Cell Membranes: The Phospholipid Bilayer | A-level Biology | OCR, AQA, Edexcel

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The key points covered of this video include:

1. The Cell Membrane
2. The Phospholipid Bilayer

The Cell Membrane

All cells contain plasma membranes - the plasma membrane that surrounds the cell is called the cell surface membrane. In eukaryotes, cells have compartments that are also enclosed in a cell membrane - these are called organelles. Cell membranes act as barriers that can control what passes into and out of cells and organelles. Cell membranes are able to achieve this due to their structure - they are composed of phospholipids.

The Phospholipid Bilayer

The cell membrane is composed of two layers of phospholipids - this is called phospholipid bilayer. A bilayer is formed due to the properties of phospholipids - they have a hydrophilic phosphate head and two hydrophobic fatty acid tails. In aqueous conditions the hydrophilic heads form two outer rows while the hydrophobic tails are protected in a non-aqueous core. The phospholipid bilayer has some important functions in the cell membrane: It creates a partially permeable barrier, It keeps the membrane fluid but stable.

Summary

All cells, including prokaryotes and eukaryotes contain a cell surface membrane
Eukaryotic cells also contain membrane-enclosed compartments called organelles
Cell membranes are composed of a phospholipid bilayer which acts as a partially permeable barrier

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