Understanding Photosynthesis: Light Reactions and the Calvin Cycle

Biology

9th Grade,
10th Grade,
11th Grade,
12th Grade

NGSS

Reviewed by Editorial Team

The ProProfs editorial team is comprised of experienced subject matter experts. They've collectively created over 10,000 quizzes and lessons, serving over 100 million users. Our team includes in-house content moderators and subject matter experts, as well as a global network of rigorously trained contributors. All adhere to our comprehensive editorial guidelines, ensuring the delivery of high-quality content.

Learn about Our Editorial Process

| By Thames

Thames

Community Contributor

Quizzes Created: 7682 | Total Attempts: 9,547,133

| Attempts: 17 | Questions: 15 | Updated: Aug 4, 2025

Quiz Flashcard

Share on Facebook Share on Twitter Share on Whatsapp Share on Pinterest Share on Email Copy to Clipboard Embed on your website

Question 1 / 15

0 %

0/100

Score 0/100

1. Summarize reactions occurring in the three phases of the Calvin cycle.

Fixation: -carbon is fixed out of the atmosphere by rubisco to a 5 carbon RuBP molecules -it is broken into... Fixation: -carbon is fixed out of the atmosphere by rubisco to a 5 carbon RuBP molecules -it is broken into 2 3-Carbon atoms (3-phosphoglycerate)Reduction:-add ATP and NADPH to create G3P which goes on to become glucose or used for regeneration Regeneration: G3P regenerated by RuBP (requires ATP)

Photosynthesis converts sunlight into heat energy.

Glycolysis is the main process involved in the Calvin cycle.

The Calvin cycle involves the conversion of carbon dioxide into oxygen.

Submit

About This Quiz

Explore the essential biological process of photosynthesis, where plants convert sunlight into energy. This quiz enhances understanding of the light-dependent reactions and the Calvin cycle, crucial for students in biology, emphasizing practical applications and relevance in natural sciences.

2. What first name or nickname would you like us to use?

You may optionally provide this to label your report, leaderboard, or certificate.

2. Why is RUBISCO considered the most important enzyme on earth?

Because it produces oxygen as a byproduct of its reaction

Because it fixates carbon out of the air -one of least efficient enzyme

Because it helps in breaking down glucose for energy production

Because it plays a key role in DNA replication and repair

RUBISCO is crucial for photosynthesis as it catalyzes the first major step in carbon fixation, converting atmospheric carbon dioxide into organic compounds. This process is essential for the survival of plants and other autotrophic organisms, making RUBISCO critically important for life on earth.

Explanation

Submit

3. What does fixed mean?

Fastening two things together

Repairing a broken object

Adjusting a malfunctioning device

Extracting Carbon Dioxide and putting it in a usable form

The term 'fixed' in this context specifically refers to the process of extracting Carbon Dioxide and converting it into a usable form, rather than the general sense of fixing or repairing something physical.

Explanation

Submit

4. In what two ways does photorespiration drain energy from the plant?

1. Decreases energy consumption 2. Enhances carbon fixation

1. Generates energy 2. Increases fixed carbon stores

1. Requires no energy 2. Promotes carbon retention

1. Uses energy2. Loss of Fixed carbon

Photorespiration in plants is a process that uses energy and results in the loss of fixed carbon, ultimately reducing the efficiency of photosynthesis.

Explanation

Photorespiration in plants is a process that uses energy and results in the loss of fixed carbon, ultimately reducing the efficiency of photosynthesis.

Submit

5. Describe the pathway of gasses from the atmosphere to the interior of a leaf.

Gasses are transported through the roots and stems of the plant before reaching the leaf interior.

Gasses enter the leaf through tiny openings called chloroplasts.

Gasses are absorbed directly through the leaf surface by the epidermal cells.

Atmosphere gases go through the stomata into the air space where the mesophyll cells fix carbon out of the atmosphere

The correct pathway involves gasses entering through the stomata and diffusing into the air spaces within the leaf to be absorbed by mesophyll cells. The other options do not accurately describe the process of gas exchange in leaves.

Explanation

Submit

6. What are the advantages and disadvantages to a plant of opening and closing stomata?

OPEN: gain carbon dioxide, lose oxygen (PRO), gain water (CON) CLOSING: not gain carbon dioxide, don't lose oxygen (CON), don't... OPEN: gain carbon dioxide, lose oxygen (PRO), gain water (CON) CLOSING: not gain carbon dioxide, don't lose oxygen (CON), don't gain water (PRO)

OPEN:-gain carbon dioxide-lose oxygen (PRO)-lose water (CON)CLOSING-not gain carbon dioxide-don't lose oxygen (CON)-don't lose water (PRO)

OPEN: lose carbon dioxide, lose oxygen (CON), gain water (CON) CLOSING: not lose carbon dioxide, don't lose oxygen (CON), don't... OPEN: lose carbon dioxide, lose oxygen (CON), gain water (CON) CLOSING: not lose carbon dioxide, don't lose oxygen (CON), don't gain water (PRO)

OPEN: lose carbon dioxide, gain oxygen (CON), gain water (CON) CLOSING: not lose carbon dioxide, don't gain oxygen (CON), don't... OPEN: lose carbon dioxide, gain oxygen (CON), gain water (CON) CLOSING: not lose carbon dioxide, don't gain oxygen (CON), don't gain water (PRO)

Opening stomata allows a plant to gain carbon dioxide for photosynthesis but may lead to water loss. Closing stomata prevents the entry of carbon dioxide but also prevents water loss.

Explanation

Opening stomata allows a plant to gain carbon dioxide for photosynthesis but may lead to water loss. Closing stomata prevents the entry of carbon dioxide but also prevents water loss.

Submit

7. What happens to the sugar that is produced by photosynthesis?

1. Respiration2. used in cell walls/cellulose3. storage4. structure

1. Excretion2. Fermentation3. Photosynthesis

Sugar produced by photosynthesis can be used in various ways such as in respiration, as a component of cell walls, for storage, and as a structural component.

Explanation

Sugar produced by photosynthesis can be used in various ways such as in respiration, as a component of cell walls, for storage, and as a structural component.

Submit

8. What is the process involved in C4 photosynthesis?

-CO2 air and O2 come in -fixed in guard cells by ATP synthase-through transpiration into stomata-go through cytoplasm where C4... -CO2 air and O2 come in -fixed in guard cells by ATP synthase-through transpiration into stomata-go through cytoplasm where C4 is converted to C3-C3 transported to phloem-CO2 goes to roots where it is converted to glucose INVOLVES WATER ABSORPTION.

-CO2 air and O2 come in -fixed in stomata by rubisco-through vascular bundles in leaf-go through chloroplasts where C4 is... -CO2 air and O2 come in -fixed in stomata by rubisco-through vascular bundles in leaf-go through chloroplasts where C4 is converted to C3-C3 degraded-CO2 goes to mitochondria where it is converted to ATP PRODUCES LESS OXYGEN.

-CO2 air and O2 come in -fixed in mesophyll by pep carboxylase-through plasmodesmata into bundle sheath-go through mitochondria where C4... -CO2 air and O2 come in -fixed in mesophyll by pep carboxylase-through plasmodesmata into bundle sheath-go through mitochondria where C4 is converted to C3-C3 regenerated-CO2 goes to chloroplasts where it is converted to starch FIXES MORE CARBON

-N2 air and H2O come in -fixed in roots by nitrogenase-through xylem into leaves-go through vacuoles where C4 is converted... -N2 air and H2O come in -fixed in roots by nitrogenase-through xylem into leaves-go through vacuoles where C4 is converted to C3-C3 transported back to roots where it is converted to amino acids NITROGEN IS FIXATED.

C4 photosynthesis involves a series of steps where carbon dioxide and oxygen are processed through different cellular components to ultimately fix more carbon compared to C3 photosynthesis. The correct answer details the specific process in C4 photosynthesis, while the incorrect answers inaccurately describe different processes related to photosynthesis.

Explanation

Submit

9. Explain the process of CAM photosynthesis.

-CAM plants store carbon as glucose during the night.

-stomata open at night and closed during the day -fixes carbon at night-PEP Carboxylase -C4 goes into vacuole where it... -stomata open at night and closed during the day -fixes carbon at night-PEP Carboxylase -C4 goes into vacuole where it is stored until day time-C4 is converted to C3 -CO2 goes to chloroplasts where it is converted to starch prevents water loss by stomata being open at night

-Photosynthesis occurs only during the day.

-C3 plants have a different mechanism for fixing carbon dioxide.

CAM (Crassulacean Acid Metabolism) is a unique carbon fixation pathway that allows certain plants to minimize water loss by opening their stomata at night to take in carbon dioxide. The correct answer explains the whole process of CAM photosynthesis, while the incorrect answers provide misleading information or characteristics of other types of photosynthesis.

Explanation

Submit

10. Where does the light reaction and Calvin Cycle take place in the chloroplast?

Grana--Light Reaction, Mitochondria--Calvin Cycle

Extra membrane to allow for gradient Thylakoid--Light ReactionStroma-- Calvin Cycle

Outer membrane--Light Reaction, Inner membrane--Calvin Cycle

Chlorophyll--Light Reaction, ATP Synthase--Calvin Cycle

The thylakoid membrane is where the light reaction takes place, while the stroma is where the Calvin Cycle occurs within the chloroplast. The other options do not accurately reflect the locations where these processes occur in a chloroplast.

Explanation

Submit

11. In C4 and CAM plants, does rubisco always operate under conditions of elevated CO2?

In C4 and CAM plants rubisco always operates under conditions of elevated CO2

No, rubisco in C4 and CAM plants does not require CO2 for its function.

No, rubisco in C4 and CAM plants operates efficiently under regular atmospheric CO2 levels.

No, rubisco in C4 and CAM plants operates under low CO2 conditions.

Rubisco in C4 and CAM plants is adapted to function under conditions of elevated CO2 to prevent photorespiration and increase efficiency of carbon fixation.

Explanation

Rubisco in C4 and CAM plants is adapted to function under conditions of elevated CO2 to prevent photorespiration and increase efficiency of carbon fixation.

Submit

12. Predict the relative success of C3, C4 and CAM plants in a cool, wet environment vs. hot, dry environment.

C3: ok in cool, wet environments, but good in hot, dry environments. C4: good in cool, wet environments, but ok... C3: ok in cool, wet environments, but good in hot, dry environments. C4: good in cool, wet environments, but ok in hot, dry environments. CAM: good in cool, wet environments, but bad in hot, dry environments.

C3: good in cool, wet environments, but bad in hot, dry environments. C4: good in cool, wet environments, but bad... C3: good in cool, wet environments, but bad in hot, dry environments. C4: good in cool, wet environments, but bad in hot, dry environments. CAM: bad in cool, wet environments, but good in hot, dry environments.

C31. good 2. good3. badC41. ok (less good-requires energy)2. ok (less good-requires energy)3. goodCAM1. ok (less good-requires energy)2. ok (less... C31. good 2. good3. badC41. ok (less good-requires energy)2. ok (less good-requires energy)3. goodCAM1. ok (less good-requires energy)2. ok (less good-requires energy)3. good

C3: good in cool, wet environments, but bad in hot, dry environments. C4: bad in cool, wet environments, but good... C3: good in cool, wet environments, but bad in hot, dry environments. C4: bad in cool, wet environments, but good in hot, dry environments. CAM: good in cool, wet environments, but bad in hot, dry environments.

C3 plants are more successful in hot, dry environments due to their ability to efficiently capture and use CO2 during photosynthesis. C4 plants are better adapted to hot, dry conditions as they have a specialized mechanism for concentrating CO2 in their cells. CAM plants perform well in hot, dry environments by opening their stomata at night to reduce water loss and carrying out photosynthesis during the day.

Explanation

Submit

13. How does the current atmosphere differ from that in which photosynthesis evolved? How does the earth atmosphere reduce the efficiency of rubisco?

Oxygen levels used to be much lower and CO2 levels used to be much higherSwitched-as CO2 dropped that is when... Oxygen levels used to be much lower and CO2 levels used to be much higherSwitched-as CO2 dropped that is when photosynthesis evolved Because oxygen can fit into binding site of rubisco reduces the efficiency--uses oxygen instead of CO2 which competes at enzymes active sites which slows the rate of CO2 reduction HAD TO EVOLVE WAYS TO AVOID PHOTORESPIRATION ( fixated oxygen not carbon)

Photosynthesis developed in an atmosphere with similar oxygen and CO2 levels as the current atmosphere. Rubisco's inefficiency is solely caused... Photosynthesis developed in an atmosphere with similar oxygen and CO2 levels as the current atmosphere. Rubisco's inefficiency is solely caused by the lack of available carbon dioxide in the current atmosphere.

The current atmosphere has higher CO2 levels and lower oxygen levels than when photosynthesis evolved. Rubisco's efficiency is reduced by... The current atmosphere has higher CO2 levels and lower oxygen levels than when photosynthesis evolved. Rubisco's efficiency is reduced by the lack of oxygen, causing a decrease in CO2 fixation.

During the evolution of photosynthesis, the atmosphere had much higher levels of oxygen and lower CO2 levels. Rubisco's inefficiency in... During the evolution of photosynthesis, the atmosphere had much higher levels of oxygen and lower CO2 levels. Rubisco's inefficiency in the current atmosphere is due to excess CO2 competing with oxygen at its active sites.

Submit

14. C4 and CAM photosynthesis are described as "CO2 pumps". How do these forms of photosynthesis differ from C3 and why should they be characterized as "pumps"?

C4 and CAM photosynthesis pump in more water than C3 photosynthesis.

C4 and CAM photosynthesis release more oxygen but less carbohydrates compared to C3 photosynthesis.

C4 and CAM photosynthesis are only found in aquatic plants, unlike C3 photosynthesis that is found in terrestrial plants.

Function as pumps to minimize the amount of photorespiration that occurs when stomata are closed and CO2 cannot diffuse directly... Function as pumps to minimize the amount of photorespiration that occurs when stomata are closed and CO2 cannot diffuse directly from atmosphere-process is different and how CO2 is moved through cell different and when its allowed to move into cell

C4 and CAM photosynthesis are characterized as 'CO2 pumps' because they function to minimize photorespiration, which occurs when stomata are closed and CO2 cannot diffuse directly from the atmosphere. The process of moving CO2 through the cell is different in C4 and CAM photosynthesis compared to C3, and these mechanisms allow for more efficient CO2 uptake.

Explanation

Submit

15. At the end of the light reaction, where is the energy derived from the photons stored?

Released as heat energy

Conducted to the Calvin cycle

Stored in glucose

Stored as NADPH and ATP

During the light reaction of photosynthesis, energy from photons is used to create NADPH and ATP, which are then utilized in the Calvin cycle to produce glucose.

Explanation

During the light reaction of photosynthesis, energy from photons is used to create NADPH and ATP, which are then utilized in the Calvin cycle to produce glucose.

Submit