Question

A study was conducted to understand the factors controlling the rate at

which molecules or ions travel across cell membranes. An artificial
membrane was created that was composed of a phospholipid bilayer only.
The speed at which various substances crossed this membrane was
measured. Some substances can pass through an actual cell membrane
much faster than they passed through the artificial membrane in this study
Which of the following statements best explains this finding?"
Actual cell membranes have a much thicker phospholipid bilayer than the artificial
membrane does
Actual cell membranes have a variety of proteins embedded in the membrane that are
absent in the artificial membrane
Hydrophobic substances spend more time between the two layers of phospholipid in
the artificial membrane than they do between the layers in an actual membrane
Hydrophilic substand spend more time attached to the polar region of the
phospholipids in the artificial membrane than they do attached to the polar region of
the phospholipid in an actual membrane

Answer 1

Proteins embedded in actual cell membranes facilitate the faster movement of substances compared to an artificial membrane that lacks these proteins.

Step-by-step explanation:

The speed at which substances cross a membrane can be influenced by factors such as the thickness of the phospholipid bilayer and the presence of proteins embedded in the membrane. In this study, the artificial membrane used had a phospholipid bilayer, but lacked the variety of proteins present in actual cell membranes. The proteins in cell membranes can facilitate the movement of substances across the membrane, allowing certain substances to pass through much faster than they would in an artificial membrane.

Therefore, the finding that some substances pass through an actual cell membrane faster than the artificial membrane can be explained by the presence of proteins embedded in the cell membrane that are absent in the artificial membrane.