Question

Some solutes are able to pass directly through the lipid bilayer of a plasma membrane, whereas other solutes require a transport protein or other mechanism to cross between the inside and the outside of a cell. The fact that the plasma membrane is permeable to some solutes but not others is what is referred to as selective permeability. Which of the following molecules can cross the lipid bilayer of a membrane directly, without a transport protein or other mechanism?
Select all that apply.a) proteinsb) waterc) ionsd) sucrosee) lipidsf) carbon dioxideg) oxygen

Answer 1

Answer:

Water

Oxygen

Carbon dioxide

Lipids

Explanation:

The plasma membrane is a lipid bilayer with a hydrophobic core made of nonpolar tails of phospholipids. The plasma membrane allows only uncharged, small and hydrophobic substances to pass through it. Charged particles such as ions, polar molecules such as sucrose can not cross the hydrophobic core of the plasma membrane.

Oxygen and carbon dioxide gases have small sizes and can diffuse through the spaces between the tails of phospholipids of lipid bilayer of the plasma membrane without any transport proteins. Lipids are hydrophobic and therefore, do not need any transport proteins to cross the lipid bilayer. The small water molecules are also free to move through the membrane.