Please help me answer these. I am practising for an exam and am not sure of the answers for these questions.

A cell is placed into a solution that has the same osmolarity. However, one
of the ions in the solution is able to move across the membrane (the cell
does not contain this ion). After a period of time, the solution into which
the cell was placed would become: (1 mark)
a) hyperosmotic
b) hypotonic
c) isotonic
d) hypertonic
e) iso-osmotic

Is it iso-osmotic?

Which of the following molecules is least likely to cross the plasma
membrane? (1 mark)
a) Steroids
b) Fatty acid
c) Oxygen
d) Disaccharide <<<< This one because it’s so large?
e) Water

The use of probenacid, an organic acid-based drug, in the treatment of gout takes
advantage of which of the following properties to achieve its effects?
a. Competition
b. Specificity
c. Passive diffusion along a concentration gradient <<<< This one?
d. Saturation
e. Fick’s Law.

Also, is Extracellular fluid?
a) dilute salt soltn surrounding cell
b)another name for interstitial fluid

Analysis of the cells in the intestine reveal that they are permeable to water,
whereas some cells in the kidney tubule are not permeable to water at all. Can you
suggest two reasons why these two types of cells might be different (structurally) to
each other?
Is this about channel proteins and amount of lipid?