Question 1

If photosynthesizing green algae are provided with CO₂ containing heavy oxygen (18O), subsequent analysis will show that 18O is absent from which of the following molecules produced by the algae?

Accepted Answer

Oxygen gas (O₂) is produced during the light-dependent reactions of photosynthesis and is not involved in the fixation of CO₂, which produces molecules such as G3P and glucose. Therefore, if the CO₂ used by the algae contains heavy oxygen, it will not be incorporated into the O₂ released as a byproduct. The other molecules listed (G3P, glucose, and RuBP) are involved in the Calvin cycle, which fixes CO₂ and incorporates it into organic molecules. Therefore, these molecules will contain the heavy oxygen if it is present in the CO₂ used by the algae.

Question 2

In autotrophic bacteria, where are chlorophyll-like pigments located?

Accepted Answer

Autotrophic bacteria lack chloroplasts and therefore do not have chloroplast membranes or stroma. Instead, chlorophyll-like pigments are located in infolded regions of the plasma membrane, allowing for photosynthesis to occur.

Question 3

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

Accepted Answer

The absorption of light and its funneling to reaction-center chlorophyll a is the key event in the light reactions of photosynthesis. Option A is incorrect as NADP+ is reduced not produced. Option B is incorrect as ATP is actually produced in the light reactions. Option C refers to the dark reactions of photosynthesis (Calvin cycle) where carbon dioxide is fixed in organic molecules.

Question 4

If plants are grown in the light with CO₂ containing heavy oxygen (18O), subsequent analysis will show that 18O incorporated in organic molecules first appears in

Accepted Answer

The answer of If plants are grown in the light...

Question 5

If plants are grown with H₂O containing heavy oxygen (18O), subsequent analysis will show that 18O first appears in which of the following molecules produced by the algae?

Accepted Answer

When plants undergo photosynthesis, they consume water (H2O) and produce oxygen (O2). If the water contains heavy oxygen (18O), the oxygen that is produced during photosynthesis will also contain 18O. Therefore, the first molecule to contain 18O would be O2.

Question 6

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 7

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 then used by ATP synthase to generate ATP from ADP and inorganic phosphate.

Question 8

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 is to absorb and transfer light energy to the reaction-center chlorophyll, where it is used in the process of photosynthesis to synthesize ATP and NADPH. The pigment molecules do not split water or synthesize ATP directly, but rather they work to transfer energy within the thylakoid membrane to the reaction-center chlorophyll, which converts the light energy into chemical energy through a series of electron transfer reactions.

Question 9

What is the primary function of cyclic electron flow?

Accepted Answer

The primary function of cyclic electron flow is to produce additional ATP, which is achieved by recycling electrons from photosystem I back to the electron transport chain, generating a proton gradient for ATP synthesis.

Question 10

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

Photosystem II is responsible for the initial step of photosynthesis, which is the absorption of light energy to split water molecules and release oxygen. Therefore, if an organism lacks photosystem II, it will not produce oxygen in the light. Testing for the liberation of O₂ in the light would be the most accurate way to detect the absence of photosystem II.

Question 11

Where does the Calvin cycle take place?

Accepted Answer

The Calvin cycle takes place in the stroma of the chloroplast. This is where enzymes and other molecules involved in the cycle are located.

Question 12

What are the products of linear electron flow?

Accepted Answer

The products of linear electron flow are ATP and NADPH, which are both important energy molecules utilized in subsequent processes of photosynthesis. Heat and fluorescence are not direct products of linear electron flow, while ADP and NADP+ are reactants in the process, not products.

Question 13

Which of the following activities is associated with photosystem II?

Accepted Answer

The answer of Which of the following activities is associated...

Question 14

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

Accepted Answer

In chloroplasts, during chemiosmosis, protons flow from the thylakoid space into the stroma, driving ATP synthesis.

Question 15

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. What is the source of the extra ATP?

Accepted Answer

Cyclic electron flow generates additional ATP without producing NADPH, which explains the extra ATP consumed by the Calvin cycle.

Question 16

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 acidic interior and alkaline exterior create a proton gradient across the thylakoid membrane, which can drive ATP synthesis even in the dark.

Question 17

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, ATP and NADPH, are utilized in the Calvin cycle to power the synthesis 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, not products, of the light reactions. ADP, ℗i, and NADP+ are also not products of the light reactions, but rather are converted into ATP and NADPH during these reactions. Electrons and H+ are involved in the light reactions, but they are not utilized in the Calvin cycle.

Question 18

If photosynthesizing green algae are provided with CO₂ containing heavy oxygen (18O), subsequent analysis will show that 18O first appears in which of the following molecules produced by the algae?

Accepted Answer

The heavy oxygen (18O) will first appear in the molecule 3-phosphoglycerate. This is because in the first step of the Calvin cycle, the enzyme rubisco catalyzes the carboxylation of RuBP with CO₂ to form 2 molecules of 3-phosphoglycerate, and the oxygen in CO₂ becomes incorporated into the organic molecule. Therefore, any 18O in the CO₂ will be first incorporated into 3-phosphoglycerate.

Question 19

Which of the following is directly associated with photosystem I?

Accepted Answer

Photosystem I receives electrons from the thylakoid membrane electron transport chain, which is part of the light-dependent reactions in the process of photosynthesis.

Question 20

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

Accepted Answer

Oxygen gas is produced by splitting of water molecules during the light-dependent reactions of photosynthesis, which occur in photosystem II.

Quiz 8: Photosynthesis

If photosynthesizing green algae are provided with CO₂ containing heavy oxygen (18O) , subsequent analysis will show that 18O is absent from which of the following molecules produced by the algae?