BIOL107 Lecture 6: BIO107 – Lecture 6-Cell Transport, Cytotic Transport
SchoolUniversity of Alberta
DepartmentBiology (Biological Sciences)
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BIO107 – Lecture 6- Cell Transport, Cytotic Transport
Cell Transport Recap:
Diffusion: movement of a solute from an area of high concentration to an area of low
• Things cannot diffuse from an area of low concentration to an area of high concentration;
cannot go against the concentration gradient.
• Water can diffuse through a membrane but it is very inefficient.
Osmosis: High energy water moves toward low energy water.
How do Solutes get Across the Plasma Membrane?
Figure 1.Types of transport across membranes.
• Passive Channels
• Passive and Active Transporters
Transport Through the Membrane: Simple Diffusion
Diffusion through the phospholipid bilayer:
• “Small” non-polar substances
➢ Examples: Carbon Dioxide (CO2), Oxygen (O2), Steroid Hormones
It is possible for water to diffuse through the membrane, but it is very inefficient.
Transport through the membrane: Passive Transport- Channels
Channels provide facilitated diffusion (a structure that facilitates/ helps the process of
diffusion) of ions and water without requiring energy.
• Channels facilitate the diffusion of molecules from one side of the membrane to the
• Since these channels are passive they do not require energy, and generally remain the
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