# The relationship between cell size and diffusion lab questions

Diffusion is one of the very important processes by which substances such as nutrients, This activity will help you explore the relationship between diffusion and cell size by experimenting with model “cells.” In this experiment, you will use agar cubes to which the indicator Use this question to help formulate a hypothesis. In this lab, you will use cubes (representing cells) of agar that have an Calculate the surface area, volume, and surface area to volume ratio for each Answer the questions below – remember to be thorough, thoughtful, RSQ, and not lazy☺. Diagram: Results: We did the experiment twice, as to get a range of data, So generally, the relationship between the rate of diffusion and cell size is that the.

Interpretation In all the blocks of gelatin the rate of penetration of the hydrochloric acid from each side would have been the same but all the blocks take different amounts of time to clear because they are different sizes. As the blocks get bigger it takes longer for the hydrochloric acid to diffuse through all the block and so clear the dye. It takes longer to reach the centre of the cube even though the rate of diffusion is the same for all the cubes.

The larger blocks have a smaller proportion of surface area than the smaller blocks. The smallest block has 1. The largest block only has 0. This means that the hydrochloric acid is able to diffuse to the centre of the smallest block much faster than the largest block. The acid took 48 minutes to diffuse to the centre of the largest block but only 1 minute in the smallest block. A living cell would not survive if it had to wait 48 minutes for oxygen to diffuse through it so living cells need to be very small.

When the surface area to volume ratio goes down it takes longer for the hydrochloric acid to diffuse into the cube but if the ratio goes up then the hydrochloric acid diffuses more quickly into the block of gelatin. Some shapes have a larger surface area to volume ratio so the shape of the object can have an effect on the rate of diffusion.

It is important that cells have a large surface area to volume ratio so that they can get enough nutrients into the cell.

They can increase their surface area by flattening and becoming longer or by having a rough surface with lots of folds of cell membrane known as villi. The cell membrane is made up of a lipid bi-layer with many proteins integrated into it.

The concentration of oxygen in the cell is always lower than outside the cell which causes the oxygen to diffuse in. Gases will always dissolve from an area of high to low pressure.

The concentration of carbon dioxide outside the cell is lower than the concentration in the cell so the carbon dioxide will always dissolve out of the cell. Single celled organisms such as amoebas have a large surface area to volume ratio because they are so small.

They are able to get all the oxygen and nutrients they need by diffusion through the cell membrane. Larger organisms such as mammals have a relatively small surface area compared to their volume so they need special systems such as the lungs in order to get enough oxygen. Surface area to volume ratio is very important in lungs where a large amount of oxygen has to get into the lungs.

The lungs have a very large surface area because they contain millions of sacs called alveoli which allow oxygen to diffuse into the bloodstream. By having millions of these alveoli the lungs are able to cram a very large surface area into a small space.

## Investigating the relationship between cell size and rate of diffusion

This surface area is sufficient for all the oxygen we need to diffuse through it and to let the carbon dioxide out. It was bought at a chemical store and the package was labelled. The method of measuring the length of We use the same ruler for all cube edges This gives the experiment reliability. We already have a tray of agar with phenolphthalein.

The instructions are for one group. Cut as accurately as possible.

Using Agar Blocks for Diffusion - Biology Minute

Safety As NaOH is a corrosive acid that can cause chemical burns on skin and permanent blindness when contacted with eyes. Be sure to wear gloves all of the time and do not touch your eyes.

### Lab Report = Surface area to volume ratio effect on diffusion | Irena Sionek - relax-sakura.info

These are the used formulas and example operations. Calculating the surface area of cubes e — edge of the cube SA — surface area E.

Calculating the final volume fV — final volume w — edge of the little uncoloured cube in the centre of the whole agar cube e. It visibly differs from the data collected by other groups from which most are very similar. While data collected by the groups stays in the interval It is most probable that the reason of such an inconsistency is an incorrect conduct of the method. The time between taking out the cubes from the solution and measuring can impact the results.

Calculating the surface area to volume ratio and diffusion rate in each of the groups excluding group no. V — surface area to volume ratio e. V and the rate of diffusion. The experiment results seen on the graph trend line show that the bigger is the surface area to volume ratio, the bigger is the percentage volume of diffusion, so the rate of diffusion of pigment from the agar cube.

Looking at the data we can notice that smaller cubes of smaller volume have bigger SA: We can than state that the results of the experiment have also shown, that the smaller is the cube, the bigger is the rate of diffusion.

The graph appears to flatten off at the point of the cube with the dimensions 1,5cm x 1,5 cm x 1,5 cm and SA: The visible trend is called decelerating increase. The relationship between the variables has its explanation. The obtained results have a reflection in the biological world.

Cells need to take in nutrients from their surroundings and expel waste through their cell membrane. If there is a large surface area to volume ratio, there is more cellular membrane to take care of both of these functions. V gets smaller and there is not enough surface area to expel wastes or intake nutrients the cell has bigger volume so needs more of them fast enough and the cell shrinks or dies.

The first thing, which contributed to the low reliability of these experiment is a small, insufficient number of trials.

Second of all, it was already mentioned that the data collected by group number 6 is very different from the data collected by the other groups.