Question

what types of molecules need more help to get through the cell membrane? What helps them get through?

Answer 1

Hydrophilic molecules struggle to cross the hydrophobic cell membrane and require transport proteins such as channel proteins and carrier proteins to facilitate their passage in a process known as facilitated diffusion. Active transport is also utilized when molecules need to be moved against their concentration gradient, requiring ATP for energy.

Step-by-step explanation:

Understanding the Cell Membrane and Molecule Transport

Hydrophilic molecules, which love water, have a hard time crossing the cell membrane due to its hydrophobic (water-hating) interior. To aid these molecules, the cell employs special structures called transport proteins. Transport proteins come in various forms, such as channel proteins and carrier proteins, and their main function is to assist hydrophilic molecules in passing through the membrane by a process named facilitated diffusion. Among these, there are also specific proteins like aquaporins that facilitate water transport. Ions and charged molecules also require transport proteins to help them move across the membrane because the lipid layer of the membrane acts as a barrier for these charged particles.

Active transport is another process that moves molecules against their concentration gradient. This type of transport requires energy, usually in the form of ATP, as molecules are moving from an area of lower concentration to an area of higher concentration, which is not energetically favorable without the input of additional energy.

Answer 2

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.