CAM (crassulacean acid metabolism) plants such as the cacti differ from standard C4 plants such as corn in which of the following ways?
a. CAM plants minimize photorespiration whereas C4 plants do not.
b. CAM plants use both mesophyll and bundle sheath leaf cells for photosynthesis whereas C4 plants do not.
c. CAM plants are more efficient at producing sugar than C4 plants regardless of environmental conditions.
d. CAM plants produce a 4-carbon molecule in the first step of carbon fixation, but C4 plants do not.
e. CAM plants are limited to producing CO2 for the Calvin cycle during the day, while C4 plants produce CO2 for the Calvin cycle both during the day and at night.
I think the correct answer is E.
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Which of the following has the highest photosynthetic efficiency in hot and dry environments?
a. C3 plants
b. C4 plants
c. plants undergoing photorespiration
d. plants that use oxygen to produce sugars
e. plants that only produce sugar in the dark
This one I'm not sure about at all. Any help is greatly appreciated.
B for the second question
For the first question, you are correct. The correct answer is E.
CAM (crassulacean acid metabolism) plants are characterized by their ability to open their stomata at night, taking in carbon dioxide (CO2) and fixing it into a four-carbon molecule. This molecule is then stored in vacuoles and released during the day to be used for the Calvin cycle, the process by which CO2 is used to produce sugars.
C4 plants, on the other hand, use a different pathway where they initially fix CO2 into a four-carbon molecule in specialized mesophyll cells. This molecule is then transported to bundle sheath cells, where it is decarboxylated to release CO2 for use in the Calvin cycle.
Therefore, the major difference between CAM and C4 plants is that CAM plants only produce CO2 for the Calvin cycle during the day, while C4 plants produce CO2 for the Calvin cycle both during the day and at night.
Now, for the second question:
In hot and dry environments, where water availability is limited, C4 plants have a higher photosynthetic efficiency compared to C3 plants. This is because C4 plants have a more efficient carbon concentration mechanism that minimizes the loss of water through transpiration. They separate the initial CO2 fixation step from the Calvin cycle, thereby reducing photorespiration and conserving water.
On the other hand, C3 plants do not have this carbon concentration mechanism and are more prone to photorespiration, which can lead to the loss of water. Photorespiration occurs when the enzyme Rubisco, involved in CO2 fixation, reacts with oxygen instead of CO2, resulting in the release of CO2 and consumption of energy.
Therefore, the correct answer is b) C4 plants. They have higher photosynthetic efficiency in hot and dry environments due to their water-conserving carbon concentration mechanism.
To answer the first question regarding CAM (crassulacean acid metabolism) plants and C4 plants, let's go through each option:
a. CAM plants minimize photorespiration whereas C4 plants do not.
To determine if this statement is true, we need to understand the role of photorespiration in CAM and C4 plants. Photorespiration is a process that can occur in plants under certain conditions, leading to a loss of efficiency in photosynthesis. Both CAM and C4 plants have adaptations that minimize photorespiration, so this option is not the correct answer.
b. CAM plants use both mesophyll and bundle sheath leaf cells for photosynthesis whereas C4 plants do not.
This statement is accurate. CAM plants use both mesophyll and bundle sheath leaf cells for photosynthesis, while C4 plants only use bundle sheath cells. However, this difference does not relate to the question about photorespiration, so this option is not the correct answer.
c. CAM plants are more efficient at producing sugar than C4 plants regardless of environmental conditions.
The efficiency of sugar production is not specifically related to the differences between CAM and C4 photosynthesis. Hence, this option is not the correct answer.
d. CAM plants produce a 4-carbon molecule in the first step of carbon fixation, but C4 plants do not.
This statement is true. CAM plants initially produce a 4-carbon molecule (malate or oxaloacetate) during carbon fixation, while C4 plants produce a 4-carbon molecule (oxaloacetate) in their carbon fixation pathway. This is the correct answer.
e. CAM plants are limited to producing CO2 for the Calvin cycle during the day, while C4 plants produce CO2 for the Calvin cycle both during the day and at night.
This statement is not accurate. Both CAM and C4 plants have adaptations that allow them to store and release CO2 at different times, leading to efficient photosynthesis in different environmental conditions. Therefore, this option is not the correct answer.
Therefore, the correct answer to the first question is d. CAM plants produce a 4-carbon molecule in the first step of carbon fixation, but C4 plants do not.
Moving on to the second question about photosynthetic efficiency in hot and dry environments:
a. C3 plants
b. C4 plants
c. plants undergoing photorespiration
d. plants that use oxygen to produce sugars
e. plants that only produce sugar in the dark
In hot and dry environments, where water availability is limited, C4 plants tend to have higher photosynthetic efficiency compared to C3 plants. C4 plants have physiological adaptations that help reduce water loss through transpiration, making them more efficient in such conditions. Hence, the correct answer is b. C4 plants.
Options c, d, and e are not direct adaptations for hot and dry environments and do not necessarily improve photosynthetic efficiency. Hence, they are not the correct answers.
Therefore, the correct answer to the second question is b. C4 plants.