Selective Permeability and Molecular Transport

The cell membrane's selective permeability determines which molecules can pass through it.

Example: Small uncharged polar molecules, gases, and lipid-soluble molecules can pass easily through the membrane.

Highlight: Ions, large hydrophilic molecules, and proteins cannot pass easily through the membrane without assistance.

Definition: Selective permeability allows only specific substances to cross the membrane barrier, maintaining cellular homeostasis.

Cell Membrane Fundamentals and Structure

The cell membrane, also known as the plasma membrane, forms the fundamental barrier between a cell's internal and external environment. This phospholipid bilayer structure serves multiple essential functions in cellular operation and survival.

Definition: The cell membrane is a phospholipid bilayer that regulates molecular entry and exit while maintaining cellular homeostasis.

Highlight: The membrane's fluidity and flexibility result from unsaturated fatty acid chains and varying chain lengths in its structure.

Example: The membrane performs five key functions: containing cytoplasm, providing protection, regulating molecular transport, anchoring the cytoskeleton, and enabling cell-to-cell recognition.

Vocabulary: Homeostasis refers to maintaining stable internal conditions despite external environmental changes.