[Campbell Biology P.893] Based on Figure 39.4 and the accompanying text, which statement cor... | Practice Question

Based on Figure 39.4 and the accompanying text, which statement correctly describes the second messenger pathways activated by phytochrome during de-etiolation?

  • A: Both cGMP and Ca2+ activate the same protein kinase, leading to gene expression.
  • B: The activation of phytochrome directly leads to a decrease in cytosolic Ca2+ levels.
  • C: cGMP acts as a second messenger that activates a protein kinase, while increased cytosolic Ca2+ activates a different protein kinase.
  • D: Second messengers are small molecules that transfer the signal from the nucleus to the cytoplasm.

Explanation

The 'Transduction' section and Figure 39.4 clearly describe two distinct pathways involving second messengers. One pathway uses cGMP, which activates 'Specific protein kinase 1'. The other pathway involves an increase in cytosolic Ca2+, which activates 'Specific protein kinase 2'. Both pathways eventually lead to gene expression for de-etiolation proteins.