GCSE Biology (AQA)

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Rate of Water Uptake

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Cell Biology Transport in Cells

Rate of Water Uptake

2:56 Osmosis
Spec 4.1.3.2
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  • Water uptake rate can be measured by osmosis in different concentrations using a calculation.
  • The formula for water uptake in grams per hour is: mass change in grams multiplied by 60, divided by time in minutes.
  • Simple compound measures like grams per hour are used to express the rate of water uptake.
  • Example using a potato: cylinders are cut using a cork borer, weighed, placed in different concentrations of sugar or salt, observed for water uptake rates, and then reweighed.
  • This practical experiment can be conducted at school or at home.
  • To measure the rate of water uptake, calculate the hourly rate of water uptake of plant tissue at a specific sucrose concentration.
  • Record the final mass after 30 minutes, calculate the change in mass over the recorded time.
  • Positive change in mass indicates water absorption by the potato cylinder through osmosis from the surrounding solution.
  • Higher values indicate more water absorbed by the plant tissue.
  • Negative change in mass at higher sucrose concentrations indicates mass loss from the potato cylinder.
  • Calculate the change in mass by subtracting the initial mass of the potato cylinder from the final mass.
  • Insert values into the formula to calculate the hourly uptake.
  • Ensure correct units (grams per hour) are used in calculations.
  • It's important to be able to perform simple calculations to determine the rate of water uptake.

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