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Cell Boundaries. Cell Membrane. The cell membrane regulates what enters and leaves the cell and also provides protection and support. Lipid bilayer -double –layered sheet that forms the core of nearly all cell membranes. Cell Walls.
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Cell Membrane • The cell membrane regulates what enters and leaves the cell and also provides protection and support. • Lipid bilayer-double –layered sheet that forms the core of nearly all cell membranes.
Cell Walls • The main function of the cell wall is to provide support and protection for the cell. • Most cell walls are porous enough to allow water, oxygen, carbon dioxide and other substances to pass through easily. • Plant cell walls are mostly cellulose, a component of wood and paper.
Diffusion through cell boundaries • Diffusion- the process by which molecules tend to more from an area where they are more concentrated to an area where they are less concentrated. • Concentration- the mass of solute in a given volume of solution. • Cytoplasm is a solution that has many different substances in water. • How diffusion works
Diffusion through cell boundaries continued • In a solution particles move constantly. • When the concentration of the solute is the same through out they system, the system has reached equilibrium. • Because diffusion depends upon random particle movements, substances diffuse across membranes with out requiring the cell to use energy.
Osmosis • Osmosis- is the diffusion of water through a selectively permeable membrane. • How osmosis works
How Osmosis Works • Isotonic- concentration of two solutions is the same. • Hypertonic-the solution with the greater concentration • Hypotonic-the solution with the lesser concentration.
Osmotic Pressure • Osmotic pressure is the pressure which needs to be applied to a solution to prevent the inward flow of water across a semi-permeable membrane.
Facilitated Diffusion • Facilitated diffusion-movement of specific molecules across cell membranes through protein channels. • How facilitated diffusion works
Active Transport • Active Transport-energy –requiring process that moves material across a cell membrane against a concentration difference
Endocytosis and Exocytosis • Endocytosis- process by which a cell takes material into the cell by infolding of the cell membrane. • Exocytosis- process by which a cell releases large amounts of material. • How it works
Exocytosis • Phagocytosis- process in which extensions of cytoplasm surround and engulf large particles and take them into the cell. • Pinocytosis- process by which a cell takes in a liquid from the surrounding environment • How it works