Which of the following consists of an amino group, a carboxyl group, and a
side chain?
o
a. a carbohydrate
o
b. a nucleotide
o c. dna
o d. an amino acid

D). An amino acid

Explanation: All Amino acids have a carboxyl group (COOH), an amino acid group (NH2) and a side chain. The side chain is what distinguishes one amino acid from another. Some side chains are polar, hydrophobic, non polar and aromatic in nature. The carboxyl group is what classifies them as acids while the amino group (amine) is what gives them the name "amino".

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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here is the answer

water, ice, acids, salts, plants, animals, and changes in temperature are all agents of weathering. weathering is the breaking down or dissolving of rocks and minerals on earths surface. once a rock has been broken down, a process called erosion transports the bits of rock and minerals away.