Relationship of time and rate diffusion

Understanding diffusion The key parameter in this equation is the diffusion constant, D, with larger diffusion constants indicating a higher rate of jiggling around. The value of D is. A bigger volume agar jelly would have a lower SA:V, so would the rate of diffusion be the same for all jelly of different sizes or would it be slower for a jelly with a. where R is the rate of diffusion in mol/s and M is the molar mass in g/mol. J is the flux, or movement, of the molecules in a given time interval denoted by units of moles/(time×area); D is the Using the following relationship.

At the same manner, the agar-water gel test is used to assess and verify the same matter. This study aimed to determine the effect of molecular weight and time on the rate of diffusion of substances via the glass tube test and agar-water gel test.

The specific objectives were 1. For the first set up, two feet glass tube was fastened horizontally to a ring strand, as shown in Figure 1. Using fine forceps, two cotton balls of the same size were moistened, one with Figure 1. One end of the tube was then plug with one wet cotton ball and the other end with the other cotton ball. After some time, a white smoke appeared. The distance of the white smoke to each of the cotton balls was obtained by measuring its length, comparing each measurement and then getting the total distance and average ratio of the diffusion of the substances.

A graph comparing the distance of the substances with that of the white smoke was then plotted and analyzed. For the next set up, a petri dish of agar-water gel with three wells was obtained. The three wells were labeled as follows: Each well was placed with one drop of the prepared solution of each substance.

The petri dish was then immediately covered and the diameter in mm. At a regular five-minute interval for thirty minutes, the diameter of the colored area of each substance was measured and recorded, as shown in Figure 3.

Graham's law - Wikipedia

A graph comparing the distance of each interval to its original position was also plotted and analyzed. The position of the substances at zero minute. The position of the substances after 30 minutes. Computing for the ratio of the substances by simply getting the proportion of NH 3 and HCl, the average ratio would be 1.

This implies that NH3 have diffused faster than HCl. Since the gaseous molecules of NH3 diffused at a faster rate, it reached the opposite side of the glass tube reacting with HCl wherein the white smoke formed.

The value of D is microscopically governed by the velocity of the molecule and the mean time between collisions. This rule of thumb shows that the diffusion time increases quadratically with the distance, with major implications for processes in cell biology as we now discuss. The decrease in the diffusion constant in the cytoplasm with respect to water as molecular weight increases.

Diffusion  useful equations

For the different proteins marked in green see Kumar et al and entries in the compilation table below. How long does it take macromolecules to traverse a given cell? We will perform a crude estimate. Using the simple rule of thumb introduced above, we find as shown in Figure 2 that it takes roughly 0. An axon 1 cm long is about times longer still and from the diffusion time scaling as the square of the distance it would take seconds or about two weeks for a molecule to travel this distance solely by diffusion.

This enormous increase in diffusive time scales as cells approach macroscopic sizes demonstrates the necessity of mechanisms other than diffusion for molecules to travel these long distances. For extremely long neurons, that can reach a meter in length in a human or 5 meters in a girafferecent research raises the speculation that neighboring glia cells alleviate much of the diffusional time limits by exporting cell material to the neuron periphery from their nearby position K.

This can decrease the time for transport by orders of magnitude but also requires dealing with transport across the cell membrane.

Fluorescence recovery after photobleaching in bacteria. The laser photobleaches the fluorescent proteins in a selected region.

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Because of diffusion, proteins that were not bleached come into the bleached region over time. B Higher resolution schematic of the photobleaching process over a selected region within the cell. The left hand screen slider lets you control the vScope's magnification. The right-hand slider controls the temperature of the system. The graph zoom in button expands the graph that displays the average distance the set of particles have moved from their original position. Open the vScope and see if you can get the buttons to work — what happens if you set the temperature to "0"? What is the maximum temperature that the vScope can reach?

You will use the vScope to study a two basic properties of diffusion. These are the relationship between time and the average distance the particles have traveled. To answer these question you need reliable data. These numbers will be part of your lab report! Perform at least three independent experiments using the vScope.

Graham's law

Each experiment should be at least 30 seconds long. The simplest approach is to let the experiment run for about 33 second; stop it and then determine distance traveled at various time points e. Make a table of your data.