EVERYDAY SCIENCE

Detailed explanation-1: -Facilitated diffusion. Some molecules, such as carbon dioxide and oxygen, can diffuse across the plasma membrane directly, but others need help to cross its hydrophobic core. In facilitated diffusion, molecules diffuse across the plasma membrane with assistance from membrane proteins, such as channels and carriers.

Detailed explanation-2: -Explanation: Only small, uncharged molecules that are nonpolar can cross the cell membrane via diffusion.

Detailed explanation-3: -Gases like carbon dioxide and oxygen can move across the cell membrane via diffusion. Diffusion is the movement of gas molecules from a region of higher concentration, to a region of lower concentration through a semi-permeable membrane.

Detailed explanation-4: -Small nonpolar molecules, such as O2 and CO2, are soluble in the lipid bilayer and therefore can readily cross cell membranes. Small uncharged polar molecules, such as H2O, also can diffuse through membranes, but larger uncharged polar molecules, such as glucose, cannot.

Detailed explanation-5: -Small, nonpolar molecules (e.g. oxygen and carbon dioxide): These molecules can pass through the lipid bilayer and do so by squeezing through the phospholipid bilayers. They don’t need proteins for transport and can diffuse across quickly.