A membrane that only "lets" certain molecules in while keeping other molecules out is called cell membrane.
Explanation:
A cell membrane is a semi-permeable membrane which acts as a barrier and a gatekeeper in that cell that allows some molecules to diffuse across while preventing others.Hydrophobic molecules that are small enough and gases pass across this membrane while larger molecules such as ions, sugar and amino acid are restricted to pass.Small polar molecules such as water also have there way past this membrane.
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Functions of a cell membrane : https://brainly.com/question/1269652
Keywords : cell membrane, molecules
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