Question

Which substance would have normally have the least difficulty crossing a cell membrane?

Answer 1

 There is a small difference between the difficulty of substances to cross a cell membrane since the diffusion of substances through cell membranes always occurs going down by gradients of concentration. It does not require an energy expenditure (ATP).Plasma membranes have selective permeability. Different molecules move in different regions and at different speeds. A concentration gradient directs the three types of passive transport: simple diffusion, facilitated diffusion and osmosis.

Answer 2

The charged molecules or ions have the least difficulty crossing a cell membrane.

What is a cell membrane?

Cell membrane also known as plasma membrane or cytoplasmic membrane is the membrane around the cell.

The cell protect the cell from outer environment.

It also protects the cell from invaders and harmful elements and ions.

The cell membrane allows non-charged elements and small ions to pass through it.

It does not allow non-polar and charged molecules to pass through it.

Thus, the charged molecules and bigger ions does not pass through the cell membrane.

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