Unique Photosynthetic Pigment Quiz

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Organism Quizzes & Trivia

Photosynthesis is the process through which plants use sunlight to get nutrients from carbon dioxide and water. The pigment that is present in chloroplasts that captures the light energy necessary for photosynthesis is what referred to as a photosynthesis pigment is. The quiz below is designed to test out how much you know about this pigment. Give it a shot and see how high you score and keep an eye out for more quizzes.


Questions and Answers
  • 1. 

    If photosynthesising green algae are provided with CO2 synthesised with heavy oxygen (18O), later analysis will show that all but one of the following compounds produced by the algae contain the 18O label. That one is

    • A.

      RuBP

    • B.

      Glucose

    • C.

      PGAL.

    • D.

      PGA.

    • E.

      O2.

    Correct Answer
    E. O2.
    Explanation
    When photosynthesising green algae are provided with CO2 synthesised with heavy oxygen (18O), the oxygen from CO2 is incorporated into the organic compounds produced during photosynthesis. This means that all organic compounds except one will contain the 18O label. Oxygen gas (O2) is not produced directly from the incorporation of CO2 into organic compounds during photosynthesis, so it will not contain the 18O label. Therefore, the correct answer is O2.

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  • 2. 

    Which of the following are products of the light reactions of photosynthesis that are utilized in the Calvin cycle?

    • A.

      ATP and NADPH

    • B.

      Electrons and H+

    • C.

      CO2 and glucose

    • D.

      H2O and O2

    • E.

      ADP, Pi, and NADP+

    Correct Answer
    A. ATP and NADPH
    Explanation
    The products of the light reactions of photosynthesis that are utilized in the Calvin cycle are ATP and NADPH. These molecules provide the energy and reducing power, respectively, necessary for the Calvin cycle to synthesize glucose from carbon dioxide.

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  • 3. 

    What are the products of the light reactions that are subsequently used by the Calvin cycle?

    • A.

      Oxygen and carbon dioxide

    • B.

      Water and carbon

    • C.

      Carbon dioxide and RuBP

    • D.

      Electrons and photons

    • E.

      ATP and NADPH

    Correct Answer
    E. ATP and NADPH
    Explanation
    The products of the light reactions, ATP and NADPH, are subsequently used by the Calvin cycle. ATP provides the energy needed for the Calvin cycle to convert carbon dioxide into glucose, while NADPH provides the electrons necessary for the reduction of carbon dioxide. Therefore, ATP and NADPH are essential in the production of glucose during the Calvin cycle.

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  • 4. 

    Where does the Calvin cycle take place?

    • A.

      Cytoplasm surrounding the chloroplast

    • B.

      Outer membrane of the chloroplast

    • C.

      Chlorophyll molecule

    • D.

      Thylakoid membrane

    • E.

      Stroma of the chloroplast

    Correct Answer
    E. Stroma of the chloroplast
    Explanation
    The Calvin cycle takes place in the stroma of the chloroplast. This is where the reactions of photosynthesis occur that convert carbon dioxide into glucose. The stroma is the fluid-filled space inside the chloroplast, surrounding the thylakoid membranes where the light-dependent reactions take place. The Calvin cycle uses the energy from the light-dependent reactions to produce glucose, which is an essential process for plants to produce energy and store it in the form of carbohydrates.

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  • 5. 

    In any ecosystem, terrestrial or aquatic, what group(s) is (are) always necessary?

    • A.

      Photosynthesisers

    • B.

      Autotrophs and heterotrophs

    • C.

      Producers and primary consumers

    • D.

      Green plants

    • E.

      Autotrophs

    Correct Answer
    E. Autotrophs
    Explanation
    Autotrophs, also known as producers, are always necessary in any ecosystem, whether terrestrial or aquatic. They are organisms that can produce their own food through photosynthesis or chemosynthesis, converting energy from sunlight or inorganic chemicals into organic compounds. Autotrophs form the base of the food chain by providing energy and nutrients to other organisms. Without autotrophs, there would be no source of energy for the ecosystem, and it would collapse. Therefore, autotrophs are essential for the functioning and survival of any ecosystem.

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  • 6. 

    In autotrophic bacteria, where are the enzymes located that can carry on organic synthesis?

    • A.

      Free in the cytosol

    • B.

      Chloroplast membranes

    • C.

      Along the inner surface of the plasma membrane

    • D.

      Nuclear membranes

    • E.

      Along the outer edge of the nucleoid

    Correct Answer
    C. Along the inner surface of the plasma membrane
    Explanation
    In autotrophic bacteria, the enzymes that can carry on organic synthesis are located along the inner surface of the plasma membrane. This location allows for efficient utilization of resources and coordination of metabolic processes. The enzymes are positioned in close proximity to the cell membrane to facilitate the transport of substrates and products, ensuring a streamlined and efficient synthesis of organic compounds.

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  • 7. 

    When oxygen is released as a result of photosynthesis, it is a by-product of which of the following?

    • A.

      The electron transfer system of photosystem I

    • B.

      Splitting the water molecules

    • C.

      Reducing NADP+

    • D.

      Chemiosmosis

    • E.

      The electron transfer system of photosystem II

    Correct Answer
    B. Splitting the water molecules
    Explanation
    During the process of photosynthesis, water molecules are split in a process called photolysis. This occurs in the thylakoid membrane of chloroplasts, specifically in photosystem II. The splitting of water molecules releases oxygen as a by-product, which is then released into the atmosphere. This oxygen is essential for the survival of many organisms, including humans, as it is used in cellular respiration to produce energy. Therefore, the correct answer is splitting the water molecules.

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  • 8. 

    A plant has a unique photosynthetic pigment. The leaves of this plant appear to be reddish yellow. What wavelengths of visible light are being absorbed by this pigment?

    • A.

      Blue and violet

    • B.

      Green, blue, and yellow

    • C.

      Red and yellow

    • D.

      Blue, green, and red

    • E.

      Green and yellow

    Correct Answer
    A. Blue and violet
    Explanation
    The correct answer is blue and violet. This is because when the leaves appear reddish yellow, it means that the pigment is absorbing all other colors of visible light except for red, yellow, blue, and violet. Since red and yellow are not listed as options, it can be inferred that the pigment is absorbing blue and violet wavelengths of light.

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  • 9. 

     In the thylakoid membranes, what is the main role of the antenna pigment molecules?

    • A.

      Harvest photons and transfer light energy to the reaction-center chlorophyll

    • B.

      Concentrate photons within the stroma

    • C.

      Synthesis ATP from ADP and Pi

    • D.

      Transfer electrons and ferrodoxin and then NADPH

    • E.

      Split water and release oxygen to the reaction-center chorophyll

    Correct Answer
    A. Harvest photons and transfer light energy to the reaction-center chlorophyll
    Explanation
    The main role of the antenna pigment molecules in the thylakoid membranes is to harvest photons and transfer the light energy to the reaction-center chlorophyll. This allows for the efficient capture of light energy during photosynthesis, which is essential for the production of ATP and NADPH. The antenna pigment molecules act as light-absorbing pigments that capture photons and transfer the energy to the reaction-center chlorophyll, where the primary photochemical reactions occur.

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  • 10. 

    The reaction-center chlorophyll of photosystem I is known as P700 because

    • A.

      It absorbs 700 photons per microsecond.

    • B.

      There are 700 photosystem I components to each chloroplast.

    • C.

      This pigment is best at absorbing light with a wavelength of 700 nm.

    • D.

      There are 700 chlorophyll molecules in the center.

    • E.

      The plastoquinone reflects light with a wavelength of 700 nm.

    Correct Answer
    C. This pigment is best at absorbing light with a wavelength of 700 nm.
    Explanation
    The reaction-center chlorophyll of photosystem I is known as P700 because this pigment is best at absorbing light with a wavelength of 700 nm.

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  • 11. 

    Which of the events listed below occur in the light reactions of photosynthesis?

    • A.

      NADPH is reduced to NADP+.

    • B.

      NADP is produced.

    • C.

      Light is absorbed and funneled to reaction-center chlorophyll a.

    • D.

      Carbon dioxide is incorporated into PGA.

    • E.

      ATP is phosphorylated to yield ADP.

    Correct Answer
    C. Light is absorbed and funneled to reaction-center chlorophyll a.
    Explanation
    In the light reactions of photosynthesis, light is absorbed and funneled to reaction-center chlorophyll a. This process is essential for capturing energy from sunlight and converting it into chemical energy in the form of ATP and NADPH. The absorbed light energy is used to drive the electron transport chain, which ultimately leads to the production of ATP and the reduction of NADP+ to NADPH. This energy-rich molecules (ATP and NADPH) are then used in the subsequent dark reactions (Calvin cycle) to convert carbon dioxide into organic compounds.

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  • 12. 

    Which statement describes the functioning of photosystem II?

    • A.

      The electron vacancies in P680 are filled by electrons derived from water.

    • B.

      The excitation is passed along to a molecule of P700 chlorophyll in the photosynthetic unit.

    • C.

      Light energy excites electrons in the electron transport chain in a photosynthetic unit.

    • D.

      The splitting of water yields molecular carbon dioxide as a by-product.

    • E.

      The P680 chlorophyll donates a pair of protons to NADPH, which is thus converted to NADP+.

    Correct Answer
    A. The electron vacancies in P680 are filled by electrons derived from water.
    Explanation
    Photosystem II is the first protein complex in the light-dependent reactions of photosynthesis. It functions by absorbing light energy and using it to excite electrons in the chlorophyll molecules. These excited electrons are then passed along an electron transport chain, and the electron vacancies in P680, a chlorophyll molecule, are filled by electrons derived from water. This process is known as photolysis, and it results in the release of molecular oxygen as a by-product.

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  • 13. 

    Which of the following are directly associated with photosystem I?

    • A.

      Receiving electrons from plastocyanin

    • B.

      P680 reaction-center chlorophyll

    • C.

      Extraction of hydrogen electrons from the splitting of water

    • D.

      Harvesting of light energy by ATP

    • E.

      Passing electrons to plastoquinone

    Correct Answer
    A. Receiving electrons from plastocyanin
    Explanation
    Photosystem I is directly associated with receiving electrons from plastocyanin. Plastocyanin is a copper-containing protein that functions as an electron carrier in the electron transport chain of photosynthesis. It transfers electrons from the cytochrome b6f complex to photosystem I, where they are used to reduce NADP+ to NADPH. This is an essential step in the light-dependent reactions of photosynthesis, which ultimately produce ATP and NADPH for the Calvin cycle.

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  • 14. 

    Some photosynthetic organisms contain chloroplasts that lack photosystem II, yet are able to survive. The best way to detect the lack of photosystem II in these organisms would be

    • A.

      To do experiments to generate an action spectrum.

    • B.

      To test for liberation of O2 in the light.

    • C.

      To test for CO2 fixation in the dark.

    • D.

      To test for production of either sucrose or starch.

    • E.

      To determine if they have thylakoids in the chloroplasts.

    Correct Answer
    B. To test for liberation of O2 in the light.
    Explanation
    The best way to detect the lack of photosystem II in these organisms would be to test for liberation of O2 in the light. Photosystem II is responsible for the splitting of water molecules and the release of oxygen as a byproduct during photosynthesis. If an organism lacks photosystem II, it would not be able to produce oxygen in the presence of light. Therefore, testing for the liberation of O2 in the light would be a reliable method to determine the absence of photosystem II in these organisms.

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  • 15. 

    What are the products of linear photophosphorylation?

    • A.

      P700 and P680

    • B.

      Heat and fluorescence

    • C.

      ATP and NADPH

    • D.

      ATP and P700

    • E.

      ADP and NADP

    Correct Answer
    C. ATP and NADPH
    Explanation
    Linear photophosphorylation is the process in photosynthesis where light energy is used to generate ATP and NADPH. During this process, the energy from photons is absorbed by chlorophyll molecules, specifically P700 and P680, which are located in the photosystem I and photosystem II respectively. This energy is then used to drive the synthesis of ATP and the reduction of NADP+ to NADPH, which are essential for the production of glucose and other organic molecules in the Calvin cycle. Therefore, the correct answer is ATP and NADPH.

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  • 16. 

    As a research scientist, you measure the amount of ATP and NADPH consumed by the Calvin cycle in 1 hour. You find 30,000 molecules of ATP consumed, but only 20,000 molecules of NADPH. Where did the extra ATP molecules come from?

    • A.

      Chlorophyll

    • B.

      Photosystem II

    • C.

      Linear electron flow

    • D.

      Cyclic electron flow

    • E.

      Photosystem I

    Correct Answer
    D. Cyclic electron flow
    Explanation
    Cyclic electron flow is the process in photosynthesis where electrons are recycled back to the photosystem I instead of being transferred to NADP+ to produce NADPH. This process generates ATP using the electron transport chain. In this case, the extra ATP molecules came from cyclic electron flow, which produced additional ATP without consuming NADPH.

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  • 17. 

    Assume a thylakoid is somehow punctured so that the interior of the thylakoid is no longer separated from the stroma. This damage will have the most direct effect on which of the following processes?

    • A.

      The splitting of water

    • B.

      The flow of electrons from photosystem II to photosystem I

    • C.

      The reduction of NADP+

    • D.

      The absorption of light energy by chlorophyll

    • E.

      The synthesis of ATP

    Correct Answer
    E. The synthesis of ATP
    Explanation
    The synthesis of ATP occurs in the thylakoid membrane during the light-dependent reactions of photosynthesis. If the thylakoid is punctured and the interior is no longer separated from the stroma, it will disrupt the formation of a proton gradient across the thylakoid membrane, which is necessary for ATP synthesis. Therefore, the damage to the thylakoid will have the most direct effect on the synthesis of ATP.

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  • 18. 

    What does the chemiosmotic process in chloroplasts involve?

    • A.

      Establishment of a proton gradient

    • B.

      Reduction of water to produce ATP energy

    • C.

      Diffusion of electrons through the thylakoid membrane

    • D.

      Movement of water by osmosis into the thylakoid space from the stroma

    • E.

      Formation of glucose, using carbon dioxide, NADPH, and ATP

    Correct Answer
    A. Establishment of a proton gradient
    Explanation
    The chemiosmotic process in chloroplasts involves the establishment of a proton gradient. This means that during photosynthesis, protons (H+) are pumped across the thylakoid membrane, creating a concentration gradient. This gradient is then used by ATP synthase to produce ATP, which is the energy currency of the cell. The movement of protons down their concentration gradient drives the synthesis of ATP, making the establishment of a proton gradient a crucial step in the chemiosmotic process.

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  • 19. 

    Suppose the interior of the thylakoids of isolated chloroplasts were made acidic and then transferred in the dark to a pH-8 solution. What would be likely to happen?

    • A.

      The isolated chloroplasts will make ATP.

    • B.

      Cyclic photophosphorylation will occur.

    • C.

      The Calvin cycle will be activated.

    • D.

      Only A and B will occur.

    • E.

      A, B and C will occur.

    Correct Answer
    A. The isolated chloroplasts will make ATP.
    Explanation
    When the interior of the thylakoids of isolated chloroplasts is made acidic and then transferred to a pH-8 solution, the proton gradient across the thylakoid membrane will be disrupted. This disruption will prevent the generation of ATP through noncyclic photophosphorylation, which requires a proton gradient. However, cyclic photophosphorylation can still occur, as it does not rely on a proton gradient. The Calvin cycle, which is responsible for carbon fixation, does not directly depend on the pH of the solution, so it may or may not be activated. Therefore, the most likely outcome is that only ATP production through cyclic photophosphorylation and noncyclic photophosphorylation will occur.

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  • 20. 

    In a plant cell, where are the ATP synthase complexes located?

    • A.

      Inner mitochondrial membrane

    • B.

      Plasma membrane

    • C.

      Thylakoid membrane

    • D.

      A and C

    • E.

      A, B and C

    Correct Answer
    D. A and C
    Explanation
    ATP synthase complexes are located in the inner mitochondrial membrane and the thylakoid membrane. This is because ATP synthesis occurs in both the mitochondria and chloroplasts of plant cells. The inner mitochondrial membrane is responsible for oxidative phosphorylation, where ATP is produced through the electron transport chain. The thylakoid membrane is found in the chloroplasts and is involved in photosynthesis, where ATP is generated through the light-dependent reactions. Therefore, the correct answer is A and C.

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  • 21. 

    In mitochondria, chemiosmosis translocates protons from the matrix into the intermembrane space, whereas in chloroplasts, chemiosmosis translocates protons from

    • A.

      The intermembrane space to the matrix.

    • B.

      The stroma to the thylakoid space.

    • C.

      The stroma to the photosystem II.

    • D.

      The matrix to the stroma.

    • E.

      ATP synthase to NADP+ reductase.

    Correct Answer
    B. The stroma to the thylakoid space.
    Explanation
    In chloroplasts, chemiosmosis translocates protons from the stroma to the thylakoid space. This movement of protons creates an electrochemical gradient, which is then used by ATP synthase to produce ATP. The thylakoid space is the site where the light-dependent reactions of photosynthesis occur, and the movement of protons from the stroma to the thylakoid space is essential for the generation of ATP during photosynthesis.

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  • 22. 

    Which of the following statements best describes the relationship between photosynthesis and respiration?

    • A.

      Photosynthesis stores energy in complex organic molecules, while respiration releases it.

    • B.

      Respiration is anabolic and photosynthesis is catabolic.

    • C.

      Respiration is the reversal of the biochemical pathways of photosynthesis.

    • D.

      ATP molecules are produced in photosynthesis and used up in respiration.

    • E.

      Photosynthesis occurs only in plants and respiration occurs only in animals.

    Correct Answer
    A. Photosynthesis stores energy in complex organic molecules, while respiration releases it.
    Explanation
    Photosynthesis is the process by which plants convert sunlight into chemical energy and store it in the form of complex organic molecules such as glucose. On the other hand, respiration is the process by which cells break down these complex organic molecules and release the stored energy in the form of ATP. Therefore, the statement "Photosynthesis stores energy in complex organic molecules, while respiration releases it" accurately describes the relationship between photosynthesis and respiration.

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  • 23. 

    Where are the molecules of the electron transport chain found in plant cells?

    • A.

      Inner membrane of mitochondria

    • B.

      Stroma of chloroplast

    • C.

      Matrix of mitochondria

    • D.

      Thylakoid membranes of chloroplasts

    • E.

      Cytoplasm

    Correct Answer
    D. Thylakoid membranes of chloroplasts
    Explanation
    The molecules of the electron transport chain are found in the thylakoid membranes of chloroplasts. This is where the process of photosynthesis takes place in plant cells. The electron transport chain is responsible for transferring electrons and generating energy in the form of ATP. The thylakoid membranes contain the necessary proteins and pigments, such as chlorophyll, that are involved in capturing light energy and driving the electron transport chain.

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  • 24. 

    Synthesis of ATP by the chemiosmotic mechanism occurs during

    • A.

      Both photosynthesis and respiration.

    • B.

      Respiration.

    • C.

      Photorespiration.

    • D.

      Neither photosynthesis nor respiration.

    • E.

      Photosynthesis.

    Correct Answer
    A. Both photosynthesis and respiration.
    Explanation
    The chemiosmotic mechanism is responsible for the synthesis of ATP in both photosynthesis and respiration. In photosynthesis, ATP is synthesized during the light-dependent reactions in the thylakoid membrane of chloroplasts. In respiration, ATP is synthesized during oxidative phosphorylation in the inner mitochondrial membrane. This mechanism involves the generation of a proton gradient across the membrane, which is then used by ATP synthase to produce ATP. Therefore, both photosynthesis and respiration utilize the chemiosmotic mechanism to synthesize ATP.

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  • 25. 

    Reduction of oxygen which forms water occurs during

    • A.

      Photosynthesis

    • B.

      Both photosynthesis and respiration.

    • C.

      Neither photosynthesis nor respiration.

    • D.

      Respiration.

    • E.

      Photorespiration.

    Correct Answer
    D. Respiration.
    Explanation
    The reduction of oxygen which forms water occurs during respiration. During respiration, glucose is broken down in the presence of oxygen to produce energy, carbon dioxide, and water. Oxygen is reduced during this process to form water. In photosynthesis, on the other hand, oxygen is produced as a byproduct when water is split during the light-dependent reactions. Therefore, the correct answer is respiration.

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  • 26. 

    Reduction of NADP+ occurs during

    • A.

      Neither photosynthesis nor respiration.

    • B.

      Respiration.

    • C.

      Photorespiration.

    • D.

      Photosynthesis.

    • E.

      Both photosynthesis and respiration.

    Correct Answer
    D. Photosynthesis.
    Explanation
    During photosynthesis, reduction of NADP+ occurs. NADP+ (nicotinamide adenine dinucleotide phosphate) is a coenzyme that plays a crucial role in the electron transfer chain of photosynthesis. It accepts electrons and protons from water molecules, forming NADPH, which is an energy-rich molecule used in the synthesis of glucose. In contrast, during respiration, NAD+ (nicotinamide adenine dinucleotide) is reduced to NADH, not NADP+. Therefore, the reduction of NADP+ only occurs during photosynthesis, making "photosynthesis" the correct answer.

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  • 27. 

    The splitting of carbon dioxide to form oxygen gas and carbon compounds occurs during

    • A.

      Respiration.

    • B.

      Photorespiration.

    • C.

      Neither photosynthesis nor respiration.

    • D.

      Both photosynthesis and respiration.

    • E.

      Photosynthesis

    Correct Answer
    C. Neither photosynthesis nor respiration.
    Explanation
    The splitting of carbon dioxide to form oxygen gas and carbon compounds occurs during neither photosynthesis nor respiration. This is because during photosynthesis, carbon dioxide is converted into glucose and oxygen is released as a byproduct. In respiration, glucose is broken down to release energy, and carbon dioxide is produced as a waste product. Therefore, neither process involves the splitting of carbon dioxide to form oxygen gas and carbon compounds.

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  • 28. 

    Generation of proton gradients across membranes occurs during

    • A.

      Neither photosynthesis nor respiration.

    • B.

      Respiration.

    • C.

      Both photosynthesis and respiration.

    • D.

      Photosynthesis.

    • E.

      Photorespiration.

    Correct Answer
    C. Both photosynthesis and respiration.
    Explanation
    During both photosynthesis and respiration, proton gradients are generated across membranes. In photosynthesis, proton gradients are formed during the light reactions, where light energy is used to split water molecules and generate ATP and NADPH. In respiration, proton gradients are formed during the electron transport chain, where electrons are transferred through a series of protein complexes, generating ATP through chemiosmosis. Therefore, both photosynthesis and respiration involve the generation of proton gradients across membranes.

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  • 29. 

    What is the relationship between wavelength of light and the quantity of energy per photon?

    • A.

      They are logarithmically related.

    • B.

      They are separate phenomena.

    • C.

      They are only related in certain parts of the spectrum

    • D.

      They have a direct, linear relationship.

    • E.

      They are inversely related.

    Correct Answer
    E. They are inversely related.
    Explanation
    The relationship between wavelength of light and the quantity of energy per photon is that they are inversely related. This means that as the wavelength of light increases, the quantity of energy per photon decreases, and vice versa.

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  • 30. 

    In a protein complex for the light reaction (a reaction center), energy is transferred from pigment molecule to pigment molecule, to a special chlorophyll a molecule, and eventually to the primary electron acceptor. Why does this occur?

    • A.

      The potential energy of the electron has to go back to the ground state.

    • B.

      The action spectrum of that molecule is such that it is different from other molecules of chlorophyll.

    • C.

      The molecular environment lets it boost an electron to a higher energy level and also to transfer the electron to another molecule.

    • D.

      These chlorophyll a molecules are associated with higher concentrations of ATP.

    • E.

      Each pigment molecule has to be able to act independently to excite electrons.

    Correct Answer
    C. The molecular environment lets it boost an electron to a higher energy level and also to transfer the electron to another molecule.
    Explanation
    The given answer states that the molecular environment allows for the boosting of an electron to a higher energy level and facilitates the transfer of the electron to another molecule. This suggests that the arrangement and properties of the molecules in the protein complex enable the efficient transfer of energy from pigment molecule to pigment molecule, ultimately leading to the transfer of the electron to the primary electron acceptor. This explanation aligns with the process of energy transfer in the light reaction of photosynthesis.

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  • 31. 

    P680+ is said to be the strongest biological oxidising agent. Why?

    • A.

      This molecule is found far more frequently among bacteria as well as in plants and plantlike Protists.

    • B.

      It is the receptor for the most excited electron in either photosystem.

    • C.

      This molecule results from the transfer of an electron to the primary electron acceptor of photosystem II and strongly attracts another electron.

    • D.

      It is the molecule that transfers electrons to plastoquinone (Pq) of the electron transfer system.

    • E.

      NADP reductase will then catalyse the shift of the electron from Fd to NADP+ to reduce it to NADPH.

    Correct Answer
    C. This molecule results from the transfer of an electron to the primary electron acceptor of photosystem II and strongly attracts another electron.
    Explanation
    P680+ is considered the strongest biological oxidizing agent because it is formed when an electron is transferred to the primary electron acceptor of photosystem II. This molecule has a strong attraction for another electron, making it highly effective at oxidizing other molecules. It is found frequently in bacteria, plants, and plantlike Protists, and it plays a crucial role in the electron transfer system by transferring electrons to plastoquinone (Pq). This ultimately leads to the reduction of NADP+ to NADPH through the catalysis of NADP reductase.

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  • 32. 

    Some photosynthetic bacteria (e.g., purple sulfur bacteria) have photosystem I but not II, while others (e.g. cyanobacteria) have both PSI and PSII. Which of the following might this observation imply?

    • A.

      Photosystem II may have evolved to be more photoprotective.

    • B.

      Cyclic flow must be the most necessary of the two processes.

    • C.

      Cyclic flow must be more primitive than linear flow of electrons.

    • D.

      Photosystem II must have been selected against in some species.

    • E.

      Photosystem I must be more ancestral.

    Correct Answer
    E. Photosystem I must be more ancestral.
    Explanation
    This observation suggests that photosystem I (PSI) is more ancestral than photosystem II (PSII) in bacteria. This means that PSI likely evolved before PSII. The presence of PSI in some bacteria and the presence of both PSI and PSII in others indicates that PSI is a more fundamental and ancient form of photosynthesis, while PSII may have evolved later as an adaptation for more efficient light capture and photoprotection.

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  • 33. 

    Cyclic electron flow may be photoprotective (protective to light-induced damage). Which of the following experiments could provide information on this phenomenon?

    • A.

      Using mutated organisms that can grow but that cannot carry out cyclic flow of electrons and compare their abilities to photosynthesise in different light intensities

    • B.

      Using bacteria with only cyclic flow and measuring the number and types of photosynthetic pigments they have in their membranes

    • C.

      Using plants with only photosystem I operative and measure how much damage occurs at different wavelengths.

    • D.

      Using plants that can carry out both linear and cyclic electron flow, or only one or another of the processes, and measuring their light absorbance

    • E.

      Using plants that can carry out both linear and cyclic electron flow, or only one or another of thee processes, and measuring their light absorbance

    Correct Answer
    A. Using mutated organisms that can grow but that cannot carry out cyclic flow of electrons and compare their abilities to photosynthesise in different light intensities
    Explanation
    This experiment would provide information on the photoprotective nature of cyclic electron flow. By comparing the abilities of mutated organisms that cannot carry out cyclic flow of electrons to photosynthesize in different light intensities, we can determine if cyclic flow plays a role in protecting against light-induced damage. If the mutated organisms have reduced abilities to photosynthesize in high light intensities compared to normal organisms, it suggests that cyclic flow is indeed photoprotective.

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  • 34. 

    Carotenoids are often found in foods that are considered to have antioxidant properties in human nutrition. What related function do they have in plants?

    • A.

      They serve as accessory pigments.

    • B.

      They dissipate excessive light energy.

    • C.

      They cover the sensitive chromosomes of the plant.

    • D.

      They take up toxins from the water.

    • E.

      They reflect orange light.

    Correct Answer
    B. They dissipate excessive light energy.
    Explanation
    Carotenoids serve as accessory pigments in plants, meaning they work alongside chlorophyll to capture light energy for photosynthesis. However, their main function is to dissipate excessive light energy. This is important because high levels of light energy can cause damage to plant cells and lead to the production of harmful reactive oxygen species. Carotenoids help protect the plant by absorbing and safely dissipating this excess energy, preventing potential harm.

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  • 35. 

    In thylakoids, protons travel through ATP synthase from the stroma to the thylakoid space. Therefore the catalytic "knobs" of ATP synthase would be located

    • A.

      On the stroma side of the membrane.

    • B.

      On the pigment molecules of PSI and PSII.

    • C.

      On the side facing the thylakoid space.

    • D.

      Built into the center of the thylkoid stack (granum).

    • E.

      On the ATP molecules themselves.

    Correct Answer
    A. On the stroma side of the membrane.
    Explanation
    The correct answer is "on the stroma side of the membrane" because ATP synthase is responsible for generating ATP using the energy from the flow of protons from the thylakoid space to the stroma. This flow of protons occurs through ATP synthase, and the catalytic "knobs" of ATP synthase are located on the stroma side of the membrane where they can interact with ADP and inorganic phosphate to synthesize ATP.

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  • 36. 

    Which of the following statements best represents the relationships between the light reactions and the Calvin cycle?

    • A.

      The light reactions provide ATP and NADPH to the Calvin cycle, and the cycle returns ADP, Pi, and NADP+ to the light reactions.

    • B.

      The light reactions provide the Calvin cycle with oxygen for electron flow, and the Calvin cycle provides the light reactions with water to split.

    • C.

      The light reactions provide the Calvin cycle with oxygen for electron flow, and the Calvin cycle provides the light reactions with water to split.

    • D.

      The light reactions provide ATP and NADPH to the carbon fixation step of the Calvin cycle, and the cycle provides water and electrons to the light reactions.

    • E.

      There is no relationship between the light reactions and the Calvin cycle.

    Correct Answer
    A. The light reactions provide ATP and NADPH to the Calvin cycle, and the cycle returns ADP, Pi, and NADP+ to the light reactions.
    Explanation
    The light reactions in photosynthesis produce ATP and NADPH, which are then used by the Calvin cycle to convert carbon dioxide into glucose. In return, the Calvin cycle provides the light reactions with ADP, Pi (inorganic phosphate), and NADP+ to be used again in the production of ATP and NADPH. This reciprocal exchange of energy and molecules between the light reactions and the Calvin cycle allows for the continuous flow of energy and the synthesis of glucose in photosynthesis.

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  • 37. 

    Where do the enzymatic reactions of the Calvin cycle take place?

    • A.

      Thylakoid space

    • B.

      Stroma of the chloroplast

    • C.

      Thylakoid membranes

    • D.

      Electron transport chain

    • E.

      Outer membrane of the chloroplast

    Correct Answer
    B. Stroma of the chloroplast
    Explanation
    The enzymatic reactions of the Calvin cycle take place in the stroma of the chloroplast. The stroma is the fluid-filled region of the chloroplast that surrounds the thylakoid membranes. It contains the enzymes necessary for the Calvin cycle, which is the process by which plants convert carbon dioxide into glucose during photosynthesis. The thylakoid space and thylakoid membranes are involved in the light-dependent reactions of photosynthesis, while the electron transport chain is part of the process that generates ATP. The outer membrane of the chloroplast does not directly participate in the Calvin cycle.

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  • 38. 

    What is the primary function of the Calvin cycle? 

    • A.

      Transport RuBP out of the chloroplast

    • B.

      Split water and release oxygen

    • C.

      Use NADPH to release carbon dioxide

    • D.

      Synthesise simple sugars from carbon dioxide

    • E.

      Use ATP to release carbon dioxide

    Correct Answer
    D. Synthesise simple sugars from carbon dioxide
    Explanation
    The primary function of the Calvin cycle is to synthesize simple sugars from carbon dioxide. This process occurs in the chloroplasts of plants during photosynthesis. The Calvin cycle uses energy from ATP and NADPH, which are produced in the light-dependent reactions, to convert carbon dioxide into glucose and other sugars. This process is essential for plants to produce food and store energy.

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  • 39. 

    Produces molecular oxygen (O2)

    • A.

      Light reactions alone

    • B.

      The Calvin cycle alone

    • C.

      Both the light reactions and the Calvin cycle

    • D.

      Neither the light reactions nor the Calvin cycle

    • E.

      Occurs in the chloroplast but is not part of photosynthesis

    Correct Answer
    A. Light reactions alone
    Explanation
    The correct answer is "light reactions alone". The light reactions of photosynthesis are responsible for producing molecular oxygen (O2). These reactions occur in the thylakoid membranes of the chloroplasts and involve the absorption of light energy to generate ATP and NADPH, which are then used in the Calvin cycle to convert carbon dioxide into glucose. Therefore, the light reactions alone are responsible for the production of molecular oxygen, while the Calvin cycle is responsible for the synthesis of glucose.

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  • 40. 

    Requires ATP 

    • A.

      Light reactions alone

    • B.

      The Calvin cycle alone

    • C.

      Both the light reactions and the Calvin cycle

    • D.

      Neither the light reactions nor the Calvin cycle

    • E.

      Occurs in the chloroplast but is not part of photosynthesis

    Correct Answer
    B. The Calvin cycle alone
    Explanation
    The Calvin cycle is the process in photosynthesis that occurs in the stroma of the chloroplasts and is responsible for converting carbon dioxide into glucose. It does not require ATP directly, but it does rely on the products of the light reactions (ATP and NADPH) to provide the energy and reducing power needed for the cycle to occur. Therefore, the Calvin cycle alone requires ATP indirectly through the light reactions.

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  • 41. 

    Produces NADH

    • A.

      Light reactions alone

    • B.

      The Calvin cycle alone

    • C.

      Both the light reactions and the Calvin cycle

    • D.

      Neither the light reactions nor the Calvin cycle

    • E.

      Occurs in the chloroplast but is not part of photosynthesis

    Correct Answer
    D. Neither the light reactions nor the Calvin cycle
    Explanation
    The statement "neither the light reactions nor the Calvin cycle" means that the process of producing NADH does not occur in either the light reactions or the Calvin cycle. This suggests that another process or pathway is responsible for producing NADH.

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  • 42. 

    Produces NADPH

    • A.

      Light reactions alone

    • B.

      The Calvin cycle alone

    • C.

      Both the light reactions and the Calvin cycle

    • D.

      Neither the light reactions nor the Calvin cycle

    • E.

      Occurs in the chloroplast but is not part of photosynthesis

    Correct Answer
    A. Light reactions alone
    Explanation
    The light reactions in photosynthesis are responsible for producing NADPH. NADPH is an important molecule in the process of photosynthesis as it acts as a reducing agent, providing electrons to drive the synthesis of glucose during the Calvin cycle. Therefore, the correct answer is that NADPH is produced by the light reactions alone.

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  • 43. 

    Produces three-carbon sugars

    • A.

      Light reactions alone

    • B.

      The Calvin cycle alone

    • C.

      Both the light reactions and the Calvin cycle

    • D.

      Neither the light reactions nor the Calvin cycle

    • E.

      Occurs in the chloroplast but is not part of photosynthesis

    Correct Answer
    B. The Calvin cycle alone
    Explanation
    The Calvin cycle alone produces three-carbon sugars. The Calvin cycle is a series of biochemical reactions that occur in the chloroplasts of plants during photosynthesis. It uses energy from ATP and NADPH, which are produced in the light reactions, to convert carbon dioxide into glucose and other organic compounds. Therefore, the Calvin cycle is responsible for the synthesis of sugars, while the light reactions provide the energy needed for this process.

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  • 44. 

    Requires CO2

    • A.

      Light reactions alone

    • B.

      The Calvin cycle alone

    • C.

      Both the light reactions and the Calvin cycle

    • D.

      Neither the light reactions nor the Calvin cycle

    • E.

      Occurs in the chloroplast but is not part of photosynthesis

    Correct Answer
    B. The Calvin cycle alone
    Explanation
    The Calvin cycle alone requires CO2. The Calvin cycle is a series of chemical reactions that occur in the chloroplasts of plants and some bacteria. It is part of the process of photosynthesis and is responsible for converting carbon dioxide into glucose, a form of stored energy. The Calvin cycle does not directly require light, unlike the light reactions which do require light energy to produce ATP and NADPH. Therefore, the correct answer is that the Calvin cycle alone requires CO2.

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  • 45. 

    Requires glucose

    • A.

      Light reactions alone

    • B.

      The Calvin cycle alone

    • C.

      Both the light reactions and the Calvin cycle

    • D.

      Neither the light reactions nor the Calvin cycle

    • E.

      Occurs in the chloroplast but is not part of photosynthesis

    Correct Answer
    D. Neither the light reactions nor the Calvin cycle
    Explanation
    This answer suggests that the process in question does not require either the light reactions or the Calvin cycle. This means that it is not directly involved in photosynthesis, as both the light reactions and the Calvin cycle are essential components of photosynthesis.

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  • 46. 

    The sugar that results from three "turns" of the Calvin cycle is glyceraldehyde-3-phosphate (G3P). Which of the following is a consequence of this?

    • A.

      G3P is easier for a plant to store.

    • B.

      Formation of a molecule of glucose would require 9 "turns."

    • C.

      Some plants would not taste sweet to us.

    • D.

      G3P more readily forms sucrose and other disaccharides than it does monosaccharides.

    • E.

      The formation of starch in plants involves assembling many G3P molecules, with or without further rearrangements.

    Correct Answer
    E. The formation of starch in plants involves assembling many G3P molecules, with or without further rearrangements.
    Explanation
    The formation of starch in plants involves assembling many G3P molecules, with or without further rearrangements. This means that G3P is used as a building block for starch formation, and multiple G3P molecules are combined to form starch. This is a consequence of G3P being the sugar that results from three "turns" of the Calvin cycle.

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  • 47. 

    In an experiment studying photosynthesis performed during the day, you provide a plant with radioactive carbon (14C) dioxide as a metabolic tracer. The 14C is incorporated first into oxaloacetate. The plant is best characterised as a

    • A.

      Chemoautotroph.

    • B.

      C4 plant.

    • C.

      CAM plant.

    • D.

      Heterotroph

    • E.

      C3 plant.

    Correct Answer
    B. C4 plant.
    Explanation
    In this experiment, the plant is provided with radioactive carbon dioxide (14C) as a metabolic tracer. The 14C is incorporated first into oxaloacetate. This characteristic is specific to C4 plants, which have a unique carbon fixation pathway called the C4 pathway. In C4 plants, oxaloacetate is the first stable compound formed during carbon fixation. Therefore, the plant in this experiment can be best characterized as a C4 plant.

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  • 48. 

    Why are C4 plants able to photosynthesise with no apparent photorespiration?

    • A.

      They conserve water more efficiently.

    • B.

      They do not participate in the Calvin cycle.

    • C.

      They exclude oxygen from their tissues.

    • D.

      They use PEP carboxylase to initially fix CO2.

    • E.

      They are adapted to cold, wet climates.

    Correct Answer
    D. They use PEP carboxylase to initially fix CO2.
    Explanation
    C4 plants are able to photosynthesize with no apparent photorespiration because they use PEP carboxylase to initially fix CO2. This enzyme has a higher affinity for CO2 than oxygen, preventing the oxygenase activity that leads to photorespiration. By using PEP carboxylase, C4 plants are able to efficiently fix CO2 and avoid the wasteful process of photorespiration, allowing them to conserve energy and resources.

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  • 49. 

    CAM plants keep stomata closed in daytime, thus reducing loss of water. They can do this because they

    • A.

      Fix CO2 into pyruvate in the mesophyll cells.

    • B.

      Fix CO2 into organic acids during the night.

    • C.

      Use photosystems I and II at night.

    • D.

      Use the enzyme phosphofructokinase, which outcompetes rubisco for CO2.

    • E.

      Fix CO2 into sugars in the bundle-sheath cells.

    Correct Answer
    B. Fix CO2 into organic acids during the night.
    Explanation
    CAM plants keep stomata closed in daytime to reduce water loss. They fix CO2 into organic acids during the night as a way to store carbon dioxide. This allows them to perform photosynthesis during the day using the stored CO2 without needing to open their stomata and risk losing water. By fixing CO2 into organic acids, CAM plants can efficiently utilize carbon dioxide while minimizing water loss.

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  • 50. 

    Photorespiration lowers the efficiency of photosynthesis by preventing the formation of

    • A.

      ATP molecules.

    • B.

      Ribulose bisphosphate molecules.

    • C.

      3-phosphoglycerate molecules

    • D.

      Carbon dioxide molecules.

    • E.

      RuBP carboxylase molecules.

    Correct Answer
    C. 3-phosphoglycerate molecules
    Explanation
    Photorespiration is a metabolic process that occurs in plants when there is a high concentration of oxygen and low concentration of carbon dioxide. It leads to the breakdown of 3-phosphoglycerate molecules, which are important intermediates in the Calvin cycle of photosynthesis. This breakdown results in the loss of carbon dioxide and energy, reducing the efficiency of photosynthesis. Therefore, the presence of photorespiration prevents the formation of 3-phosphoglycerate molecules, leading to a decrease in the efficiency of photosynthesis.

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  • Apr 09, 2024
    Quiz Edited by
    ProProfs Editorial Team
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