Cell Transport Mechanisms

Cell Transport Revision Sheet

1. 📌 Essentials

• Cell transport involves movement of molecules across the semi-permeable membrane.
• Main types: passive (no energy) and active (energy-dependent).
• Passive transport includes diffusion, facilitated diffusion, and osmosis.
• Active transport requires ATP and transport proteins to move molecules against gradients.
• Osmosis is specifically water movement driven by solute concentration differences.
• Tonicity determines cell volume changes: isotonic, hypertonic, hypotonic.
• Plant cells tolerate hypotonic solutions via turgor pressure; animal cells risk lysis.
• Transport proteins are essential for large, charged, gradient-opposing molecules.
• Endosis and exocytosis are bulk transport mechanisms.
• Dynamic equilibrium occurs when molecular movement is balanced.

2. 🧩 Key Structures & Components

• Cell membrane — semi-permeable barrier controlling substance entry/exit.
• Transport proteins — facilitate movement of large/charged molecules.
• Channel proteins — form pores for specific ions or molecules.
• Carrier proteins — change shape to transport molecules across membrane.
• Vesicles — membrane-bound sacs for endocytosis/exocytosis.
• Water channels (aquaporins) — facilitate rapid water movement during osmosis.
• Solutes — ions, glucose, amino acids, etc., moved via different mechanisms.
• Concentration gradient — difference in solute concentration across membrane.