Question
Figure 2 shows part of in leaf Molecules of carbon dioxide diffuse from the air into the mesophyll cells. Which two changes will increase the rate at which carbon dioxide diffuses into the mesophyll cells? [2 marks] Tick (surd ) two boxes Decreased number of chloroplasts in the cells square Decreased surface area of cells in contact with the air square increased carbon dioxide concentration in the air square increased number of stomata that are open square increased oxygen concentration in the air square
Answer
4.1
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Aria
Professional · Tutor for 6 years
Answer
The two changes that will increase CO2 diffusion into the mesophyll cells are the increased carbon dioxide concentration in the air and the increased number of stomata that are open.
Explanation
## Understanding the problem The rate of diffusion of any substance across a membrane depends on properties like the concentration gradient, the surface area for diffusion, the environmental temperature, and the presence of any facilitating units. The question asks us to determine which changes will lead to an increased rate of carbon dioxide (CO2) diffusion into mesophyll cells in plants.## Properties of DiffusionGenerally, an increase in diffusion will be facilitated by a higher concentration gradient, an increased contact surface area, or mechanisms bolstering easy passage into the intended region.Diffusion proceeds from a region with a higher concentration to one with a lower concentration. Thus, a higher concentration of CO2 in the outside atmosphere (likely resulting from an increased number of open stomata) will improve its rate of diffusion since more gas molecules would move from outside to replace the consumed CO2 molecules inside the mesophyll cells.Furthermore, stomata are the chief venues which CO2 utilizes to get into plants from the environment; if more of these small pores are open simultaneously, a higher influx of CO2 into the plant can be expected, driving up respiration and photosynthesis rates.On the flip side, with a decrease in the number of chloroplasts and/or a decreased surface area, the rate of diffusion will likely decrease. This is 'cause the surface area forms the direct contact area with the atmospheric air for gaseous exchange, and reducing it will let fewer CO2 molecules to enter. Farther decrease in chloroplasts will imply that fewer CO2 molecules are biologically useful inside the cell, reducing a potential increase in concentration gradient encouraging additional CO2 diffusion into cells.