Question

What protein that is present on the outer membrane of Gram negatives allow molecules in based on size?

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Answer 1

Porins are beta barrel proteins that cross a cellular membrane and act as a pore, through which molecules can diffuse.

Unlike other membrane transport proteins, porins are large enough to allow passive diffusion, i.e., they act as channels that are specific to different types of molecules. They are present in the outer membrane of gram-negative bacteria.

Porins are primarily involved in passively transporting hydrophilic molecules of various sizes and charges across the membrane. Generally, only substances less than 600 Daltons in size can diffuse through.