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
answer
carbon fixation by rubisco
This process requires no energy carriers to be expended
question
Carbon fixation involves the addition of carbon dioxide to _____.
- Rubisco
- NADPH
- G3P
- RuBP
- 3-PGA
answer
RuBP
In the Calvin cycle, carbon dioxide is added to RuBP.
question
After 3-PGA is phosphorylated, it receives energized electrons from _____.
- NADPH
- NADP+
- ADP
- CO2
- ATP
answer
NADPH
NADPH supplies the electrons that reduce the phosphorylated 3-PGA.
question
How many carbon dioxide molecules must be added to RuBP to make a single molecule of glucose?
- 2
- 10
- 4
- 8
- 6
answer
6
Six carbon dioxide molecules are required to produce two G3P molecules, which can be combined to make one glucose molecule.
question
In the Calvin cycle, how many ATP molecules are required to regenerate RuBP from five G3P molecules?
- 2
- 4
- 5
- 3
- 1
answer
3
question
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
answer
Large, broad leaves
These leaves have a large surface area and would be able to most efficiently absorb sunlight.
question
Which of the following structures allows for gas exchange between the tissues of a leaf and the atmosphere?
- Vascular bundle
- Stomata
- Cuticle
- Epidermis
answer
Stomata on the underside of the leaf control the passage of gases into and out of the leaf.
question
True or false. Guard cells open during the day to allow gases to flow through the stomata.
- True
- False
answer
True
During the day, sunlight causes the guard cells to engorge with water, which causes the cells to bow apart and opens the stomata.
question
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
answer
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.
question
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
answer
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.
6CO2 + 6H2O → C6H12O6 + 6O2
Photosynthesis requires carbon dioxide and water for the production of sugar and oxygen.
question
In which of the following organelles does photosynthesis take place?
- Mitochondrion
- Ribosome
- Central vacuole
- Chloroplast
- Nucleus
answer
Chloroplast
Chloroplasts use energy from light to transform carbon dioxide and water into sugar and oxygen.
question
What connects the two photosystems in the light reactions?
- Chlorophyll
- The Calvin cycle
- An electron transport chain
- A thylakoid
- A chain of glucose molecules
answer
An electron transport chain
An electron transport chain connects the two photosystems in the light reactions.
question
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
answer
ATP and NADPH
ATP and NADPH are both products of the light reactions and are used to power the Calvin cycle.
question
What provides electrons for the light reactions?
- Light
- O2
- H2O
- CO2
- The Calvin cycle
answer
H2O
Electrons are stripped from water in the light reactions of photosynthesis. This is one of the reasons plants need water.
question
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)
answer
Carbon dioxide provides the carbon atoms that are incorporated into sugars in photosynthesis. This is why plants need to take in carbon dioxide.
question
What transports electrons from the light reactions to the Calvin cycle?
- FADH2
- NADH
- An electron transport chain
- Chlorophyll
- NADPH
answer
NADPH is an electron carrier that picks up electrons in the light reactions and releases them in the Calvin cycle.
question
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
answer
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.
question
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
answer
in the conversion of PGA to G3P
Creating the higher-energy bonds in G3P requires the most energy in the Calvin cycle.
question
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.
answer
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.
question
The light reactions of photosynthesis use _____ and produce _____.
- NADPH ... NADP+
- carbon dioxide ... sugar
- NADPH ... oxygen
- water ... NADPH
- carbon dioxide ... oxygen
answer
water ... NADPH
During the light reactions, water is split to produce oxygen. Excited electrons from water join with NADP+ to produce NADPH.
question
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.
answer
The chlorophyll in leaves reflects green light.
Objects appear to be the color they reflect the most.
question
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
answer
photosystem II, electron transport chain II, photosystem I, electron transport chain I
Photosystem I was discovered first, but it does not occur first.
question
How many molecules of carbon are fixed in each round of the Calvin cycle?
- 3
- 15
- 1
- 5
- 6
answer
3
Glyceraldehyde-3-phosphate, a three-carbon molecule, is the product of this cycle.
question
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.
answer
Ultraviolet light has more energy per photon.
Photons of ultraviolet wavelengths carry more energy than those of the visible wavelengths.
question
Which cell type in a leaf performs the most photosynthesis?
- mesophyll
- stem
- epidermis
- bundle sheath
- stomata
answer
mesophyll
The mesophyll cells in the middle of the leaf perform the most photosynthesis.
question
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
answer
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.
question
_____ has a longer wavelength than _____.
- Yellow ... red
- Blue ... green
- Green ... yellow
- Red ... green
- Violet ... blue
answer
Red has a longer wavelength than green.
question
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.
answer
This implies that the Calvin cycle occurs only at night.
question
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.
answer
None of the plant pigments will be able to absorb the light. Photosynthesis will stop.
question
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+.
answer
The energy of sunlight is used to power the endergonic reaction of combining ADP with P.
question
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
answer
because O2 is produced as a by-product when the plant creates H+ ions and free electrons from water
question
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.
answer
O2 is a product of the light reactions.
question
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
answer
a robot assembling a car
question
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.
answer
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.
question
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
answer
to provide energy for the synthesis of sugar
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