Final answer:
The pathways activated by second messengers have characteristic features such as substrate specificity, sequential arrangement of proteins, and alterations in protein conformations achieved by phosphorylation and dephosphorylation.
Step-by-step explanation:
The characteristic of the pathways activated by second messengers include:
- Some pathway phosphatases and protein kinases have numerous proteins as their substrates; others act on only a single protein substrate or a single amino acid of a protein substrate. The activation or inactivation of proteins in signaling pathways is achieved by the addition or removal of phosphate groups by protein kinases and protein phosphatases, respectively. This modification can either affect the activity of enzymes or create binding sites for downstream components in the pathway.
- Each signaling pathway consists of a series of distinct proteins that operate in sequence. The proteins in the pathway interact with each other in a sequential manner to transmit the signal from the receptor to the target proteins, eventually leading to a cellular response.
- Alterations in signaling protein conformations are often accomplished by protein kinases and protein phosphatases that, respectively, add or remove phosphate groups from other proteins. Phosphorylation, catalyzed by protein kinases, changes the shape of proteins and can activate or inactivate them. Dephosphorylation, catalyzed by protein phosphatases, reverses the effect of phosphorylation.
Therefore, the correct answer is All of these answers are correct.