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4. Calculate the quantity of phosphate that was taken up into the yeast cells after 40 min incubation. (40 marks) This is calculated as follows: (i) The quantity of phosphate which was taken up into the yeast cells at any time is equal to the quantity of phosphate that was present at the beginning of the experiment minus the quantity left outside at 40 min incubation. (ii) To calculate the starting quantity (?moles) of phosphate in 15 ml of the initial incubation medium, use the information provided in the experimental section (ie, 10 ml of 1.5 mM potassium dihydrogen phosphate made up to 15 ml with yeast suspension, is __ ?moles in 15 ml). (iii) From your graph obtain the concentration (?mol/ml) of phosphate (in the supernatant) outside the cells at 40 min. Find the quantity of phosphate (?moles) in the 15 ml incubation mixture that remained outside the cells. (iv) By subtraction, determine the quantity of phosphate (?moles) that was taken up into the cells after 40 min incubation. NOTE: Do not confuse the quantity of phosphate (ie, ?moles) taken up into the yeast cell with the molarity (?M, or micromoles per litre) of the phosphate inside the yeast cells. To convert one to the other, you would need to know what the intracellular water volume of the yeast cell was, and you would also have to assume that (a) there was no phosphate inside the cell to start with, and (b) that all the phosphate taken up into the cell remained as inorganic phosphate and was not incorporated into other compounds.

          4. Calculate the quantity of phosphate that was taken up into the yeast cells after 40 min incubation. (40 marks)

This is calculated as follows:

(i) The quantity of phosphate which was taken up into the yeast cells at any time is equal to the quantity of phosphate that was present at the beginning of the experiment minus the quantity left outside at 40 min incubation.

(ii) To calculate the starting quantity (?moles) of phosphate in 15 ml of the initial incubation medium, use the information provided in the experimental section (ie, 10 ml of 1.5 mM potassium dihydrogen phosphate made up to 15 ml with yeast suspension, is __ ?moles in 15 ml).

(iii) From your graph obtain the concentration (?mol/ml) of phosphate (in the supernatant) outside the cells at 40 min. Find the quantity of phosphate (?moles) in the 15 ml incubation mixture that remained outside the cells.

(iv) By subtraction, determine the quantity of phosphate (?moles) that was taken up into the cells after 40 min incubation.

NOTE: Do not confuse the quantity of phosphate (ie, ?moles) taken up into the yeast cell with the molarity (?M, or micromoles per litre) of the phosphate inside the yeast cells. To convert one to the other, you would need to know what the intracellular water volume of the yeast cell was, and you would also have to assume that (a) there was no phosphate inside the cell to start with, and (b) that all the phosphate taken up into the cell remained as inorganic phosphate and was not incorporated into other compounds.

4. Calculate the quantity of phosphate that was taken up into the yeast cells after 40 min incubation. (40 marks)

This is calculated as follows:

(i) The quantity of phosphate which was taken up into the yeast cells at any time is equal to the quantity of phosphate that was present at the beginning of the experiment minus the quantity left outside at 40 min incubation.

(ii) To calculate the starting quantity (?moles) of phosphate in 15 ml of the initial incubation medium, use the information provided in the experimental section (ie, 10 ml of 1.5 mM potassium dihydrogen phosphate made up to 15 ml with yeast suspension, is ?moles in 15 ml).

(iii) From your graph obtain the concentration (?mol/ml) of phosphate (in the supernatant) outside the cells at 40 min. Find the quantity of phosphate (?moles) in the 15 ml incubation mixture that remained outside the cells.

(iv) By subtraction, determine the quantity of phosphate (?moles) that was taken up into the cells after 40 min incubation.

NOTE: Do not confuse the quantity of phosphate (ie, ?moles) taken up into the yeast cell with the molarity (?M, or micromoles per litre) of the phosphate inside the yeast cells. To convert one to the other, you would need to know what the intracellular water volume of the yeast cell was, and you would also have to assume that (a) there was no phosphate inside the cell to start with, and (b) that all the phosphate taken up into the cell remained as inorganic phosphate and was not incorporated into other compounds.

Added by Richard M.

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