$$6 \mathrm{CO}_2 + 6 \mathrm{H}_2\mathrm{O} + \text{light energy} \rightarrow C_6H_{12}O_6$ + 6 \mathrm{O}_2$$

Question 1

Which of the following best describes the overall purpose of photosynthesis in the biosphere?

Accepted Answer

To convert light energy into the chemical energy of ATP and NADPH, which is then used to synthesize sugars

Question 2

Which equation correctly represents the overall process of photosynthesis?

Accepted Answer

$$6 \mathrm{CO}_2 + 6 \mathrm{H}_2\mathrm{O} + 	ext{light energy} ightarrow C_6H_{12}O_6$ + 6 \mathrm{O}_2$$

Question 3

During the light reactions of photosynthesis, what is the primary function of water?

Accepted Answer

To provide electrons to replace those lost by chlorophyll in photosystem II

Question 4

Which of the following best explains why the absorption spectrum of chlorophyll a does not fully match the action spectrum of photosynthesis?

Accepted Answer

Other pigments besides chlorophyll a also absorb light and contribute to photosynthesis

Question 5

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

Accepted Answer

It acts as a final electron acceptor, forming NADPH

Question 6

Which of the following statements about the Calvin cycle is correct?

Accepted Answer

It uses ATP and NADPH produced in the light reactions to reduce CO$$_2 to $$sugar

Question 7

A plant is exposed to light that is primarily green in wavelength. What is the most likely effect on the rate of photosynthesis, and why?

Accepted Answer

The rate will decrease because chlorophyll reflects green light rather than absorbing it

Question 8

Which of the following best describes the relationship between wavelength and energy in the electromagnetic spectrum?

Accepted Answer

As wavelength decreases, energy increases

Question 9

In the process of chemiosmosis during photosynthesis, where is the proton gradient established?

Accepted Answer

Across the thylakoid membrane, with a higher concentration of protons inside the thylakoid space

Question 10

Which enzyme is responsible for carbon fixation in the Calvin cycle, and why is it significant?

Accepted Answer

Rubisco; it is the most abundant protein on Earth and catalyzes the incorporation of CO$$_2$$ into organic molecules

Question 11

Photorespiration can be problematic for plants because:

Accepted Answer

It consumes O$$_2$$ and releases CO$$_2$$, reducing the efficiency of photosynthesis

Question 12

Which of the following is a key difference between C$$_3$$ and C$$_4$$ plants?

Accepted Answer

C$$_4$$ plants use PEP carboxylase to initially fix CO$$_2$$, reducing photorespiration

Question 13

Which of the following best explains why the light reactions and the Calvin cycle are separated in time in CAM plants?

Accepted Answer

To minimize water loss by opening stomata at night and fixing CO$$_2$$ then

Question 14

What is the main function of the light-harvesting complex in a photosystem?

Accepted Answer

To capture photons and transfer energy to the reaction-center chlorophyll

Question 15

Which of the following correctly describes the flow of electrons during the linear electron flow in the light reactions?

Accepted Answer

Water $$\rightarrow$$ Photosystem II $$\rightarrow$$ Electron Transport Chain $$\rightarrow$$ Photosystem I $$\rightarrow$$ NADP^+$

Question 16

How many molecules of ATP and NADPH are required to produce one net G3P molecule in the Calvin cycle?

Accepted Answer

$$9$$ ATP and $$6$$ NADPH

Question 17

Which of the following is a similarity between chemiosmosis in photosynthesis and cellular respiration?

Accepted Answer

Both use a proton gradient to drive ATP synthesis via ATP synthase

Question 18

Why is the enzyme PEP carboxylase important in C$$_4$$ plants?

Accepted Answer

It fixes CO$$_2$$ efficiently even when CO$$_2$$ concentrations are low, reducing photorespiration

Question 19

Which of the following statements best explains why green plants are considered autotrophs?

Accepted Answer

They produce their own organic molecules from inorganic CO$$_2$$ using energy from sunlight

Chapter 8: Photosynthesis – Study Guide and Key Concepts

Study Guide - Practice Questions