Understanding Cell Boundaries: Membranes, Diffusion, and Transport Mechanisms
The cell membrane is crucial for regulating what enters and exits the cell, providing protection and support. Comprised of a lipid bilayer, it forms the core of nearly all cell membranes. In contrast, the cell wall mainly provides structural support and protection, allowing water and gases to pass freely. Key processes such as diffusion, osmosis, and facilitated diffusion enable substances to move across membranes, often without energy. Active transport and processes like endocytosis and exocytosis play essential roles in cellular material management.
Understanding Cell Boundaries: Membranes, Diffusion, and Transport Mechanisms
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Presentation Transcript
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
