Nonpolar and lipid-soluble.
In general, any nonpolar substance has this ability to pass through the bilayer. However, with membrane transport proteins, active or passive transport allows all sort of molecules into cells, anything polar. Rating Newest Oldest. Best Answer: Since the lipid bilayer of cells is nonpolar, only non-polar substances can pass directly through the bilayer without the need for any help by membrane transport proteins. For example, all steroids are non With regard to molecules, the cell membrane is very permeable to water, certain lipid-soluble substances, amino acids, and sugars, but relatively impermeable to large molecules such as proteins and polysaccharides. Ask a question. We’ve answered 397,663 questions. We can answer yours, too.  The lipid bilayer is a thin polar membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around all cells. Biological membranes typically include several types of molecules other than phospholipids. A particularly important example in animal cells is cholesterol, which helps strengthen the bilayer and decrease its permeability. Biology I Chapter 5 Membranes LearnSmart 1. The lipid bilayer of cell membranes acts as a barrier to the free movement of substances that are o Hydrophilic o Water soluble 2. True or False: In order to survive, grow and reproduce, a cell must continually exchange materials and information with its environment. o True 3 The most important property of the cell membrane is its selective permeability: some substances can pass through it freely, but others cannot. Small and nonpolar (hydrophobic) molecules can freely pass through the membrane, but charged ions and large molecules such as proteins and sugars are barred passage. The selective permeability of the cell membrane allows a cell to maintain its internal composition at necessary levels. Nonpolar and small polar molecules can pass through the cell membrane, so they diffuse across it in response to concentration gradients. Carbon dioxide and oxygen are two molecules that undergo this simple diffusion through the membrane. The simple diffusion of water is known as osmosis. Small and nonpolar (hydrophobic) molecules can freely pass through the membrane, but charged ions and large molecules such as proteins and sugars are barred passage. The selective permeability of the cell membrane allows a cell to maintain its internal composition at necessary levels.
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what types of substances can diffuse through the lipid bilayer