Question 1

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?

Accepted Answer

Cyclic electron flow produces ATP but not NADPH. This could account for the extra ATP molecules consumed by the Calvin cycle. Photosystem II and photosystem I are involved in linear electron flow, which produces both ATP and NADPH. Chlorophyll is a pigment involved in light absorption, but it does not directly produce ATP or NADPH.

Question 2

Which of the following are directly associated with photosystem I?

Accepted Answer

Photosystem I receives electrons from the thylakoid membrane electron transport chain, making option B the correct answer. Harvesting of light energy by ATP is associated with photosystem II, extraction of hydrogen electrons from the splitting of water produces oxygen and is associated with photosystem II, and passing electrons to the thylakoid membrane electron transport chain is also associated with photosystem II.

Question 3

What does the chemiosmotic process in chloroplasts involve?

Accepted Answer

The chemiosmotic process in chloroplasts involves the establishment of a proton gradient across the thylakoid membrane. This gradient is created by the movement of protons across the membrane, which drives the synthesis of ATP.

Question 4

In autotrophic bacteria,where are the enzymes located that can carry on carbon fixation (reduction of carbon dioxide to carbohydrate)?

Accepted Answer

The answer of In autotrophic bacteria,where are the enzymes located...

Question 5

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?

Accepted Answer

The synthesis of ATP occurs in the thylakoid membrane using the energy from the flow of electrons and the proton gradient across the membrane. If the thylakoid is punctured and the interior is no longer separated from the stroma, the proton gradient will dissipate and the synthesis of ATP will be disrupted.

Question 6

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

Accepted Answer

The products of the light reactions that are utilized in the Calvin cycle are ATP and NADPH. These two molecules provide the energy and reducing power needed for carbon fixation in the Calvin cycle.

Question 7

Which statement describes the functioning of photosystem II?

Accepted Answer

Photosystem II functions by using light energy to excite electrons in the P680 chlorophyll. These excited electrons are passed along a thylakoid membrane electron transport chain, and the electron vacancies in P680⁺ are filled by electrons derived from the splitting of water. This process results in the release of oxygen as a by-product. Therefore, the best choice is D, which describes the splitting of water to fill the electron vacancies in P680⁺.

Question 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?

Accepted Answer

The color of the leaves is determined by the wavelengths of light that are reflected, not absorbed. Since the leaves appear reddish yellow, it means that red and yellow wavelengths are being reflected, while the complementary colors, such as blue and violet, are being absorbed by the pigment.

Question 9

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

Accepted Answer

ATP synthase complexes are located on both the thylakoid membrane within chloroplasts and the inner mitochondrial membrane within mitochondria.

Question 10

If photosynthesizing green algae are provided with CO₂ synthesized 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

Accepted Answer

During photosynthesis, the oxygen atoms in the CO₂ molecules do not end up in the O₂ produced. Instead, the O₂ released comes from the splitting of water (H₂O) molecules in the light-dependent reactions, not from the carbon dioxide (CO₂) used in the Calvin cycle. Therefore, if CO₂ with ¹⁸O is used, the ¹⁸O would be incorporated into the carbon fixation products (3-phosphoglycerate, glyceraldehyde 3-phosphate (G3P), glucose, and ribulose bisphosphate (RuBP)) but not in the molecular oxygen (O₂) released.

Question 11

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?

Accepted Answer

The acidification of the thylakoid interior, followed by placement in a basic solution, creates a proton gradient across the thylakoid membrane. This gradient drives ATP synthesis through chemiosmosis, similar to the process occurring during the light reactions of photosynthesis, but without the need for light in this experimental setup.

Question 12

Which of the following best describes decomposers?

Accepted Answer

Decomposers are heterotrophs that obtain their nutrition from dead organic matter, such as leaves, and break it down into simpler forms that can be reused by other organisms in the ecosystem. They play a vital role in the nutrient cycle of an ecosystem, as they release essential nutrients back into the soil for plants and other organisms to use.

Question 13

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

Accepted Answer

The absence of photosystem II means that these organisms cannot perform oxygenic photosynthesis and do not produce oxygen as a byproduct. Therefore, testing for liberation of O₂ in the light is the best way to detect the lack of photosystem II in these organisms.

Question 14

What are the products of linear photophosphorylation?

Accepted Answer

Linear photophosphorylation involves the conversion of light energy into the chemical energy of ATP and NADPH. Heat and fluorescence are not products of this process, and P700 and P680 are the names of the reaction center chlorophyll molecules in photosystem I and II, respectively, but they are not products of linear photophosphorylation. ATP and P700 are also not correct choices as P700 is a part of photosystem I and not involved in linear photophosphorylation. The correct products of this process are ATP and NADPH, making choice C the best answer. ADP and NADP are the reactants for linear photophosphorylation, not the products.

Question 15

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

Accepted Answer

The main role of the antenna pigment molecules, such as chlorophylls and carotenoids, is to harvest photons and transfer the light energy to the reaction-center chlorophyll. This transfer of energy allows for the initiation of the light-dependent reactions of photosynthesis, leading to the production of ATP and NADPH, which are used in the Calvin cycle to produce glucose.

Question 16

When oxygen is released as a result of photosynthesis,it is a direct by-product of

Accepted Answer

Oxygen is released as a by-product of photosynthesis when water molecules are split during the light-dependent reactions in photosystem II.

Question 17

Where does the Calvin cycle take place?

Accepted Answer

The Calvin cycle takes place in the stroma of the chloroplast. This is where the enzymes and other molecules necessary for the cycle are located. The thylakoid membrane is where the light-dependent reactions of photosynthesis occur, but the Calvin cycle is a light-independent process that takes place in the stroma. The cytoplasm and interior of the thylakoid are not involved in the Calvin cycle, and the outer membrane of the chloroplast only serves as a boundary.

Question 18

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

Accepted Answer

Autotrophs, also known as producers, are always necessary in any ecosystem as they are the foundation of the food chain/web and convert energy from the sun into organic compounds that can be used by other organisms. Without autotrophs, there would be no energy input into the ecosystem and it would collapse. While heterotrophs and consumers are also important for the food chain, they can only exist if autotrophs are present to provide energy. Likewise, while photosynthesizers and green plants are types of autotrophs, not all autotrophs are photosynthetic or green.

Question 19

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

Accepted Answer

The event that occurs in the light reactions of photosynthesis is the absorption of light and funneling to reaction-centre chlorophyll a. This occurs in the thylakoid membrane of chloroplasts, where pigments such as chlorophyll and accessory pigments absorb light energy and transfer it to reaction-centre chlorophyll a. This event starts the process of photosynthesis and generates ATP and NADPH, which are used in the subsequent dark reactions to convert CO2 into glucose.

Question 20

Halobacterium has a photosynthetic membrane that is coloured purple.Its photosynthetic action spectrum is exactly complementary (opposite to)the action spectrum for green plants.What wavelengths of light do the Halobacterium photosynthetic pigments absorb?

Accepted Answer

Since the photosynthetic action spectrum of Halobacterium is complementary to that of green plants, it suggests that Halobacterium absorbs the wavelengths of light that green plants do not absorb effectively. Green plants absorb mainly blue and red light, but not much in the green range. Therefore, the best choice is E, which includes blue and red light.

Quiz 10: Photosynthesis