7-3: Cell Boundaries Biology 1

All cells are surrounded by a thin, flexible barrier Introduction All cells are surrounded by a thin, flexible barrier CELL MEMBRANE: thin, flexible barrier around a cell; regulates what enters and leaves the cell Plant cells are also supported by a strong layer CELL WALL: strong supporting layer around the cell membrane in plants, algae, and some bacteria

Cell Membrane Cell membrane regulates what enters and leaves the cell, also provides protection and support Cell membranes are made from double-layered sheets LIPID BILAYER: double-layered sheet that forms the core of nearly all cell membranes

Cell walls are present in plants, algae, fungi and prokaryotes Main function is to provide support and protection Made of mostly carbs and proteins

Diffusion Most important function of cell membrane is to move molecules from one side to other DIFFUSION: process by which molecules tend to move from an area where they are more concentrated to an area where they are less concentrated

Particles move back and forth across cell membrane Diffusion Particles move back and forth across cell membrane Particles continue moving until they are equal everywhere EQUILIBRIUM: when the concentration of a solute is the same throughout a solution When perfume is sprayed in one corner, then the whole room smells

The movement of water through the membrane of a cell Osmosis The movement of water through the membrane of a cell OSMOSIS: diffusion of water through a selectively permeable membrane

Water wants to move to where there is LESS Osmosis Water wants to move to where there is LESS ISOTONIC: when the concentration of two solutions is the same HYPERTONIC: when comparing two solutions, the solution with the greater concentration of solutes HYPOTONIC: when comparing two solutions, the solution with the lesser concentration of solutes

Facilitated Diffusion Some molecules (like sugar) pass through cells very quickly Cell membranes have “helper” proteins that allow certain molecules to cross ONLY allow specific molecule (like sugar) to pass through) FACILITATED DIFFUSION: movement of specific molecules across cell membranes through protein channels

Cell Membrane Passive Transport Great Pacific Media Cell Membrane Passive Transport http://www.youtube.com/watch?v=JShwXBWGMyY