Question

1. What are the essential parts of a signaling pathway? 2. How could activating a transcription factor cause long-term cellular changes? 3. What roles can phosphorylation play in protein function? 4. What is the enzymatic activity of a kinase and of a phosphatase?

Answer 1

1. Components of a signaling pathway
i. Ligand
ii. Receptor
iii. Downstream signaling machinery
iv. Secondary messengers
v. Response factors

2. Activation of a gene's transcription would lead to the elevated levels of its gene product. So, it will perform its function at a greater rate. For example, if cellulose synthase transcription is activated, more amounts of cellulose synthase protein would be made. This would result in high cellulose production.

3. Posttranslational modifications can
i. Change the localization of the protein
ii. Inhibit a protein function
iii. Activate a protein function
iv. Increase/decrease stability
v. change interacting partners

4. Kinase adds a phosphate group to a protein. Phosphatase removes a phosphate group from a protein.