Molecules such as glucose and amino acids are not lipid soluble and therefore they
A) easily pass across the cell membrane.
B) require active transport to cross the cell membrane.
C) must be converted to lipids before they can enter a cell.
D) combine with carrier proteins and pass across the cell membrane by facilitated transport.
E) must be engulfed by a cell using endocytosis.

Question

Quizplus · Accepted Answer

Molecules that are not lipid soluble cannot easily pass through the cell membrane on their own. Instead, they require the assistance of carrier proteins to pass through via facilitated transport. This is a type of passive transport where the molecule moves down its concentration gradient (from high to low concentration), but requires the help of the carrier protein to make it through the hydrophobic interior of the membrane. Active transport, which requires the use of energy to move a molecule against its concentration gradient, is not typically used for molecules like glucose and amino acids. Lipid conversion and endocytosis are also not necessary for these types of molecules to enter a cell.

Molecules Such as Glucose and Amino Acids Are Not Lipid