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Transcript
Cell Boundaries How is a window screen like a cell membrane? What are some things that can pass through a window screen? What are some things that cannot? Why is it important for a cell membrane to regulate what moves into and out of a cell? PSRs Prefixes, Suffixes, Roots Cyto – cell Hyper – above Iso – equal Phag – eat Semi – half Endo – within/inside Hypo – beneith Trans – across Exo – outside Per – through/beyond Write these PSRs in your journal Cell Borders Cell Membrane (semi-permeable) Controls what enters and leaves cell. made of Phospholipid bilayer 2 layers of phospholipids with a “mosaic” of proteins and carbs. (In ALL cells!) Cell Wall – (in plants) Provides support and protection. made of cellulose – a tough carb. 2 Ways to Cross the Membrane Passive Transport – NO energy is required to move a substance across the membrane (moves along gradient) Active Transport – Energy IS REQUIRED to move a substance across the membrane (moves against gradient) Passive Transport - Diffusion Diffusion - movement of particles from areas of high concentration of solute to areas of low concentration of solute. What is concentration? What is a solute? When the concentration is the same throughout, equilibrium is reached. Temperature and size of molecule affect the rate of diffusion. Diffusion Animation Passive Transport - Osmosis Osmosis – the diffusion of water particles across a membrane. Water moves from low solute to high solute. Why is osmosis important for cells? Animated demonstration How Osmosis Works in the Cell Isotonic – Concentration of solutes outside and inside cell are equal. – water moves in and out at the same rate Equilibrium Hypertonic - Concentration of solutes outside is higher than inside the cell. Water out Hypotonic - Concentration of solutes outside is lower than it is inside the cell. Water in 1. Animated Review of Hypertonic, Hypotonic and Isotonic Solutions What type of solution are these cells in? A Hypertonic B Isotonic C Hypotonic Passive Transport: Facilitated Diffusion Facilitated Diffusion – Large molecules (like glucose) move across the membrane with the help of protein channels. Moves from high concentration of molecules to low – no energy required. Diffusion / Passive Transport Active Transport = ATP Active Transport Larger molecules (sugar) and ions (Na+, K+, Ca+2) pass across the membrane using proteins using ENERGY. Substances move from low to high concentrations. Active Transport: Exocytosis and Endocytosis Exocytosis - Wastes and products are packaged in vesicle by the Golgi and sent OUT of cell Endocytosis – cell membrane forms vesicle and brings things INTO the cell. 7. TRANSPORT of LARGE PARTICLES WATCH VIDEO OF ENDOCYTOSIS, FORMATION OF FOOD VACUOLES OF PARAMECIUM Endocytosis (Endo = In): cell surrounds and takes in material from environment. Material does not pass through the membrane; instead, it is engulfed and closed by a portion of membrane and cytoplasm. Pinocytosis: water Phagocytosis: food/ minerals/ large particles Exocytosis (Exo = Out): transport of materials out of cell across cell membrane. WATCH VIDEO OF EXOCYTOSIS, SECRETION OF FOOD VACUOLES FROM PARAMECIUM Exocytosis secreted material (extracellular fluid) plasma membrane plasma membrane 2 3 1 vesicle (cytoplasm) 0.2 micrometer Types of Endocytosis – engulfs by surrounding membrane around solids. Phagocytosis “Phago-” means “to eat” – pinches membrane and brings in liquids. Pinocytosis “Pino-” think “to pinch” (a) pinocytosis (extracellular fluid) Click on Active Transport, watch the brief overview of Active Transport and then click on Endocytosis in the bar below the animation 1 2 Animated Review of Phagocytosis, Pinocytosis and Receptor Mediated Endocytosis. 3 vesicle containing extracellular fluid (cytoplasm) cell (b) phagocytosis food particle pseudopod 1 2 3 particle enclosed in vesicle