How does the structure of a phospholipid bilayer contribute to the selective permeability of cell membranes?

Answer 1

In order to understand the actions of the phospholipid bilayer, one must first understand the foundational physiology. Basic rules of science is that particles strive to be in an environment with particles that behave the same as they do.

The heads of the phospholipid bilayer are hydrophilic ("water loving"), so water soluble materials like proteins can come into contact and enmesh within the phospholipid bilayer. The tails which are located internally are hydrophobic, so when water soluble particles interact with these structures they quickly shoot through the environment hoping to once again hit a water soluble environment. This interaction is similar to repulsion when holding 2 magnets positive ends together. This is referring to the free transport of specific molecules across cellular surface.

Another component to consider is the small holes in a cell's surface that allows for transport of small ions and molecules. These "holes" can either be referring to free diffusion that occurs due to charges and polarity or small transporter proteins that operate through the use of ATP.

This is how transport occurs across a cellular membrane.

Answer 2

The phospholipid bilayer contributes to the selective permeability of cell membranes in several ways:

1. Hydrophobic core: The nonpolar tails of the phospholipids create a hydrophobic core that prevents polar or charged molecules from passing through the membrane easily.

2. Selective transport: The bilayer's structure allows certain molecules to pass through while restricting others, depending on their size, charge, and polarity.

3. Embedded proteins: Proteins embedded in the bilayer can facilitate the transport of specific molecules across the membrane, either through passive or active transport mechanisms.

This selective permeability allows the cell to control the movement of substances in and out, maintaining homeostasis and regulating the internal environment.

Answer 3

The cell membrane’s structure primarily comprises a phospholipid bilayer, where each phospholipid molecule has a hydrophilic (water-attracting) head and two hydrophobic (water-repelling) tails. The hydrophilic heads face outward toward the aqueous environments inside and outside the cell, while the hydrophobic tails face inward, away from water. This arrangement creates a semi-permeable barrier that allows small, nonpolar molecules (such as oxygen and carbon dioxide) to diffuse freely across the membrane, preventing the passage of large or polar molecules and ions. Proteins embedded in the bilayer facilitate the selective transport of these substances. This selective permeability is essential for maintaining homeostasis, allowing the cell to control its internal environment.