DO NOW How can muscle cells maintain (or keep) a high concentration of potassium inside the cell? If a cell increases or decreases in volume, what type of transport must happen? Building blocks of carbohydrates? Building blocks of proteins? Function of the nucleus?
Diffusion Through the Membrane State Lab
Selectively Permeable The cell membrane is selectively permeable because it only lets certain molecules pass through the membrane
Glucose, water, O 2, CO 2, amino acids, and other small molecules are permeable to the membrane Starch, proteins, and other LARGE molecules are NOT permeable to the membrane. – They must be DIGESTED, or broken down.
The state lab was all about DIFFUSION!!!!!! We used an “artificial cell” to observe the movement of glucose, starch, and starch indicator.
An indicator is used to test for the presence of a chemical substance. Starch indicator (iodine) is amber brown. It will turn blue/black in the presence of starch. The beaker was LEFT ALONE for 20 minutes
WHITE AMBER
An indicator is used to test for the presence of a chemical substance. Starch indicator (iodine) is amber brown. It will turn blue/black in the presence of starch. The beaker was LEFT ALONE for 20 minutes After 20 minutes, the bag turned black, the beaker stayed amber
WHITE AMBER BLACK AMBER
The bag turning black told us that starch indicator (iodine) moved into the cell. The water staying amber told us that starch DID NOT move out of the cell.
But what about glucose?....
In order to determine if glucose moved, a glucose indicator test had to be performed. Glucose indicator is clear blue, and IT MUST BE HEATED. Glucose indicator will turn red, yellow, or green (traffic light colors) if glucose is present.
A sample of the amber water was taken from the beaker and heated with glucose indicator. The test was POSITIVE. Glucose WAS present in the beaker.
I I I I I I I S S S S G G G G
I I I I I I I S S S S G G G G I I I I I S S S S S G G G G G G
Conclusion of the Lab Glucose and starch indicator were PERMEABLE to the dialysis tube membrane. Starch was NOT permeable to the membrane.