Benson Cheng
4A Bio Linzel
Grant Proposal
Diffusion Of Agar Cubes
Introduction:
The purpose of the experiment is to find out if the surface area and the volume of a
cell affect the ability of molecules to diffuse into the cellular space. In this lab, Agar
cubes are used to represent cells and the cytoplasm (volume) and the cell membrane
(surface area). Multiple trials are conducted to get the 2most precise data. Precision
is how close are the results of each of the trials of the experiment. Different from
precision, accuracy is how close are the data to the true value that had already been
proven. There are independent, dependent variables, and controls. Independent
variable is the inconsistent variable that is being changed and the one is being tested.
The dependent variable is the one that is being kept consistent and it relies on the
independent variable. Controls are the aspects of the experiment that are kept the
same.
Hypothesis:
The cube with the largest surface area will have the most molecules diffused into the
agar cube because the more surface area a cube have, the more molecules the agar
cube is getting per minute and thus the rate of diffusion will be faster.
Variables:
Independent variable: The surface area/ volume of the cubes
Dependent variable: The amount of molecules that diffused into the cube
Controls: The amount of time the cubes are in the Sodium Hydroxide solution,
Procedure:
1) Acquire 1000ml of distilled water and mix 8% of the water’s mass of Agar
powder. Pour the agar powder in the distilled water and boil the solution while
mixing the solution with a stirrer. Add approximately 1 teaspoon of
Phenolphthalein to the solution. As the solution started to produce small
bubbles, pour it out into a metal tray and put it in the freezer for 24 hours.
2) Take the metal tray containing the solidified agar out, and cut it into cubes
(1x1x1, 1.5x1.5x1.5, 2x2x2 [3 for each size]).
3) Obtain 50ml of Sodium hydroxide and 500 ml of distilled water. Stir with
stirrer for a minute.
4) Sink one cube of each size in the sodium hydroxide for 10 minutes
5) Cut each cube into half and measure the length, height, and width. Collect the
data.
6) Repeat step 4 three times.
Benson Cheng
4A Bio Linzel
Grant Proposal
Data Collection:
Data Processing / Analysis:
3 trials were made using 3 different sized cubes, each one representing a process of
diffusion occurring in different sized cells. To find out the amount of molecule that
diffused into the cube is to subtract the surface area and volume of the cubes after
diffusion form the original surface area and volume of the cube before diffusion
(Original SA/V – SA/V after diffusion= Volume diffused into the cube).
Trial 1:
1x1: 1.0-0.5= 0.5
1.5x1.5: 3.4-4.9= -1.5 (ERROR)
2x2: 8.0-4.9= 3.1
Trial 2:
1x1: 1.0-0.7= 0.3
1.5x1.5: 3.4-3.4= 0 (ERROR)
2x2: 8.0-4.1= 3.9
Trial 3:
1x1: 1.0-0.3=0.7
1.5x1.5: 3.4-2.2= 1.2
2x2: 8.0-4.1= 3.9
All 3 trials shows that the bigger the surface area the cube has, the more molecules
diffuses into the cube within the same amount of time.
Conclusion:
The hypothesis stated earlier had been accepted through this experiment. Through the
analysis, calculation that shows the more the surface area a cell have, the more
efficient diffusion is going to be. The 2x2x2 cube is to represent the bigger cells that
appear in nature and the experiment had proven the hypothesis correct.
Evaluation:
If this lab were to be repeated, the first change would be the measuring tool and the
equipment used to measure and cut the agar cubes. Errors were made during the
Benson Cheng
4A Bio Linzel
Grant Proposal
process of measuring the agar cubes. The 30 cm ruler did not provide an accurate
enough measurement. Many errors occurred during the process of cutting the agar
into little cubes, although the scalping progress had been carefully carried out, human
errors are unavoidable element of an experiment.