Living organisms constantly receive and interpret signals from their environment. Signals can come in the form of light, heat, water, odors, touch, or sound. Cells of multi-cellular organisms also receive signals from other cells, including signals for cell division and differentiation. The majority of cells in our bodies must constantly receive signals that keep them alive and functioning. All organisms also have signaling systems that warn of the presence of pathogens, leading to a protective response.

The key concept is that the many signaling systems of biology have very similar or related steps. The same signaling system can lead to very different responses in different cells or different organisms. Studies of the mechanisms of cell signaling are leading to new understanding of many diseases, and to new strategies for therapy.

Instructions: The following problems have multiple choice answers. Correct answers are reinforced with a brief explanation. Incorrect answers are linked to tutorials to help solve the problem.


1. Receptors

2. Signal responses I

3. Signal responses II

4. Kinds of signals

5. Bacterial cell signaling

6. Steroid hormones

7. Second messengers

8. Protein kinase cascades

9. G-proteins

10. Signaling events

11. Gap junctions

12. Cancer therapy

This resource is part of the Biology Links for One Laptop Per Child course which contains units on Exploring Life; The Cell; Genetics; Mechanisms of Evolution; The Evolutionary History of Biological Diversity; Plant Form and Function; Animal Form and Function; Ecology; and Astrobiology.

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