-independent reactions _______.

capture light energy; make glucose

What is the function of a photosystem?

capture photons of light energy

Given the following statements, choose the one that most closely describes the process of photosynthesis.

captures solar energy and makes it available to living organisms

The Calvin Cycle is a series of reactions that produces ______ from CO2 and the products of the light-dependent reactions.

carbohydrate molecules

The production of ATP fueled by the movement of hydrogen ions down their concentration gradient is called ______.

chemiosmosis

What are the products of the light-independent reactions that cycle back and are available for the light-dependent reactions?

ADP, NADP+

A proton gradient created by the electron transport chain can be used to make ______ in a process called chemiosmosis.

ATP

What is synthesized as protons pass through ATP synthase?

ATP

What molecules are made using the energy of electrons that pass down a series of proteins embedded in the thylakoid membrane?

ATP and NADPH

In what pathway does CO2 combine with a three-carbon molecule to produce a four-carbon molecule?

C4 photosynthesis

What are the reactants of photosynthesis?

CO2, H2O, and light energy

Which of the following is true about chlorophyll versus retinal?

Chlorophyll is more efficient at capturing photons.

_______________ are the site of photosynthesis and are located in the mesophyll cells of the plant's leaves.

Chloroplast

Why is noncyclic photophosphorylation called "noncyclic"?

Electrons that are ejected from photosystems do not return to them.

How does chlorophyll function in photosynthesis?

It absorbs energy from light.

What happens to the four-carbon molecule produced by the C4 pathway?

It is used to regenerate CO2, which can then enter the Calvin cycle.

What is needed for the production of NADPH in photosynthesis?

NADP+, H+, electrons

What is true about the electron that reaches photosystem I from photosystem II?

The electron still has around 50% of its boosted energy, The electron receives another boost of energy from a photon.

What key event represents the capture of energy from the sun?

The electrons of a chlorophyll molecule are boosted to higher energy levels.

Which are true about photosystems.?

They act as antennae for capturing light energy, Chlorophyll molecules are arranged in a precise pattern, & Chlorophyll molecules are held in a specific location by proteins.

Which are true about chlorophyll a and b?

They capture photons with a magnesium ion, & They differ slightly in their chemical side groups.

The thylakoid membranes shown here occur within chloroplasts and

are all connected but function more or less independently.

What is a group of accessory pigment molecules in plants that absorb violet to blue-green light?

carotenoids

From which photosystem(s) are excited electrons transferred to an electron transport chain?

both photosystem I and photosystem II

Plants that overcome photorespiration by isolating different chemical reactions in different types of cells are ______

c4 plants

Carbon _______________ is the process of converting gaseous carbon dioxide into an organic carbon molecule.

fixation

C4 plants are able to overcome the effects of photorespiration by ______.

fixing carbon through different chemical reactions in different cells

Carbon fixation is the process where a carbon atom ______.

from carbon dioxide is added to an organic molecule

The antenna complex in a photosystem ______.

funnels energy to a special chlorophyll a

What conditions in the leaf lead to an increase in photorespiration and a decrease in the successful performance of the Calvin cycle?

high concentrations of O2 and low concentrations of CO2

The enzymes and other proteins that are found in the stroma of the chloroplast function ______.

in the assembly of organic molecules

Photorespiration is the term used to describe when ______.

rubisco binds oxygen and the reverse of the Calvin cycle takes place

How many turns of the Calvin cycle are needed to produce one six carbon sugar like glucose?

six