Doesn’t require energy The Plasma Membrane 9/18/2018 Simple Diffusion Doesn’t require energy 14.) Moves materials from high to low concentration For example: Oxygen and water diffuses into a cell, while carbon dioxide diffusing out. G. Podgorski, Biol. 1010

The Plasma Membrane 9/18/2018 Simple Diffusion In other words, molecules move from crowded to less crowded areas of concentration. This can occur in solids, liquids, and gases. G. Podgorski, Biol. 1010

Diffusion “in action”… You might smell perfume when you sit near or walk past someone wearing it. This is because the perfume molecules are randomly moving throughout the air . The molecules are going from an areas that is crowded (such as inside the bottle) to a less crowded area (such as the air itself). There’s more space for the molecules to spread out and move in the air. Diffusion stops once there is an equal number of molecules in both areas. The molecules are in equilibrium.

The Plasma Membrane 9/18/2018 DIFFUSION Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY G. Podgorski, Biol. 1010

Diffusion of Liquids The Plasma Membrane 9/18/2018 G. Podgorski, Biol. 1010

Diffusion across a membrane The Plasma Membrane 9/18/2018 Osmosis Diffusion across a membrane 16. Diffusion of “water” across a cell membrane Moves from HIGH water potential (low solute) to LOW water potential (high solute) sem-i-permeable membrane G. Podgorski, Biol. 1010

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“Facilitated diffusion” *What does the word facilitate mean? The Plasma Membrane “Facilitated diffusion” *What does the word facilitate mean? 9/18/2018 17.) Doesn’t require energy but still needs help! It uses transport proteins to provide “doorways” to help move material from high to low concentration Examples: Glucose (sugar) or amino acids (--a chain of proteins) moving from blood into a cell. G. Podgorski, Biol. 1010

Facilitated Diffusion The Plasma Membrane 9/18/2018 Facilitated Diffusion Molecules will spontaneously move through the pores of the cell membrane with the help of “Channel Proteins” that provide a “doorway” G. Podgorski, Biol. 1010

Facilitated Diffusion The Plasma Membrane Facilitated Diffusion 9/18/2018 Carrier proteins do not extend through the membrane. They bond and drag molecules through the lipid bilayer and release them on the opposite side. G. Podgorski, Biol. 1010