115. Which of the following best describes the conditions expected after 24 hours? (A) The bag will contain more water than it did in the original condition. (B) The contents of the bag will have the same osmotic concentration as the surrounding solution. (C) Water potential in the bag will be greater than water potential in the surrounding solution. (D) Starch molecules will continue to pass through the bag. (E) A glucose test on the solution in the bag will be negative.

116. If, instead of the bag, a potato slice were placed in a beaker of distilled water, which of the following would be true of the potato slice? (A) It would gain mass. (B) It would neither gain nor lose mass. (C) It would absorb solutes from the surrounding liquid. (D) It would lose water until water potential inside the cells is equal to zero. (E) The cells of the potato would increase their metabolic activity.

Essay: Communication occurs among cells in a multicellular organism. Choose THREE of the following examples of cell-to-cell communication, and for each example, describe the communication that occurs and the types of responses that result from the communication.

  • Communication between two plant cells.

  • Communication between two immune cells.

  • Communication either between a neuron and another neuron, or between a neuron and a muscle cell.

  • Communication between a specific endocrine-gland cell and its target cell.

Examples—IB questions related to cell membranes:

[November 1999 Paper One (multiple choice), #2]:

2. The cells of plant roots can take up ions from the soil against the concentration gradient. What is the process used? (A) Osmosis. (B) Passive transport. (C) Diffusion. (E) Carrier-assisted transport.

[November 1999 Paper Two]:

Part A (Extended Response) #2 A. Draw the structure of a nephron. B. Identify where most active transport occurs and identify one specific location where active transport occurs in plants. C. Define water potential. D. Explain the process of water uptake in roots by osmosis. E. List three abiotic factors which affect the rate of transpiration in a typical terrestrial mesophytic plant.

Part B (Extended Response) A. List three functions of lipids. B. Outline the production of ATP by chemiosmosis in the mitrochondrion. C. Explain the process of muscle contraction.

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