AP Biology Lab Class Results

October 31, 2003 – Happy Halloween!

Starch test in bag – diffusion (based on coloration from IKI indicator)

Glucose in bag (initial) – positive

Glucose in bag (final) – negative            *Final = after 30 minutes

Starch in bag (initial) – positive              in water: IKI

Starch in bag (final) – negative               in bag: starch and glucose

Explanation

Glucose went out of bag

IKI went into bag

Verification: coloration – solution in bag changed color; solution outside didn’t

            IKI much smaller than the starch (no live membrane, no active transport – based

            on diffusion/active transport alone)

Bag is porous – only certain things of certain sizes can pass through – no macromolecules

(starch), but micromolecule IKI can go through

Concentration gradients – all things go from high concentration to low concentration

-         no enhanced flow

-         increase temperature, Brownian movement increases – increases diffusion rate

-         decrease temperature, Brownian movement decreases – decreases diffusion rate

-         result of osmotic potential, not pressure potential à size of molecules ONLY

-         passive transport

                                                            Solution Color                         Test Tape Results

Changes in Dialysis Bag Mass

Table 1.4 – Average Data from Potato Lab