# Investigating the relationship between diffusion and cell size

### How does surface area to volume ratio affect the rate of diffusion? | Socratic Biology Laboratory Investigation. Diffusion and Cell Size What does this graph show you about the relationship between surface area and volume? 4. A good. The efficiency of diffusion is determined by the size of a cell in particular its surface Our experiment investigated the relationship between surface area/ volume. In this activity, you will investigate, using model cells, the relationship between cell size and diffusion which will help to explain why cells remain small.

In this activity you will determine the extent and rate of diffusion of a substance into three cubes of different sizes. In addition, you will calculate the surface area to volume ratio for each cube. Materials — Each group should find the following at their lab table: No one should handle the agar blocks without gloves. All students should wash their hands after completing the lab. Take the measurements and draw scaled pictures of the agar blocks carefully and make sure you have all measurements required BEFORE doing the math. All measurements should be made to the nearest 0.

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You have a 3cm x 3cm x 6cm block of agar. Using the plastic knife, to carefully cut the block. Place the three cubes in the plastic cup. Add enough diffusion medium to cover all three cubes. Keep all cubes submerged for 10 minutes. As the cubes soak, use the following equations to complete Data Table 1. After 10 minutes, use the spoon to remove the agar cubes and carefully blot them dry on a paper towel. Then, cut the cubes in half, rinsing and drying the knife between each cut.

Using a metric ruler, measure the distance in centimeters that the diffusion medium diffused into each cube. Measurement C in the diagram below Record the data in Data table 2. We are making the assumption that C will be the same depth around the entire cube. Calculate the extent of diffusion into each cube as a percent of the total volume. Use the diagram to the right to help you. Rate of diffusion Cube size Time min.

## Diffusion and Cell Size

Explain why the diffusion of the diffusion medium into the agar cube caused the observed color change hint: Where have we seen these before? According to Data Table 3, which cube showed the highest extent of diffusion — the largest or smallest?

Cell Diffusion/Cell Size Activity - Summary

If each cube represented a living cell and the diffusion medium a substance needed within the cell, what problem might exist for the largest cell? Examine your data in Data Table 2 for a relationship between cube size and the rate of diffusion into the cube. Make a generalized statement about the relationship between the cell size and the rate of diffusion.

## Agar Cube Lab Report

Examine your data in Data Table 1. What does the length of a cube determines the efficiency of diffusion in cells? In this Experiment, I explored and investigated one of the most important cellular processes called diffusion. By measuring the distance of diffusion in agar cubes and transforming the data, I found results that explained what determined the efficiency of diffusion. The efficiency of diffusion is determined by the size of a cell in particular its surface area to volume ratio and was clearly reflected in my results and graphs. Put numerical results, conclusion and eval here. In this experiment, I explored and measured the efficiency of diffusion.

### Diffusion and Cell Size

Diffusion is one of the most important processes of a cell as it is used to transport materials such as molecules, nutrients, water, oxygen, and cellular waste through the cell membrane of a cell. In this experiment we used gelatin blocks called agar cubes to represent the cell, and measured how much distance Sodium Hydroxide could diffuse in the cube after a set time. Write something here about why cells are small — the theory about surface area to volume ratio Hypothesis: Therefore, materials in a cell that is smaller in size will diffuse much faster as the distance to the center of a cell that has a smaller volume and surface area is much shorter than larger cells that have corresponding larger surface areas and volumes.

The independent variable in this experiment is the length or size of the agar cubes. The dependent variable in this experiment is the amount distance of Sodium Hydroxide that diffuses into the agar cube.

Our controls were the total time in which the cubes were submerged in Sodium Hydroxide, the gelatin substance, and the materials used in conducting the experiments such as the scalpel, ruler, beaker, sodium hydroxide, phenolphthalein, gelatin etc. Distance NaOH diffused cm 0. Percentage of Diffusion In doing these calculations I successfully expanded and elaborated my raw data into data which could be graphed and further analyzed. The first graph shows that the length of the cube did not affect the distance diffused by the Sodium Hydroxide as expected.

As the length of the cube increased, the distance of diffusion by the Sodium Hydroxide stayed the same. The second graph shows that as the length of the cube increases, the percentage of diffusion decreases, showing a negative correlation.

This confirms that as the efficiency of diffusion decreases as the length of the cube decreases. The third graph shows that as the surface area to volume ratio increases so does the percentage of diffusion, showing a positive correlation.