Question

when ctx is present in the intestinal cell, the effect on pka is that it deactivates camp. it is more abundant in the cells. it can no longer phosphorylate cftr. it phosphorylates proteins that it could not influence before ctx was present. it can no longer phosphorylate g - proteins.

Explanation:

When CTX (cholera - toxin) is present in intestinal cells, it activates adenylate cyclase, leading to an increase in cAMP levels. The elevated cAMP activates Protein Kinase A (PKA). Activated PKA then phosphorylates proteins that it could not influence before CTX was present, which disrupts normal cellular functions. PKA does not deactivate cAMP. Its abundance in cells is not directly affected by CTX in terms of synthesis - degradation balance. PKA can still phosphorylate CFTR and g - proteins under normal conditions related to CTX action.

Answer:

it phosphorylates proteins that it could not influence before CTX was present.