Summary
Two layers of amphipathic lipids with hydrophilic heads outward and hydrophobic tails inward, forming the membrane core.
In depth
Each phospholipid has a hydrophilic phosphate head and two hydrophobic fatty acid tails. In water they spontaneously arrange tails inward, because hiding hydrophobic parts increases the entropy of the surrounding water. Hence membranes self-assemble and self-seal.
The bilayer is a barrier to ions and polar molecules, but flexible. Unsaturated tails and cholesterol tune fluidity: cholesterol stops the membrane being too fluid at high temperature and too rigid in the cold.
Frequently asked questions
What is Phospholipid Bilayer?
Two layers of amphipathic lipids with hydrophilic heads outward and hydrophobic tails inward, forming the membrane core.
Which area of biology covers Phospholipid Bilayer, and how advanced is it?
Phospholipid Bilayer is one of the 52 topics in Cell Biology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Fluid Mosaic Model, Cell Wall, Plasma Membrane.
Can you give an example of Phospholipid Bilayer?
Cold-adapted organisms contain more unsaturated fatty acids in their membranes to stay fluid.
What should I learn before Phospholipid Bilayer?
Work through the Beginner topics in Cell Biology first, such as Cell Theory, Prokaryotic Cell, Eukaryotic Cell, then return to Phospholipid Bilayer. Intermediate topics assume the Beginner vocabulary.
What topics are related to Phospholipid Bilayer?
The closest topics to Phospholipid Bilayer are Fluid Mosaic Model, Cell Wall, Plasma Membrane, Osmosis. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Phospholipid Bilayer?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Phospholipid Bilayer. To practise the whole of Cell Biology, use the Cell Biology quiz.
How is Phospholipid Bilayer different from Fluid Mosaic Model?
Phospholipid Bilayer: Two layers of amphipathic lipids with hydrophilic heads outward and hydrophobic tails inward, forming the membrane core. Fluid Mosaic Model: Describes the membrane as a flexible fluid bilayer in which proteins float and move laterally like a mosaic. Read both side by side and note what each one explains.
How should I study Phospholipid Bilayer step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Fluid Mosaic Model and explain the difference aloud. Finally, take the Cell Biology quiz and come back to this page for any question you miss.