Surface Area to Volume Ratio and the Relation to the Rate of Diffusion.

Cells and molecules in the environment are constantly moving and changing, for cells to function properly there is a need for equilibrium to be met. The size of the cell and the solution outside of the cell affects the rate of diffusion and osmosis in the cell. Cells are constantly trying to reach an equilibrium with the molecules and substances around it, which is why there are such terms as: hypertonic, hypotonic and isotonic. The procedures allowed testing of whether or not surface area or volume increased diffusion and how different substance control diffusion. Cells are constantly moving to reach equilibrium through diffusion and osmosis.

The experiment of the lab was to demonstrate knowledge of the concepts of diffusion and osmosis. Diffusion is the movement of substances moving from a high concentration to a low concentration. For this lab the rate of osmosis was measured in concentration. The concentration stayed the same and increased through the experiment. At the beginning of the experiment the sacs were weighed to determine the tonicity of water throughout the experiment. Timing was also a factor each 15, 30, 45 minute interval the sacs were weighed and recorded. Each sac had a different amount of solution in them. The tonicity of the sacs was determined as well by the final weights and the final percent of gain or loss of water in the sacs.

Two variables that affect the rate of diffusion are the MWCO membrane and the solute concentration. Increasing the membrane size and solute concentration will also increase the average diffusion rate. Decreasing the membrane size and solute concentration will reduce diffusion rates and can even prevent all diffusion.

The experiment proved my hypothesis correct that as the size of the Agar cube grows larger; the diffusion rate will be slower therefore taking up more time. The cubes were put into hydrochloric acid and left by, in order to exchange materials through diffusion, as a sample of cells in real life. As we can see the cube with the largest surface area and volume has the smallest surface area to volume ratio. If the surface area to volume ratio gets too small, then the substances won’t be able to enter the cell fast enough to fuel the reactions, because the surface area controls the rate of the exchange of materials while as the volume grows larger it will need more materials to enter and exit, in a more quicker rate, therefore waste products will start to accumulate within the cell as they will be produced faster than they can be excreted. In addition, the cells will not be able to lose heat fast enough and so may overheat. This was concluded from the experiment, where as the Agar cube dimension were larger, the rate of diffusion was much smaller from the Agar cube with the smaller dimension, where the last had a larger V: SA ratio than the larger cube.

7. Explain how incubation plant tissues in a series of dilutions of sucrose can give an

1. Understand the importance of diffusion to cellular metabolism and the how it constraints the evolution of cell/body size and shape

1. The relationship between rate of diffusion/ osmosis, volume, and surface area can be easily seen and analyzed through the data that was collected from procedure one: Surface Area and Cell Size. Phenolphthalein is a dye-material in this lab that was used to determine whether a substance was an acid or base. This could be told as the phenolphthalein changed into a murky. Muddled and clouded color when mixed with acids. When the chemical aid was mixed in with a base, the color

▪ Surface area to volume ratios and the ability of cells to get nutrients in and waste products out of the cell

The objective of this experiment is to develop an understanding of the molecular basis of diffusion and osmosis and its physiological importance. Students will analyze how solute size and concentration affect diffusion across semi-permeable membranes and how these processes affect water potential. Students will also calculate water potential of plant cells.

The following hypothesis was made in regard to effect of the concentration gradient on the rate of diffusion: The higher the concentration gradient, the faster the rate of diffusion.

Diffusion is the movement of molecules from a region of higher concentration to a region of lower concentration. The rate at which molecules diffuse can be determined by the relationship of molecular weight and that rate of diffusion through a membrane. Hypothesis of this experiment is that the fluid with higher molecular weight will diffuse at a slower rate and distance.

In conclusion, the potato cube with the highest surface area to volume ratio (the 1x1x1 cube) had the fastest rate of diffusion as it had the largest percentage increase in mass. While all the other cubes of potato had larger increases in mass at face value compared to the smallest cube, the smallest cube had the largest overall gain in percentage. The results support my hypothesis that the smallest cube will have a higher rate of osmosis because it has a proportionally larger amount of surface area compared to its volume.

Diffusion is the transfer of molecules from an area that has a higher concentration to an area that has a lower concentration. Osmosis is the diffusion of water. The purpose of this experiment was to study the process of osmosis. In order to test osmosis, eggs that had been soaking in vinegar were taken and placed in four beakers of solution with different levels of glucose. Using this experiment we were able to determine the rate of osmosis of different solutions, with various amounts of glucose, through eggs. In the results of this lab it was found that the eggs were either hypertonic or hypotonic and that the

This experiment was used to examine the hypothesis that: Osmosis is dependent on the concentrations of the substances involved.

Passive diffusion, also known as simple diffusion, is used to describe the exergonic reaction of a substance where the substance passes in the direction of the concentration gradient. Most of the molecules move from the area of high concentration, inside the membrane of a cell, to the outside where there is