Cell Membrane & The Ways Molecules Move

Cell Membrane & The Ways Molecules Move I. Cell Membrane 1) POLAR ends face INSIDE & OUTSIDE cell [where water is] 2) NONPOLAR tails face each other inside bilayer [to avoid water] Cell Membrane & The Ways Molecules Move

Cell Membrane & The Ways Molecules Move Outside of cell Inside (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains Cell Membrane & The Ways Molecules Move 3

Cell Membrane & The Ways Molecules Move II. FUNCTION: SELECTIVE PERMEABILITY = allows only certain materials to go into & out of cell Cell Membrane & The Ways Molecules Move 4

Cell Membrane & The Ways Molecules Move a. Why doesn’t the cell membrane let everything through? HOMEOSTASIS! - Cells maintain a stable environment by controlling what enters & leaves. Cell Membrane & The Ways Molecules Move

III. Cellular Transport – Two Major Types (Passive & Active Transport) Cell Membrane & The Ways Molecules Move Passive Transport = moves molecules across cell mem. using NO ENERGY Movement going with the concentration gradient (normal flow) Cell Membrane & The Ways Molecules Move

Cell Membrane & The Ways Molecules Move A. Types of Passive Transport Diffusion – molecules move from HIGH conc. to LOW conc. a. Small molecules: O2, CO2 b. Slow process Cell Membrane & The Ways Molecules Move

Cell Membrane & The Ways Molecules Move

Cell Membrane & The Ways Molecules Move

Cell Membrane & The Ways Molecules Move 2. Facilitated Diffusion – movement of molecules with help of a carrier protein Cell Membrane & The Ways Molecules Move

Cell Membrane & The Ways Molecules Move

Cell Membrane & The Ways Molecules Move Moves large molecules like Glucose and Fructose (C6H12O6) b. Faster than diffusion Cell Membrane & The Ways Molecules Move

Cell Membrane & The Ways Molecules Move http://www.sirinet.net/~jgjohnso/homeostasis.html Cell Membrane & The Ways Molecules Move

Cell Membrane & The Ways Molecules Move 3. Osmosis – diffusion of WATER across cell membrane * H2O moves to area with LESS WATER Cell Membrane & The Ways Molecules Move

Cell Membrane & The Ways Molecules Move a. Direction of Osmosis: 1) Hypotonic Solution = H2O moves INTO cell & CELL EXPANDS Cell Membrane & The Ways Molecules Move

Cell Membrane & The Ways Molecules Move 2) Hypertonic Solution = H2O moves OUT OF cell & CELL SHRINKS Cell Membrane & The Ways Molecules Move

Cell Membrane & The Ways Molecules Move 3) Isotonic Solution = H2O moves INTO & OUT OF cell & cell stays NORMAL SIZE Cell Membrane & The Ways Molecules Move

Cell Membrane & The Ways Molecules Move

Cell Membrane & The Ways Molecules Move * EQUILIBRIUM = concentration of molecules is same everywhere * Molecules never stop moving – even at equilibrium Cell Membrane & The Ways Molecules Move

PROBLEM for Cells? Cell membranes are SELECTIVELY PERMEABLE

2. 2nd Type of Transport  Active Transport moves molecules across cell membrane using ENERGY

Cell Membrane & The Ways Molecules Move B. Types of Active Transport Cell Membrane & The Ways Molecules Move 1. Transport Proteins: in membrane- move substances from low to high conc. (opposite of how it wants to move) Cell Membrane & The Ways Molecules Move

2. Endocytosis = cell surrounds & ingests materials from OUTSIDE to INSIDE cell using VESICLES

Cell Membrane & The Ways Molecules Move http://www.sirinet.net/~jgjohnso/homeostasis.html Cell Membrane & The Ways Molecules Move

Cell Membrane & The Ways Molecules Move a. Steps: 1) membrane folds in & forms pocket 2) Pocket closes & pinches off in cell vesicle 3) vesicle fuses w/ organelles to release contents Cell Membrane & The Ways Molecules Move

Cell Membrane & The Ways Molecules Move b. Two Types of Endocytosis: Phagocytosis – LARGE particles (food) or whole CELLS (bacteria) into cell 2) Pinocytosis – large amounts of liquids/ fluids into cell Cell Membrane & The Ways Molecules Move

Cell Membrane & The Ways Molecules Move 3. Exocytosis –releases large amounts of material to the OUTSIDE of the cell using VESICLES Cell Membrane & The Ways Molecules Move

Cell Membrane & The Ways Molecules Move a. Steps: Vesicle forms, travels to & fuses w/ cell mem. Vesicle opens to outside & releases contents Cell Membrane & The Ways Molecules Move

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