. In the following diagram of an amino acid, what does R stand for?

It marks the spot where two amino acids will bond.
It is a glucose molecule.
It is a group of elements that is different for different amino acids.
It is a triglyceride group that will help create a bond for the amino acid.

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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not sure if this is what you'r looking for eubacteria and archaebacteria

the answer is cell division : )

the cost of mining is extremely low compared to the money earned from mining, creating income to improve the environment.