INVESTIGATION – Why are cells so small?
AIM: Determine which cell size allows the best /quickest absorption or excretion of substances from a cell,
using modelling of absorption.
RESEARCH QUESTION: What cell size would absorb nutrients the fastest?
HYPOTHESIS: IF a cell is _____________________________________________ , THEN the
time taken to absorb nutrients will be _________________________, because ______________
________________________________________________________________________________.
Materials:
0.1M 150ml sulphuric acid
paper towel
1 x 250ml beaker
1 x gelatine cube 1cm3 stained with phenolphthalein
stopwatch
1 x gelatine cube 2cm3 stained with phenolphthalein
plastic spoon
METHOD AND RESULTS
●
Carefully collect your two ‘cells’ and place them in the bottom of your empty beaker, using the
spoon to carefully lower them without damaging them.
● Pour the sulphuric acid gently over the two ‘cells’ until they are covered.
● As soon as the ‘cells’ are covered, start timing with the stopwatch.
● Make a note of the time that has passed when the first ‘cell’ has lost all its pink colour.
● Continue timing until the second ‘cell’ has lost all its pink colour.
● Make sure you write your times accurately in the results table below.
PRIMARY DATA
‘Cell’ size
SECONDARY DATA
Time until colourless
Time measured by
(min:sec)
another group (min:sec)
Difference in times
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DISCUSSION:
1. Evaluate your hypothesis. Did you prove or disprove your hypothesis? Explain.
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2. Which ‘cell’ size absorbed the substance the quickest? Why do you think this happened?
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3. Where in the human body do you think this adaptation would best be suited, the skin or the small
intestine? Explain your answer.
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