Question 1

As climate change leads to drier and drier summers in the southeastern United States, more and more homeowners find that they have crabgrass growing in their yards. The reason for this is that

Accepted Answer

Crabgrass is a C4 plant, which means it is more efficient at photosynthesis in hot, dry conditions compared to C3 plants. This allows it to thrive in the drier summers caused by climate change.

Question 2

Which of the following events takes place in the Calvin cycle?

Accepted Answer

The Calvin cycle involves the conversion of carbon dioxide (CO2) into glyceraldehyde-3-phosphate (G3P), a three-carbon sugar, which is a key step in the synthesis of glucose in plants during photosynthesis. This process does not directly involve the transfer of electrons to photosystem I, the generation of ATP from ADP + P, the splitting of water, or the generation of NADPH from NADP+, which are parts of the light-dependent reactions of photosynthesis.

Question 3

Which compounds link the light reactions with the Calvin cycle reactions?

Accepted Answer

ATP and NADPH are the products of the light reactions of photosynthesis and are used as energy and reducing power, respectively, in the Calvin cycle to fix carbon dioxide into organic molecules.

Question 4

Which of the following organisms can perform photosynthesis?

Accepted Answer

Algae can perform photosynthesis, as they contain chlorophyll, which allows them to convert sunlight into energy, similar to plants.

Question 5

Why do plants contain other pigments besides chlorophyll?

Accepted Answer

The additional pigments in plants, such as carotenoids and phycobilins, absorb light in different parts of the spectrum than chlorophyll, allowing the plant to capture more of the sunlight's energy for photosynthesis.

Question 6

Inside the chloroplasts, chlorophyll is found in the

Accepted Answer

Chlorophyll, the pigment responsible for capturing light energy during photosynthesis, is located in the thylakoid membrane of chloroplasts. This placement allows it to effectively absorb sunlight and convert it into chemical energy.

Question 7

The innermost compartment of a chloroplast formed by the interconnected thylakoids is the

Accepted Answer

The thylakoid space, also known as the lumen, is the innermost compartment of a chloroplast formed by the interconnected thylakoids, where the light-dependent reactions of photosynthesis take place.

Question 8

How does ATP synthase obtain the energy to produce ATP?

Accepted Answer

ATP synthase produces ATP by utilizing the energy released when hydrogen ions (H+) flow down their concentration gradient from the thylakoid space into the stroma in chloroplasts (or from the intermembrane space into the matrix in mitochondria). This process is known as chemiosmosis.

Question 9

The production of glyceraldehyde 3-phosphate (G3P) in the Calvin cycle requires six molecules each of ATP and NADPH. Another three molecules of ATP are then used in the cycle. What is the purpose of these three additional ATP molecules?

Accepted Answer

The three additional ATP molecules are used to regenerate ribulose-1,5-bisphosphate (RuBP), the starter molecule for the Calvin cycle, allowing the cycle to continue.

Question 10

Chlorophyll is to the light reactions as ________ is to the Calvin cycle.

Accepted Answer

RuBP (ribulose bisphosphate) is a molecule that plays a crucial role in the Calvin cycle, similar to how chlorophyll is essential for capturing light energy in the light reactions.

Question 11

The light reactions act much as a battery to power the reactions of the Calvin cycle. This energy is stored as

Accepted Answer

The light reactions of photosynthesis generate ATP and NADPH, which are then used as energy sources for the Calvin cycle to synthesize glucose from carbon dioxide.

Question 12

The chlorophyll a molecules in the reaction center of a photosystem participate directly in the capture of solar energy. What is the purpose of the accessory pigments?

Accepted Answer

The answer of The chlorophyll a molecules in the reaction...

Question 13

Which of the following is a function specific to photosystemI?

Accepted Answer

Photosystem I is primarily involved in the production of NADPH, a molecule that plays a crucial role in the Calvin cycle of photosynthesis by providing the reducing power necessary for carbon fixation.

Question 14

During photosynthesis, ________ is oxidized, while ________ is reduced.

Accepted Answer

During photosynthesis, water is oxidized to oxygen, and carbon dioxide is reduced to form carbohydrates (sugars).

Question 15

In photosynthesis, the light reactions ________ while the Calvin cycle ________.

Accepted Answer

The light reactions of photosynthesis capture solar energy and convert it into chemical potential energy in the form of ATP and NADPH, which are then used by the Calvin cycle to fix carbon dioxide into organic molecules like glucose.

Question 16

The light reactions of photosynthesis are said to be similar to a battery because they form a current. In which direction do the electrons of this circuit flow?

Accepted Answer

The correct flow of electrons in the light reactions of photosynthesis starts from water (H2O), goes through Photosystem II (PSII), then through the electron transport chain to Photosystem I (PSI), through another segment of the electron transport chain, and finally to NADPH. This sequence correctly represents the Z-scheme of electron flow in the light-dependent reactions of photosynthesis.

Question 17

The products of photosynthesis are water and carbon dioxide.

Accepted Answer

The products of photosynthesis are oxygen and glucose, not water and carbon dioxide. Water and carbon dioxide are the reactants.

Question 18

In a redox reaction, reduction means ________, and oxidation means ________.

Accepted Answer

Reduction is the gain of electrons, while oxidation is the loss of electrons in a redox (reduction-oxidation) reaction.

Question 19

Thefluid-filled areawithin the chloroplast is called the

Accepted Answer

The stroma is the fluid-filled area within the chloroplast where the Calvin cycle (light-independent reactions) of photosynthesis takes place, distinct from the thylakoid membranes where the light-dependent reactions occur.

Question 20

The light reactions produce ________, which are used in the Calvin cycle. The Calvin cycle releases ________, which return to the light reactions.

Accepted Answer

The light reactions of photosynthesis produce ATP and NADPH, which are then used in the Calvin cycle. The Calvin cycle, in turn, releases ADP and NADP+ (not explicitly mentioned but implied as they are the depleted forms of ATP and NADPH), which return to the light reactions to be re-energized.

Quiz 6: Energy for Life