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Exercise 4: Cell Transport

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Micol Picornell

on 21 April 2014

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Transcript of Exercise 4: Cell Transport

Exercise 4: Cell Transport
Rate of diffusion of potassium permanganate: 0.012 cm/min

Rate of diffusion of methylene blue:
0.0056 cm/min

Rate of diffusion of congo red:
0.0033 cm/min
- process by which molecules move from high concentration to lower concentration
A. Diffusion in water
1. Get two test tubes. Half-fill the first one with tap water and the other test tube with distilled water. Label each accordingly.
B. Diffusion in Colloid
1. In three test tubes filled with hardened 5% gelatin solution, add 1 ml of each of the following reagents in separate tubes - potassium permanganate, methylene blue and congo red.
Parts A & B
- equal dispersion of solute throughout the system
- on the dividing line between solutions and heterogeneous mixtures
2. Using forceps, drop at least two crystals of potassium permanganate in each test tube.
3. Place the test tubes on a rack and make sure they are not disturbed by movement.
4. Observe and record the time when the color has completely dispersed - indicated by dispersion of a purplish, light color - in the water in both test tubes.
Left: distilled water
Right: tap water
The potassium permanganate diffused faster in the distilled water.
2. At five minute intervals, record the distance traveled by each stain through the gelatin. Do this for 90 minutes.
Potassium permanganate diffused faster in colloid, followed by methylene blue then congo red.
Factors affecting diffusion:
Concentration gradient
Surface Area
Molecular weight
Presence of other molecules
How does diffusion in gelatin compare with diffusion in water?
Diffusion would occur faster in water. This is because its liquid state allows for more collisions, spreading particles more effectively.
On the other hand, particles move slower in the solid state of gelatin, significantly slowing down diffusion.
Congo Red
Meth. Blue
The potassium permanganate diffused slower in the tap water. Although the solvents were both in liquid state, tap water contains other molecules from impurities, which can impede diffusion.

Distilled water, on the other hand, does not contain impurities which means there would be hindrance to diffusion.
Seleena Lim, Micol Picornell, Michael Siao, Yumi Tokoyo
KMnO4 - 158.03
Methylene Blue - 319.85
Congo Red - 696.66
Molecular Weight
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