Hydrophobic Tail

Definition

The hydrophobic tail is a non-polar, hydrocarbon chain that is a key structural component of lipids. This tail is repelled by water and prefers to interact with other non-polar, hydrophobic molecules, allowing lipids to self-assemble into important biological structures like cell membranes.

5 Must Know Facts For Your Next Test

1. The hydrophobic tail of lipids is typically a long, straight chain of 16-18 carbon atoms with hydrogen atoms attached.
2. The hydrophobic nature of the tail allows lipids to spontaneously self-assemble into structures like the bilayer of cell membranes, with the tails facing inward and the hydrophilic heads facing outward.
3. Unsaturated fatty acids, which have one or more carbon-carbon double bonds, have kinks in their hydrophobic tails that affect the packing and fluidity of lipid bilayers.
4. The length and degree of saturation of the hydrophobic tails influence the melting point and overall properties of lipids, impacting their biological functions.
5. Cholesterol, a steroid lipid, inserts its hydrophobic steroid ring structure into the hydrophobic core of cell membranes, modulating their fluidity and permeability.

Review Questions

• Explain how the hydrophobic nature of the lipid tail contributes to the self-assembly of lipid bilayers in cell membranes.
  • The hydrophobic tails of lipid molecules are repelled by water and prefer to interact with each other, rather than with the surrounding aqueous environment. This drives the spontaneous self-assembly of lipids into a bilayer structure, where the hydrophobic tails are shielded from water and face inward, while the hydrophilic heads face outward and interact with the aqueous surroundings. This amphipathic arrangement of the lipid molecules is crucial for the formation and stability of cell membranes, which serve as a selectively permeable barrier to regulate the flow of materials in and out of the cell.
• Describe how the length and degree of saturation of the hydrophobic tails influence the properties and functions of lipids in biological systems.
  • The length and degree of saturation of the hydrophobic tails of lipids have a significant impact on their physical and functional properties. Longer tails, typically 16-18 carbon atoms, result in higher melting points and increased packing density within the lipid bilayer, making the membrane more rigid and less permeable. Conversely, unsaturated fatty acids with carbon-carbon double bonds introduce kinks in the hydrophobic tails, reducing their ability to pack closely together, leading to increased fluidity and permeability of the membrane. These variations in lipid properties allow for the fine-tuning of membrane functions, such as regulating the activity of membrane-bound proteins, facilitating cellular signaling, and maintaining the appropriate barrier properties for different cell types and organelles.
• Analyze the role of cholesterol and its hydrophobic steroid ring structure in modulating the properties of cell membranes.
  • Cholesterol, a steroid lipid, plays a crucial role in regulating the fluidity and permeability of cell membranes. The hydrophobic steroid ring structure of cholesterol inserts into the hydrophobic core of the lipid bilayer, interacting with the hydrophobic tails of other lipid molecules. This interaction has several effects on membrane properties: it reduces the mobility and packing of the lipid tails, increasing membrane fluidity; it also decreases the permeability of the membrane to small, water-soluble molecules, acting as a barrier. Additionally, the presence of cholesterol in the membrane helps maintain its structural integrity and influences the activity of membrane-bound proteins, which are essential for various cellular functions. The ability of cholesterol to modulate membrane properties is vital for maintaining the appropriate balance of fluidity and permeability required for proper cell function and signaling.

Related terms

Phospholipid: A type of lipid molecule that contains a hydrophilic (water-loving) head and two hydrophobic tails, allowing it to form the bilayer structure of cell membranes.

Fatty Acid: A long, hydrocarbon chain with a carboxyl group at one end, which makes up the hydrophobic tail region of many lipid molecules.

Amphipathic: Having both hydrophilic (water-loving) and hydrophobic (water-fearing) regions, a characteristic of many lipid molecules like phospholipids.