Where do dag and ip3 originate?
they are formed by phosphorylation of camp.
they are ligands expressed by signaling cells.
they are hormones that diffuse through the plasma membrane to stimulate protein production.
they are the cleavage products of the inositol phospholipid, pip2.

Option (4).

Explanation:

Phosphatidylinositol4,5-bisphosphate (PIP2) is the phospholipid present in plasma membrane. This lipid is important for the cell communication and cell signalling process.

The PIP2 can cleave and give two main products are DAG (diacylglycerol) and IP3 ( inositol 1,4,5-trisphosphate). These two molecules are important for the cell signalling.

Thus, the correct answer is option (4).

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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