Enzymes are usually very specific as to which reactions they catalyze and the substrates that are involved in these reactions. The enzyme and the substrate possess specific complementary geometric shapes that fit exactly into one another. This is often referred to as "the lock and key" model.
I believe a valley or mountain, but I am not 100 percent sure.
Answer:
Letter a) Protists would have less permeable membranes than those in hypotonic or Isotonic environments, wlowing less water to enter the coll. Also, they could possibly develop higher salt concentration within the cell to retain water.
