Cell Transport

Alba, Maxine Lally T. Bries, Edmond

Cu, Joanna Pauline E. Cruz, Wendell Cell Transport: Diffusion in Colloidal Medium  Abstract 

Diffusion is an important biological process in which materials move from an area of high concentration to low concentration. One factor that affects the rate of diffusion is the size of  diffusing particle. In this experiment, three different stains were tested for their speed of diffusion through a colloid. The test stains were potassium po tassium permanganate, methylene methylene blue, and congo red while the diffusing medium was 5% gelatin solution. Potassium permanganate was found to be the fastest to diffuse through the gelatin followed methylene blue and congo red respectively.

environmental conditions. In so doing, this

Introduction

experiment shall compare the diffusion speed Diffusion refers to the movement of  materials across the concentration gradient.

of three different stains of different molecular weight through a colloidal medium.

At a molecular level, diffusion results from the random motion of particles due to their

Methodology

kinetic energy. energy. The goal of the diffusion is to create equilibrium in the concentration of  materials in the environment.

hardened 5% gelatin solution. One mL of potassium permanganate, methylene

One of the uses of diffusion is in the maintenance of a cell’ s

Three tests tubes were filled with

internal environment.

The cell needs to regulate its concentration of  materials for chemical reactions to occur which in turn sustains life. Thus, it is important to know how materials move

blue, and congo red were added to three separate tubes of gelatin solution. The setup was then observed. The distance travelled by each stain through the gelatin

was

measured

every

minutes for one and a half hour.

through a medium and what factors affect  diffusion. The speed of diffusion is determined by temperature, size of the diffusing particle, and viscosity of the environment. The size of  diffusing particle is inversely proportional to the

speed

of

diffusion

given

similar

KMnO4

Methylene Blue

Congo Red

five

55 60 65

Results and Discussions KMnO4 Methylene Blue Congo Red

Ta

7.4 7.5 7.6

1.1 1.1 1.1

0.9 0.9 0.9

Table 1 shows the distance travelled by the different stains through the gelatin recorded every five minutes.

Potassium

permanganate

exhibited the fastest diffusion speed Potassium permanganate travelled the fastest through the gelatin. After five minutes, the potassium permanganate stain had already travelled significantly through the gelatin at 3.6 cm while the other two had barely travelled with only

because it has the smallest particle size among the three test stains. Potassium permanganate,

five minutes, the potassium permanganate had already reached the bottom of the tube while methylene blue and congo red reached down only 1.1 cm and 0.9 cm from

blue,

and

congo red have the following molecular weights respectively: 158 g/mol, 320 g/mol, 697 g/mol. Given that the molecules have the

0.7 cm and 0.6 cm for methylene blue and congo red, respectively. After an hour and

methylene

same amount of kinetic energy and the same

environmental

same

temperature

conditions and

(the

diffusing

medium), small molecules move faster and large molecules. This factor affecting diffusion is more pronounced in materials

the top of the gelatin, respectively.

diffusing through a colloid, such as the gelatin used in the experiment since a Time (min) 5 10 15 20 25 30 35 40 45 50

Distance Traveled (cm) KMnO4

3.6 4.5 4.8 5.3 5.6 6.0 6.4 6.45 6.7 7.0

Methylene blue Congo red

0.7 0.9 0.9 0.95 0.95 0.95 1.0 1.05 1.1 1.1

0.6 0.7 0.7 0.8 0.8 0.8 0.8 0.85 0.85 0.9

semi-solid substance has considerably large particles that can act as barriers in the movement of particles. In so doing, smaller molecules have the advantage because they can slip through the gaps more easily than large molecules.

Conclusion

The speed at which particles travel through a medium is inversely proportional to both atomic weight and particle size. This thus affects the rate of diffusion, with small particles, of less weight being able to diffuse faster in a given medium compared to larger particles, of greater weight given the same conditions.

References Hyper Physics. n.d. Georgia State University. November 27, 2012. http://hyperphysics.phyastr.gsu.edu/hbase/kinetic/diffus.html Reiner J. Diffusion in colloidal media. Bulletin of Mathematical Biophysics. 1, 143-187 (1939) PhysioWeb. n.d. University of Vermont. November 27, 2012. http://physioweb.uvm.edu/diffusion/ FrapPages1.htm