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1. Protein signals rely on signal transduction because the proteins themselves cannot pass through the cell membrane.
2. In order for the receptor to do its job, it needs to relay the signal into the interior of the cell. The protein does so by changing the shape of the inside portion of the receptor protein. If the receptor did not span the membrane, it could not do this.
3. c, a, d, b
4. The transduction step amplifies the message as soon as it enters the cell. This ensures that even a small signal (only a few signal molecules) is enough to elicit a huge response.
5. Reception, transduction, response.
6. When the receptor binds to the signal, the inside region of the receptor protein changes shape. This moves the message (but not the actual chemical signal) into the cell.
7. c, d, b, a
8. Neurons (the cells of the nervous system) use ligand-gated ion channels in order to transmit nerve impulses from one cell to the next.
9. Protein kinase enzymes play an important role in signal transduction because they amplify/increase the message by creating a phosphorylation cascade.
10. d. The yeast-mating signal pathway begins with the signal causing a protein kinase cascade, and that leads to the activation of specialized transcription factors. That in turn causes specific gene expression, which leads to directional growth of the yeast cell.