Q: Which equation correctly represents the overall process of photosynthesis?

$$6CO_2 + 6H_2O + \text{light energy} \rightarrow C_6H_{12}O_6$ + 6O_2$$

Question 1

Which of the following best describes the role of water in the light reactions of photosynthesis?

Accepted Answer

Water donates electrons to P680+ in photosystem II, becoming oxidized to O2.

Question 2

Which equation correctly represents the overall process of photosynthesis?

Accepted Answer

$$6CO_2 + 6H_2O + 	ext{light energy} ightarrow C_6H_{12}O_6$ + 6O_2$$

Question 3

In the methane combustion reaction shown, which molecule acts as the reducing agent?

Accepted Answer

$$CH_4$$

Question 4

Why do leaves appear green to our eyes?

Accepted Answer

Chlorophyll reflects and transmits green light while absorbing violet-blue and red light.

Question 5

Which pigment is primarily responsible for the absorption of light energy used in photosynthesis?

Accepted Answer

Chlorophyll a

Question 6

What is the main function of accessory pigments such as chlorophyll b and carotenoids in the chloroplast?

Accepted Answer

They broaden the spectrum of light that can be used for photosynthesis and protect chlorophyll from damage.

Question 7

Which of the following statements about redox reactions is correct?

Accepted Answer

Reduction is the gain of electrons, and oxidation is the loss of electrons.

Question 8

During the light reactions, what is the immediate fate of the electrons lost from the reaction center chlorophyll a (P680) in photosystem II?

Accepted Answer

They are transferred to the primary electron acceptor (pheophytin).

Question 9

Which of the following best explains why the combustion of methane is considered an energy-yielding redox reaction?

Accepted Answer

Electrons are transferred from methane to oxygen, and the electrons lose potential energy as they move to a more electronegative atom.

Question 10

Which of the following wavelengths of light is most effective for driving photosynthesis, based on the absorption spectra of chloroplast pigments?

Accepted Answer

Red (650–700 nm) and violet-blue (400–500 nm)

Question 11

What is the role of NADP+ in the light reactions of photosynthesis?

Accepted Answer

It acts as the final electron acceptor, becoming reduced to NADPH.

Question 12

Which of the following best describes the energy changes that occur when an electron is transferred from a less electronegative atom to a more electronegative atom?

Accepted Answer

The electron loses potential energy, and energy is released.

Question 13

Which of the following is a correct description of the Z scheme in photosynthesis?

Accepted Answer

It describes the linear flow of electrons from water to NADP+ through both photosystems, with a characteristic drop and rise in electron energy.

Question 14

A plant is exposed only to green light. What is the most likely outcome for its rate of photosynthesis?

Accepted Answer

It will decrease because chlorophyll reflects green light.

Question 15

Which of the following statements about the structure of chlorophyll a is correct?

Accepted Answer

It contains a porphyrin ring with a central magnesium atom and a hydrocarbon tail.

Question 16

Which of the following best explains why the Calvin cycle is considered an endergonic process?

Accepted Answer

It requires the input of energy from ATP and NADPH to fix carbon dioxide into carbohydrates.

Question 17

Which of the following is NOT a product of the light reactions of photosynthesis?

Accepted Answer

Glucose

Question 18

What is the immediate consequence if the water-splitting enzyme in photosystem II is inhibited?

Accepted Answer

No oxygen will be produced, and the electron flow from PSII will stop.

Question 19

Which of the following best describes the fate of photons absorbed by chlorophyll in the thylakoid membrane?

Accepted Answer

Their energy is transferred to electrons, raising them to an excited state.

LEC 11: Photosynthesis: Mechanisms, Redox Reactions, and Light Absorption

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