Answers to the Diffusion Review Question Sheet

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20.    Receptor molecules do not have anything to do with diffusion. They are involved in active transport.

21.    Receptor molecules. Neurotransmitters from one nerve cell interact with receptor molecules on the        next nerve cell to transfer the signal from one cell to the next.

22.    2 oxygen is used up in the cell maintaining a low oxygen concentration inside the cell. Conversely, carbon dioxide is produced inside the cell maintaining a higher concentration inside than outside. The arrows indicate flow from high concentrations to low concentration that is diffusion.

23.    the cell membrane controls what goes into and out of the cell.

24.    4  the paramecium uses energy to pump water out of the cell against the concentration gradient.

25.    distilled water is hypotonic compared to the cytoplasm of the blood cells hence, water flows from high conc. (outside of the cell) to low conc. (inside)

26.    3   The question states that the low water concentration is outside of the cell. water then leaves the cell causing it to shrink.

27.    4   only the concentration gradient directs diffusion.

28.    1   region A is more concentrated than region B

29.    2   This is the classic, text-book definition of cell respiration.

30.    A concentrated salt solution has a lower water concentration. The salt takes up some of the space where water could be.

31.    2   Count up the molecules inside compared to outside of the cell.

32.    The 2% salt solution can also be thought of as a 98% water solution (which is the same as the cytoplasm) Cells in isotonic solutions neither gain nor lose water.

33.    2   Distilled water is almost always hypotonic. the cell will get larger. The salt solution then provides a hypertonic solution for the cell and it will then shrink.

34.    3   In order to maintain a concentration gradient, the cell must use energy to bring calcium salts from the low conc. (outside) to the high conc. (inside).

35.    1   This is right from the lab we did. The Elodea cells lose water to the low water concentration environment.