AP BIOLOGY

Detailed explanation-1: -A selectively permeable membrane allows some types of molecules and ions to pass through, but not others. Starch does not pass through the synthetic selectively permeable membrane because starch molecules are too large to fit through the pores of the dialysis tubing.

Detailed explanation-2: -Consequently, larger uncharged polar molecules such as glucose are unable to cross the plasma membrane by passive diffusion, as are charged molecules of any size (including small ions such as H+, Na+, K+, and Cl-).

Detailed explanation-3: -Starch molecules are too large to pass through the membrane; however, the Iodine molecules are small enough. This results in a Starch-Iodine complex that is confined to where the Starch is trapped-ie, inside the “cell”.

Detailed explanation-4: -Proteins cannot passively diffuse across the cell membrane due to their size and polarity.

Detailed explanation-5: -Plant cells and diffusion The cell membrane is said to be partially permeable because only small molecules can pass through and larger molecules such as starch or proteins cannot. Diffusion is the movement of particles from a region of higher concentration to one of lower concentration.