Question 1

According to this figure, how do hydrogen ions make their way from the stroma to the thylakoid interior?

Accepted Answer

The answer of According to this figure, how do hydrogen...

Question 2

After reading the paragraph below, answer the questions that follow.
The graph below shows records of temperature (light gray line) and CO₂ (dark gray line) over the past 1,000 years. CO₂ is recorded in parts per million (ppm).
 
-If the trends shown in the graph continue, how might this affect photosynthesis?

Accepted Answer

The graph shows an increase in CO₂ levels, which would lead to an increase in photorespiration and a decrease in photosynthetic production of sugar. This is because in high CO₂ environments, plants have less of a need to take in CO₂, so they close their stomata. However, when the stomata are closed, the O₂ concentration inside the plant exceeds the CO₂ concentration, which causes photorespiration.

Question 3

After reading the paragraph below, answer the questions that follow.
The graph below shows records of temperature (light gray line) and CO₂ (dark gray line) over the past 1,000 years. CO₂ is recorded in parts per million (ppm).
 
-If you focus on the data from the mid-1900s (indicated by the arrow)through today, the graph shows that

Accepted Answer

The graph shows that when CO₂ levels are high, temperature is also high, indicating a correlation between the two. This can be observed from the mid-1900s onwards.

Question 4

After reading the paragraph below, answer the questions that follow.
The graph below shows records of temperature (light gray line) and CO₂ (dark gray line) over the past 1,000 years. CO₂ is recorded in parts per million (ppm).
 
-Currently, atmospheric CO₂ levels are approximately 400 ppm. The annual mean growth rate in CO₂ is about 2 ppm/year. Assuming this trend continues, what would you predict the CO₂ level to be in 100 years?

Accepted Answer

The graph shows that CO₂ levels have been steadily increasing over the past 1,000 years, with a more rapid increase in recent decades. The annual growth rate of 2 ppm/year indicates that in 100 years, CO₂ levels would increase by 200 ppm (2 ppm/year x 100 years). Therefore, the predicted CO₂ level in 100 years would be 400 ppm (current level) + 200 ppm (increase in 100 years) = 600 ppm. Choice C is the only option that matches this prediction.

Question 5

It has been suggested that global warming could be halted by fertilizing the oceans to increase the growth of algae. How might this affect the greenhouse effect?

Accepted Answer

Algal photosynthesis involves the uptake of CO₂ and production of O₂. By increasing the growth of algae via ocean fertilization, more CO₂ would be consumed, leading to a reduction in atmospheric CO₂ concentrations. This would ultimately decrease the greenhouse effect, as CO₂ is a major contributor to this phenomenon.

Question 6

Purple sulfur bacteria are organisms capable of photosynthesis. They get their name, in part, because they use H₂S (hydrogen sulfide)instead of water during the light reactions. In what form would you expect to find sulfur (S)as a result of photosynthesis in these bacteria?

Accepted Answer

Purple sulfur bacteria oxidize hydrogen sulfide (H₂S) to elemental sulfur (S₈ or S) during photosynthesis.

Question 7

Atrazine is a widely used herbicide that binds to a protein in photosystem II, ultimately causing a breakdown in electron transport. Atrazine would first inhibit the production of

Accepted Answer

Atrazine inhibits the production of ATP by binding to a protein in photosystem II, causing a breakdown in electron transport. This ultimately results in decreased production of ATP, which is necessary for many cellular processes, including photosynthesis.

Question 8

Put the following steps of the Calvin cycle in the correct order: 1. Carbon fixation
2) Regeneration of RuBP
3) Release of G3P
4) Reduction

Accepted Answer

The Calvin cycle starts with carbon fixation, followed by reduction, then the release of G3P, and finally the regeneration of RuBP.

Question 9

Put the following steps of the light reactions in the correct order: 1. Light excites an electron from photosystem I.
2) Light excites an electron from photosystem II.
3) Electrons reduce NADP⁺ to NADPH.
4) Electrons pass through an electron transport chain, which generates a H⁺ gradient used to make ATP.

Accepted Answer

The correct order of the light reactions is 2, 4, 1, 3. Photosystem II is the first step, followed by the electron transport chain that generates a gradient used to make ATP. Then, photosystem I excites an electron, which is used along with electrons from photosystem II to reduce NADP⁺ to NADPH.

Question 10

Ozone consists of ________ oxygen atom(s).

Accepted Answer

Ozone consists of three oxygen atoms, making its chemical formula O3.

Question 11

Which of the following is not an expected outcome of global climate change?

Accepted Answer

Global climate change is expected to cause extreme weather patterns, spread of tropical diseases, and increased extinction rates among other consequences. However, lower sea levels are not an expected outcome as the melting of polar ice caps and glaciers is actually causing sea levels to rise.

Question 12

In this drawing of a chloroplast, which structure represents the thylakoid membrane?

Accepted Answer

The answer of In this drawing of a chloroplast, which...

Question 13

Which of the following has been a major source of ozone destruction over the past 50 years?

Accepted Answer

Chlorofluorocarbons (CFCs) have been a major source of ozone destruction over the past 50 years. When CFCs are released into the atmosphere, they react with ozone, breaking down the ozone molecules and depleting the ozone layer.

Question 14

It has been argued that cutting old-growth forests and replacing them with plantations of young trees would help to alleviate the threat of global greenhouse warming. What important fact does this argument ignore?

Accepted Answer

Cutting old-growth forests releases stored carbon into the atmosphere, increasing CO₂ levels, which contributes to global warming.

Question 15

Chlorophyll is located in ________, which are found in ________, which are concentrated in ________.

Accepted Answer

Chlorophyll is located in thylakoids, which are membrane-bound compartments inside chloroplasts. Chloroplasts are found in the mesophyll cells of leaves, which is the primary site of photosynthesis in plants.

Question 16

You want to use radioactively labeled oxygen to trace carbon fixation in a plant. You should incorporate the radioactively labeled oxygen into

Accepted Answer

Carbon fixation is the process by which atmospheric carbon dioxide is converted into organic compounds by plants. The oxygen in CO₂ is incorporated into the organic compounds during carbon fixation, so choosing option B - CO₂ - as the source of radioactively labeled oxygen is the best option for tracing carbon fixation in the plant.

Question 17

Red algae are found in relatively deep water. In order for light to penetrate to these depths, it must be high in energy. Which wavelengths of light would you expect red algae to use?

Accepted Answer

Blue light has the shortest wavelength and highest energy, making it more able to penetrate deeper into water. Therefore, it is likely that red algae would use blue or blue-green light for photosynthesis.

Question 18

After reading the paragraph below, answer the questions that follow.
You're conducting an experiment to determine the effect of different wavelengths of light on the absorption of carbon dioxide as an indicator of the rate of photosynthesis in aquatic ecosystems. If the rate of photosynthesis increases, the amount of carbon dioxide in the environment will decrease, and vice versa.
Small aquatic plants are placed into three containers of water mixed with carbon dioxide. Container A is placed under normal sunlight, B under green light, and C under red light. The containers are observed for a 24-hour period.
-Based on your knowledge of the process of photosynthesis, the plant in the container placed under red light would probably

Accepted Answer

Red light is more effective for photosynthesis than green light, as chlorophyll absorbs red light more efficiently, leading to higher CO₂ absorption.

Question 19

Many of the regions of the world where hunger is prevalent are also regions with hot and dry climates. What types of agricultural crops would you suggest that these regions attempt to grow?

Accepted Answer

C₄ plants and CAM plants are more efficient in hot and dry climates due to their specialized photosynthetic pathways that minimize water loss and maximize water use efficiency.

Question 20

Ozone

Accepted Answer

Ozone is a molecule composed of three oxygen atoms (O3). It is found in the stratosphere, a layer of Earth's atmosphere between 10 and 50 kilometers above the surface. Ozone absorbs most of the sun's harmful ultraviolet (UV) radiation, preventing it from reaching the surface of the planet where it can cause skin cancer, cataracts, and other problems. This is why ozone is often referred to as "Earth's sunscreen." However, ozone depletion occurs due to human activities, such as the emission of chlorofluorocarbons (CFCs), which can break down ozone molecules. Therefore, A is incorrect. Carbon dioxide does not break down ozone; in fact, carbon dioxide and other greenhouse gases can contribute to global warming, which affects the concentration of ozone in the atmosphere. Also, while oxygen is a component of ozone, it is not a source of oxygen for cellular respiration. Therefore, C is also incorrect.

Quiz 7: Photosynthesis: Using Light to Make Food