TWIS Post #2: Diffusion

   Last weeks lab was about a 8. I've done this before so I already knew what was going to happen, there was no surprise but it was still cool lab. It wasn't challenging for me. I passed the test that we took but I didn't finish the written part of the lab because I missed a day.

   We created a "cell" using dialysis tubing, string, starch indicator, starch, glucose, and water. To make the cell we had to soak the dialysis tubing in water to open in then tie one end with the string so there is no leakage. Then we filled the dialysis tubing with starch and glucose then tied the other end of the cell. Then put it in a cup filled with water and added starch indicator to the water outside of the cell. The cell I made changed color very quickly but you can see the starch inside of the cell turn into a dark purple almost black. This shows that the iodine from the starch indicator entered the cell.

   While the iodine was entering the cell glucose was leaving the cell to create equilibrium. We took a pipet full of the solution around the "cell" and glucose indicator and put it in a test tube. Then we put the test tube in a hot water bath. The liquid inside of the test tube turned orange which shows that the glucose from inside of the cell diffused out of the cell and into the liquid around it. Since the "cell membrane" of the cell we created is selectively permeable only small molecules can enter and exit the cell that is why only iodine and glucose diffused. The starch cannot move in or out the cell because the molecules are too big to diffuse out of the cell.

   Active transport is the movement of molecules from low concentration to high concentration. This requires ATP (energy). Imagine you are late for work or school and you have to take the bus and the bus is PACKED. You trying to squeeze into the bus requires energy. That is active transport. 

Molecule B is entering the cell through diffusion. There are four of molecule B outside of the cell and one inside. The molecules are moving from low concentration to high concentration therefore it is diffusion. Molecule A has four on the inside and one on the outside. Since it is moving from low concentration to high concentration therefore it is active transport.