POST-LAB ASSIGNMENT: DIFFUSION Observation: Table 1: Calculating the Surface Area to Volume Ratio of a Cube Object Shape Side Length of cube Units - mm Surface area of the object Units? Volume of the object Units? Surface area to volume ratio of the object 1 cube 7 2 cube 10 3 cube 15 4 cube 20 Graph 1: Graph the surface area/volume ratio versus the size of the cubes (i

Question

POST-LAB ASSIGNMENT: DIFFUSION

Observation:

Table 1: Calculating the Surface Area to Volume Ratio of a Cube

Object	Shape	Side Length of cube Units - mm	Surface area of the object Units?	Volume of the object Units?	Surface area to volume ratio of the object
1	cube	7
2	cube	10
3	cube	15
4	cube	20

Graph 1: Graph the surface area/volume ratio versus the size of the cubes (i.e. side length of cube) using the graph below. Remember to use TAILS.

Question: How will diffusion be affected by differences in surface area to volume ratio?

Hypothesis:

Prediction:

Experiment:

Independent and dependent variables

Control and experimental groups

Procedure: A list of steps briefly describing the procedure.

Analyze Results:

Table 2: Amount of time for diffusion to occur in different sizes of agar cubes. Data from an actual lab has been provided for you.

Side Length of cube (mm)	Surface Area /Volume Ratio	Time-Trial 1 (min)	Time-Trial 2 (min)	Time-Trial 3 (min)	Average Time (min)
7	3.5	4.8	5.1	5.2	5.03
10	5	11.3	11.5	10.8	11.2
15	7.5	16.2	16.4	15.9	16.2
20	10	52	48	51	50.3

Graph 2: Use “TAILS” to construct a graph showing the relationship between surface area to volume ratio and average amount of time it takes for diffusion to occur in the agar blocks.

Summary of Results:

The graph of Average time to diffuse was plotted against the surface to volume ratio of the cube. The average time appear to increase with the decrease in surface to volume ratio.

Conclusions: Use CER format

Thinking about Diffusion and Cell Shape:

Why do you think cells would evolve to have a certain size? How does cell size help speed up or slow down diffusion across the plasma membrane and through the cytoplasm of a cell?

Cell size will determine the surface area to volume ratio .If the surface area to volume ratio is more than diffusion of substance will be much faster, if volume is more and surface area is less then diffusion will be slow and less.

Why do you think cells would evolve to have a certain shape? Think about the cells that you looked at earlier with shapes other than a sphere or cube. How do you think a shape other than spherical or cuboidal could help speed up diffusion across the plasma membrane?

shape of cells is modified for function of cells, cell shape if the cell is having a shape like a rod shape as in E. coli or spiral shape or comma shaped as in vibrio member here to large surface area will increase the rate of diffusion.

Mature red blood cells (RBCs) do not have a nucleus, which changes its shape from spherical to a donut-like shape. Explain how the loss of the nucleus in a mature RBC would affect its surface area to volume ratio and how you think this would be important for diffusion of oxygen that occurs into and out of the RBC.

In RBC the presence of nucleus increases the volume of the cell so when volume is more compared to Surface area then the diffusion of oxygen might decrease. So loss of nucleus will make the cell volume less and increase its surface area.

To calculate a rate, divide the change in the amount of something (e.g. mass or distance) by the change in time:

7mm

Change in amount

Change in time

7 mm Rate =

3.5 mm

Calculate the rate of diffusion for each cube in Table 2, using the average time. [Hint: How far does the acid diffuse?]

Rate of Diffusion in Cubes of Different Size

Side Length of Cube (mm)	Distance Acid Diffused (mm)	Average Time of Diffusion (min)	Rate of Diffusion (mm/min)
7	3.5	5.03	0.695
10	5	11.2	0.446
15	7.5	16.2	0.4629
20	10	50.3	0.1988