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Transcript
Cell Boundaries Vocab Cell membrane (phospho)lipid bilayer Cell wall Prokaryote Eukaryote High Concentration Low concentration Solute Solvent Equilibrium Diffusion Osmosis Selectively permeable Hypertonic Hypotonic Isotonic Protein channels Facilitated diffusion Active Transport Concentration gradient Endocytosis Phagocytosis Pinocytosis Exocytosis Objectives 1. What are the main functions of the cell membrane and the cell wall? 2. What happens during diffusion? 3. What is osmosis? Cell Membrane All cells are surrounded by a thin, flexible barrier known as the cell membrane. The cell membrane regulates what enters and leaves the cell and also provides protection and support. Cell Membrane Cell Membrane The composition of nearly all cell membranes is a double-layered sheet called a lipid bilayer. It functions as a flexible barrier between the cell and its surroundings. Lipid bilayer Cell Membrane Most cell membranes contain protein molecules embedded in the lipid bilayer. Carbohydrates are for recognition purposes. Protein channel Cell Wall (plants) The main function of the cell wall is to provide support and protection for the cell. Cell Wall Cell walls are found in plants, algae, fungi, and many prokaryotes. The cell wall lies outside the cell membrane. Most cell walls are porous enough to allow water, oxygen, carbon dioxide, and certain other substances to pass through easily. Diffusion Through Cell Boundaries The cell membrane regulates movement of dissolved molecules from the liquid on one side of the membrane to the liquid on the other side. Diffusion Particles move from an area of more concentration to an area of less concentration. This process is called diffusion. When the concentration of the solute is the same throughout a system, the system has reached equilibrium. High vs Low Concentration Diffusion Substances diffuse across membranes without requiring the cell to use energy. Diffusion A) There is a higher concentration of solute on one side of the membrane as compared to the other side of the membrane Diffusion B) Particles move from the side of with a higher concentration to the side of the membrane with a lower concentration. The solute particles will continue to diffuse across the membrane until equilibrium is reached. Diffusion C) When equilibrium is reached, solute particles continue to diffuse across the membrane in both directions. Equilibrium is a balance of molecules on either side of the membrane Osmosis Osmosis is the diffusion of water through a selectively permeable membrane. Osmosis Water tends to diffuse from a highly concentrated area of water to a less concentrated area of water. hypertonic (“above strength”): the more concentrated solution hypotonic (“below strength”): the more dilute solution isotonic (”same strength”): When concentrations of solutions are the same on both sides of a membrane Facilitated Diffusion Cell membranes have protein channels that act as carriers, allowing certain molecules to cross. The movement of specific molecules across cell membranes through protein channels is known as facilitated diffusion. Facilitated Diffusion Only specific materials can enter or exit through each type channel. Active Transport Sometimes cells move materials in the opposite direction from which the materials would normally move—that is against a concentration gradient. This process is known as active transport. Active transport requires ENERGY. Active Transport Examples: Endocytosis is the process of taking material into the cell. Phagocytosis: Solids or large molecules moved Pinocytosis: Liquids moved Exocytosis removes materials from the cell.