Explain how diffusion limits the size of a cell.
9th grade level

Diffusion is powerful over a particular distance and bounds the size that a character cellular can gain.

Explanation: If cellular is an unmarried-celled microorganism, consisting of an amoeba, it is able to satisfy all of its nutrient and waste needs via diffusion. If the mobile is too massive, then diffusion is useless at finishing all of these responsibilities.

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation:

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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