Which of the following substances do animal cells contain? chitin cartilage cellulose collagen

Collagen  is a substance contained by animal cells.

Explanation:

An exclusive substance of animal cell, the collagen is constructed by amino acids like- Proline, glycine, arginine etc. It is present in the connective tissues and flesh of animals. It can be locate in the skin tissue that is connective and gives it elasticity and renews it constantly.

It has major portion of body proteins in it and it helps in strengthening the structure of body and skin. It can also be seen in the tissues of muscle, in the vessels of blood, kidney etc. It keeps the tissues and cells bound together.

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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