Question 1

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 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

In the thylakoid membranes, what is the main role of the pigment molecules in a light-harvesting complex?

Accepted Answer

The main role of pigment molecules in a light-harvesting complex (also known as antenna complex) is to absorb energy from sunlight and transfer it to the reaction-center chlorophyll. The reaction-center chlorophyll uses this energy to initiate photosynthesis.

Question 4

Which statement describes the functioning of photosystem II?

Accepted Answer

Photosystem II functions by using light energy to excite electrons in the thylakoid membrane, which are then passed along to a reaction-center chlorophyll. The P680 chlorophyll then donates a pair of electrons to a mobile electron carrier, and the electron vacancies in P680+ are filled by electrons derived from water. This process also releases oxygen as a by-product. Finally, the mobile electron carrier passes the electrons to the thylakoid membrane electron transport chain, which creates a proton gradient that drives ATP synthesis.

Question 5

What are the products of linear electron flow?

Accepted Answer

Linear electron flow results in the production of ATP and NADPH through the movement of electrons from water to NADP+. Heat and fluorescence are not products of linear electron flow, and P700 and P680 are not produced but rather serve as the reaction centers in photosystem I and II, respectively. ADP and NADP+ are also not products of linear electron flow, as they are the starting molecules that are transformed into ATP and NADPH through the flow of electrons.

Question 6

If photosynthesizing green algae are provided with CO2 containing heavy oxygen (18O), later analysis will show that all of the following molecules produced by the algae contain 18O except

Accepted Answer

Oxygen produced during photosynthesis comes from water, not CO2.

Question 7

In autotrophic bacteria, where is chlorophyll located?

Accepted Answer

Unlike plants and algae, autotrophic bacteria lack chloroplasts. Instead, they have infolded plasma membranes that contain the pigments necessary for photosynthesis, including chlorophyll. Therefore, the correct answer is E) in the infolded plasma membrane.

Question 8

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

Accepted Answer

The electron transport chain in plant cells is located on the thylakoid membranes of chloroplasts. This is where photosynthesis takes place, and the electron transport chain is necessary for the production of ATP during photosynthesis.

Question 9

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

Accepted Answer

ATP and NADPH are both products of the light reactions of photosynthesis that are utilized in the Calvin cycle to power the production of glucose. CO2 is also utilized in the Calvin cycle, but it is not a product of the light reactions. H2O and O2 are reactants in the light reactions, and ADP, ℗i, and NADP+ are not products of the light reactions but rather are molecules that are transformed and reused in the light reactions. Electrons and H+ are also involved in the light reactions but do not directly participate in the Calvin cycle.

Question 10

In any ecosystem, terrestrial or aquatic, which of the following are always necessary?

Accepted Answer

Autotrophs are always necessary in any ecosystem as they produce their own food through photosynthesis or chemosynthesis. Heterotrophs depend on autotrophs for their food, and hence they are also necessary, but not always present in an ecosystem. Producers like green plants and photosynthesizers are also necessary, but autotrophs cover a broader category that includes non-green plants, like chemosynthetic bacteria. Hence, D is the best choice.

Question 11

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, which drives the synthesis of ATP by ATP synthase. This process is similar to the chemiosmotic process in mitochondria, where a proton gradient is established across the inner mitochondrial membrane, driving the synthesis of ATP.

Question 12

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

Accepted Answer

ATP synthase complexes are located in the thylakoid membrane of chloroplasts, where they are involved in photosynthesis, and in the inner mitochondrial membrane, where they are involved in cellular respiration. They are not located in the plasma membrane or on the outer mitochondrial membrane. Therefore, the best choice is D, as it includes both the thylakoid membrane and the inner mitochondrial membrane.

Question 13

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

Accepted Answer

In chloroplasts, chemiosmosis translocates protons from the stroma to the thylakoid space. This gradient is established during photosynthesis as electrons move through the electron transport chain in the thylakoid membrane, pumping protons into the thylakoid space. As the protons diffuse back into the stroma through ATP synthase, ATP is produced.

Question 14

Which of the following events occurs in the light reactions of photosynthesis?

Accepted Answer

The event that occurs in the light reactions of photosynthesis is the absorption of light, which is then funneled to reaction-center chlorophyll a. This process ultimately leads to the production of ATP and NADPH, which are used in the Calvin cycle to produce carbohydrates. Choices A, B, C, and D are events that occur in other parts of photosynthesis, but not in the light reactions specifically.

Question 15

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

Liberation of O2 in the light is a direct product of photosystem II in photosynthesis. If an organism lacks photosystem II, it will not produce O2 in the light. Therefore, testing for liberation of O2 in the light is the best way to detect the lack of photosystem II in these organisms.

Question 16

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

Accepted Answer

Photosynthesis is the process by which plants convert light energy into chemical energy and store it in complex organic molecules such as glucose. Respiration, on the other hand, is the process by which cells release the stored energy by breaking down these organic molecules and converting them into ATP. In other words, photosynthesis stores energy, while respiration releases it.

Question 17

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 can produce additional ATP without the consumption of NADPH. This occurs when photosystem I produces additional ATP by taking electrons from the electron transport chain and returning them to the reaction center. Therefore, the extra ATP in this scenario likely came from cyclic electron flow.

Question 18

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

Accepted Answer

Oxygen is released during photosynthesis as a by-product of the light-dependent reactions in which water molecules are split into oxygen, protons, and electrons.

Question 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?

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 20

Where does the Calvin cycle take place?

Accepted Answer

The Calvin cycle takes place in the stroma of the chloroplast, which is the fluid-filled space surrounding the grana where the thylakoid membrane is located. The stroma contains the enzymes and other molecules necessary for the reactions of the Calvin cycle to occur.

Quiz 8: Photosynthesis