They accumulate inside the cells by ion trapping due to low permeability of the membranes to the dissociated species. Ion trapping requires a gradient between the external water pH and intracellular pH ouch that the pH of water is lower than the cytoplasm PH. It can be seen from the experimental results that at water pH 6 transfusion has the highest objectification factor, which indicates that at this pH, it crosses the membrane more readily than momentously-methyl and chloroforms. However when the water pH decreases to 5. And 5, chloroforms have the highest objectification factor of 36 and 53, respectively. The higher the objectification factor, the greater the concentration of the chemical in the alga to that in water and therefore a greater amount of the neutral form of the herbicide crosses the membranes and accumulates in the algae. In contrast to chloroforms, momentously-methyl has the lowest objectification at water pH 6, 5. 3, and 5. This suggests a lower percent of the neutral form of momentously-methyl at each given water pH and less accumulation of the chemical in the algae due to its PC value of 3. 3.

In general, it can be seen that a higher PC value of the chemical, the higher the objectification factor or the higher the amount of the chemical in its neutral form for crossing the membrane readily. This is true for momentously-methyl (PC = 3. 3) and transfusion (PC = 4. 6) with similar molecular weight of 381. 37 and 401. 3, respectively. However, chloroforms (PC = 3. 7) appears to cross the membrane most readily and accumulating the most in the algae due to its small molecular weight of 357. 78 which may attribute to a smaller sized molecule for faster speed and permeability across the membrane.

In addition, chloroforms has very low photolytic degradation, allowing for its greater accumulation in the algae. 5, momentously-methyl had the highest objectification factor and transfusion had the lowest objectification factor. The observations are based only on pH control and indicate that there is greater accumulation of momentously-methyl than the other woo sulfonamides and that transfusion accumulated the least in the algae. In addition, the expected objectification factors are much higher than experimental objectification factors due to reasons explained in Q. 5.

A lower concentration of chloroforms is needed to inhibit the growth at pH 5 than pH 6. 5 because of a lower EXEC for the inhibition of growth at pH 5 was 44. 0 mol/L. EXEC is a common measure of the drugs potency. It is the half maximal effective concentration of a drug that induces a response halfway between the baseline and maximum effect after a specified exposure time. Comparison of the EXEC values and the effect curves shows that the algal toxicity of chloroforms was enhanced by about 25 fold when the pH was lowered from 6. 5 to 5 which can compensate for the use of a lower concentration of the herbicide.

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In addition, chloroforms caused 100% growth inhibition at a lower concentration (approve. 125 mol/L) at pH 5 compared to a higher concentration (approve. 10,000 mol/L) required at pH 6. 5. This results from a greater percentage of the neutral form of chloroforms (PC = 3. 7) at pH 5 that can cross the algal membranes readily. The need of a lower concentration of chloroforms to inhibit Roth of the algae is also consistent with the answer in Q as the experimental objectification factor was enhanced by about 6. 6 fold from a factor of 8 at pH 6 to a factor of 53 at pH 5 and the expected objectification factor was enhanced by about 9. Fold from a factor of 12. 53 at pH 6 too factor of 119. 94 at pH 5. The increase in concentration of undomesticated or neutral form of the herbicide causes a greater amount of the herbicide to cross the membrane and as a result, to achieve maximal growth inhibition, a lower concentration of the herbicide can be used to achieve the same effective objectification factor. The experimental objectification values were much lower than the expected values due to several reasons other than pH that can control the amount of the chemical in algae.

This can be attributed to the permeability of the algal membrane to the different chemicals based on different molecular weight and chemical structure. The neutral form of the chemical may leak out of the cell membrane by diffusion. The algae may use special pumps and transporters on its cell membrane to excrete waste and foreign molecules. The chemical may also be lost due to beatifications of the radioactive-labeled chemical into an undetected product.


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