Biology 1001-Ch. 7

Which step of the Calvin cycle requires no extra energy?
– chemiosmosis of ATP
– generation of G3P
– generation of NADPH
– splitting of water
– carbon fixation by rubisco
– regeneration of RuBP

carbon fixation by rubisco This process requires no energy carriers to be expended

Carbon fixation involves the addition of carbon dioxide to _____.
– Rubisco
– NADPH
– G3P
– RuBP
– 3-PGA

RuBP In the Calvin cycle, carbon dioxide is added to RuBP.

After 3-PGA is phosphorylated, it receives energized electrons from _____.
– NADPH
– NADP+
– ADP
– CO2
– ATP

NADPH NADPH supplies the electrons that reduce the phosphorylated 3-PGA.

How many carbon dioxide molecules must be added to RuBP to make a single molecule of glucose?
– 2
– 10
– 4
– 8
– 6

6 Six carbon dioxide molecules are required to produce two G3P molecules, which can be combined to make one glucose molecule.

In the Calvin cycle, how many ATP molecules are required to regenerate RuBP from five G3P molecules?
– 2
– 4
– 5
– 3
– 1

3

Which of the following leaf types would be the most efficient at absorbing sunlight?
– Large, broad leaves
– Needlelike leaves
– All of these leaf types are equally efficient at absorbing sunlight.
– Small, narrow leaves

Large, broad leaves These leaves have a large surface area and would be able to most efficiently absorb sunlight.

Which of the following structures allows for gas exchange between the tissues of a leaf and the atmosphere?
– Vascular bundle
– Stomata
– Cuticle
– Epidermis

Stomata on the underside of the leaf control the passage of gases into and out of the leaf.

True or false. Guard cells open during the day to allow gases to flow through the stomata.
– True
– False

True During the day, sunlight causes the guard cells to engorge with water, which causes the cells to bow apart and opens the stomata.

Your teacher wants you to mix up the enzymes and substrates necessary to perform the Calvin cycle in a test tube. In order to control the reactions, you wish to do this in the absence of the light reactions, whole chloroplasts, and cells. What components do you need to put into the test tube?
– ATP, NADPH, and an extract from chloroplast stroma
– ATP, NADPH, and CO2
– ATP, CO2, and an extract from chloroplast stroma
– ATP, CO2, and intact thylakoids
– ATP, CO2, NADPH, and a light source
– ATP, NADPH, and intact thylakoids

ATP, NADPH, and an extract from chloroplast stroma The enzymes of the stroma need ATP and NADPH to perform the Calvin cycle. CO2 is available in the air.

What is the purpose of a cuticle on a leaf?
– to perform photosynthesis
– to carry water to the rest of the leaf
– to prevent water loss
– to allow CO2 to enter the cell
– to bring in more light
– to carry sugar down to the roots

to prevent water loss The wax cuticle makes the leaf waterproof, to prevent water from leaving by evaporation. The oil on your skin performs a similar function.

Which of the following equations represents photosynthesis?
– C6H12O6 + 6O2 → 6CO2 + 6H2O
– 6CO2 + 6O2 → C6H12O6 + 6H2O
– 6CO2 + 6H2O → C6H12O6 + 6O2
– C6H12O6 + 6CO2 → 6O2 + 6H2O
– 6H2O + 6O2 → C6H12O6 + 6CO2

6CO2 + 6H2O → C6H12O6 + 6O2 Photosynthesis requires carbon dioxide and water for the production of sugar and oxygen.

In which of the following organelles does photosynthesis take place?
– Mitochondrion
– Ribosome
– Central vacuole
– Chloroplast
– Nucleus

Chloroplast Chloroplasts use energy from light to transform carbon dioxide and water into sugar and oxygen.

What connects the two photosystems in the light reactions?
– Chlorophyll
– The Calvin cycle
– An electron transport chain
– A thylakoid
– A chain of glucose molecules

An electron transport chain An electron transport chain connects the two photosystems in the light reactions.

What two molecules are produced by the light reactions and used to power the Calvin cycle?
– G3P and H2O
– C6H12O6 and RuBP
– ATP and NADPH
– CO2 and O2
– C6H12O6 and O2

ATP and NADPH ATP and NADPH are both products of the light reactions and are used to power the Calvin cycle.

What provides electrons for the light reactions?
– Light
– O2
– H2O
– CO2
– The Calvin cycle

H2O Electrons are stripped from water in the light reactions of photosynthesis. This is one of the reasons plants need water.

What provides the carbon atoms that are incorporated into sugar molecules in the Calvin cycle?
– Carbon dioxide (CO2)
– RuBP
– Glucose (C6H12O6)
– G3P (C3H6O3)
– Sucrose (C12H22O11)

Carbon dioxide provides the carbon atoms that are incorporated into sugars in photosynthesis. This is why plants need to take in carbon dioxide.

What transports electrons from the light reactions to the Calvin cycle?
– FADH2
– NADH
– An electron transport chain
– Chlorophyll
– NADPH

NADPH is an electron carrier that picks up electrons in the light reactions and releases them in the Calvin cycle.

The light reactions take place in the _________ and the Calvin cycle takes place in the _________.
– chloroplasts; mitochondria
– stroma; thylakoids
– mitochondria; chloroplasts
– thylakoids; stroma
– inner membrane; outer membrane

Within the chloroplast, the light reactions take place in the flattened sacs called thylakoids and the Calvin cycle takes place in the thick fluid called the stroma.

Where is the most energy used in the Calvin cycle?
– in the regeneration of RuBP
– in the rearrangement of the six-carbon molecule made from RuBP and CO2 into the three-carbon molecules of PGA
– in the fixation of CO2 to RuBP
– in the linkage of two G3P molecules together to form glucose
– in the conversion of PGA to G3P

in the conversion of PGA to G3P Creating the higher-energy bonds in G3P requires the most energy in the Calvin cycle.

How is the energy present in the electrons passed through electron transport chain II first used?
– The energy is trapped in the bonds between NADP+ and H+.
– The energy is used to pump hydrogen ions into the thylakoid space.
– The energy is used to split water and create hydrogen ions.
– The energy is used to pump hydrogen ions into the stroma.
– The energy is trapped in the bonds between ADP and P.
– The energy is used to pump electrons into the stroma.

The energy is used to pump hydrogen ions into the thylakoid space. In this small space, it is easy to create a concentration gradient of hydrogen ions. If ions were instead pumped into the stroma, it would take many more ions to create a chemiosmotic force.

The light reactions of photosynthesis use _____ and produce _____.
– NADPH … NADP+
– carbon dioxide … sugar
– NADPH … oxygen
– water … NADPH
– carbon dioxide … oxygen

water … NADPH During the light reactions, water is split to produce oxygen. Excited electrons from water join with NADP+ to produce NADPH.

Why do plant leaves appear green?
– The chlorophyll in the leaves uses green light.
– The chlorophyll in the leaves transmits green light.
– The chlorophyll in the leaves transforms light of other wavelengths into green light.
– The chlorophyll in leaves reflects green light.
– The chlorophyll in the leaves changes shape when struck by green light.
– The chlorophyll in the leaves absorbs green light.

The chlorophyll in leaves reflects green light. Objects appear to be the color they reflect the most.

In what order do the steps of the light reactions occur?
– electron transport chain II, photosystem II, electron transport chain I, photosystem I
– photosystem II, photosystem I, electron transport chain II, electron transport chain I
– photosystem II, electron transport chain II, photosystem I, electron transport chain I
– electron transport chain I, photosystem I, electron transport chain II, photosystem II
– photosystem I, electron transport chain I, photosystem II, electron transport chain II
– photosystem I, photosystem II, electron transport chain I, electron transport chain II

photosystem II, electron transport chain II, photosystem I, electron transport chain I Photosystem I was discovered first, but it does not occur first.

How many molecules of carbon are fixed in each round of the Calvin cycle?
– 3
– 15
– 1
– 5
– 6

3 Glyceraldehyde-3-phosphate, a three-carbon molecule, is the product of this cycle.

Chlorophyll a can absorb well in both the violet/blue end of the spectrum and the orange/red end of the spectrum. Why then is ultraviolet light considered a very good source of energy for photosynthesis?
– Chlorophyll b absorbs better in the violet/blue wavelengths.
– Ultraviolet light has more energy per photon.
– The sun produces more photons with a violet/blue wavelength than with a red wavelength.
– Chlorophyll b reflects orange/red light away from chlorophyll a.
– Carotenoids absorb better in the violet/blue wavelengths as well.

Ultraviolet light has more energy per photon. Photons of ultraviolet wavelengths carry more energy than those of the visible wavelengths.

Which cell type in a leaf performs the most photosynthesis?
– mesophyll
– stem
– epidermis
– bundle sheath
– stomata

mesophyll The mesophyll cells in the middle of the leaf perform the most photosynthesis.

Where are the electrons used in photosystem II found at the very end of the light reactions?
– in the stroma
– in NADPH
– in photosystem I
– in ATP
– in chlorophyll

in NADPH The electrons and a few of the hydrogen ions released from water in photosystem II are bound to NADP+ to form molecules of NADPH.

_____ has a longer wavelength than _____.
– Yellow … red
– Blue … green
– Green … yellow
– Red … green
– Violet … blue

Red has a longer wavelength than green.

When discussing photosynthesis, some people mistakenly talk about the light reactions and the dark reactions. Why is "dark reactions" an inaccurate name for the Calvin cycle?
– The light reactions occur on the outside of a chloroplast and the Calvin cycle occurs in the center of the chloroplast.
– This implies that the Calvin cycle occurs only at night.
– It does not give proper credit to the scientist who discovered carbon fixation in photosynthesis.
– Dark reactions is another name for photorespiration.
– Both the light reactions and the Calvin cycle are dependent on light.

This implies that the Calvin cycle occurs only at night.

You place a plant in a transparent box made of greenish-yellow plastic. How does this affect photosynthesis for the plant?
– Only pigments that appear greenish-yellow will be able to absorb the light. Photosynthesis will be slowed.
– The orange carotenoids would absorb light of this wavelength. Photosynthesis will proceed unchanged.
– Only chlorophyll b will be able to absorb the light. Photosynthesis will proceed unchanged.
– All of the plant pigments will be able to absorb the light, but this light is lower energy. Photosynthesis will be slowed.
– None of the plant pigments will be able to absorb the light. Photosynthesis will stop.

None of the plant pigments will be able to absorb the light. Photosynthesis will stop.

Which of the following summarizes photosystem I and the electron transport chain I in terms of exergonic and endergonic reactions.
– The energy of sunlight is used to power the exergonic reaction of combining ADP with P.
– The energy of sunlight is used to power the endergonic reaction of combining NADP+ with H+.
– The energy of sunlight is used to power the endergonic reaction of combining ADP with P.
– The energy of the electron from photosystem II is used to power the exergonic reaction of combining NADP+ with H+.
– The energy of sunlight is used to power the exergonic reaction of combining NADP+ with H+.
– The energy of the electron from photosystem II is used to power the endergonic reaction of combining NADP+ with H+.

The energy of sunlight is used to power the endergonic reaction of combining ADP with P.

Why do plants produce O2?
– because O2 is produced as a by-product when the plant creates H+ ions and free electrons from water
– because O2 is produced as a by-product when the plant removes the carbon from CO2
– because O2 is produced as a by-product when the plant creates H+ ions and water
– because O2 is produced by the plant for later use during the Calvin cycle
– because O2 is produced by the plant for later use during respiration

because O2 is produced as a by-product when the plant creates H+ ions and free electrons from water

How is O2 involved in photosynthesis?
– O2 is a product in the dark reactions.
– O2 is a reactant in the dark reactions.
– O2 is a product in the Calvin cycle.
– O2 is a reactant in the light reactions.
– O2 is a reactant in the Calvin cycle.
– O2 is a product of the light reactions.

O2 is a product of the light reactions.

Which of the following is most similar to the Calvin cycle?
– a human breathing in oxygen and breathing out carbon dioxide
– a solar panel converting sunlight into electricity
– a tree that is on fire
– a robot assembling a car
– a loaf of bread in the oven
– a farmer harvesting grain in the fall

a robot assembling a car

Which of the following describes the steps of photosystem II and electron transport chain II in terms of energy conversions?
– Kinetic energy from sunlight is converted into potential energy in an electron. The potential energy of the electron is converted to potential energy in NADPH.
– Potential energy from the sun is converted into potential energy in an electron. The potential energy of the electron is converted to potential energy in NADPH.
– Kinetic energy from sunlight is converted into potential energy in an electron. This then is converted to kinetic energy by pumping hydrogen ions. The kinetic energy of the ions flowing back through the membrane is converted to potential energy in ATP.
– Potential energy from sunlight is converted into potential energy in an electron. This then is converted to kinetic energy by pumping hydrogen ions. The kinetic energy of the ions flowing back through the membrane is converted to potential energy in NADPH.
– Kinetic energy from sunlight is converted into kinetic energy in an electron. This then is converted to potential energy in ATP.
– Kinetic energy from sunlight is converted to potential energy by pumping hydrogen ions. The kinetic energy of the ions flowing back through the membrane is converted to kinetic energy in ATP.

Kinetic energy from sunlight is converted into potential energy in an electron. This then is converted to kinetic energy by pumping hydrogen ions. The kinetic energy of the ions flowing back through the membrane is converted to potential energy in ATP.

Why do chloroplasts make energy carriers during the light reactions?
– to capture the energy of sugar when it is broken down
– to capture the energy of sunlight
– to provide energy for the synthesis of sugar
– to create oxygen for the synthesis of sugar
– to do work in the entire cell

to provide energy for the synthesis of sugar