Definition: This is a type of protein found in the cell membrane, which regulates the coming and going of substances into or out of the cell. Example: Like little doors, , open and close to allow substances into or out of a cell.

membrane proteins

Explanation:

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option a is correct i.e.

explanation:

in context to the membrane of nerve impulse, the outer membrane of neuron is semi permeable that is only sodium ions can pass through the membrane i.e. smaller ions can pass through the membrane while larger ions cannot pass through it.

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explanation:

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