Diffusion Osmosis Movement Across the Cell Membrane Lab Report

Diffusion Osmosis Movement Across the Cell Membrane Lab Report

Worksheet Diffusion/Osmosis/ Membranes Label the three images below as isotonic / hypertonic / or hypotonic with respect to the solution the cell is placed in Choose the correct word in the below statements: -Movement across the cell membrane that does not require energy is called active / passive transport -The difference in the concentration of a substance across a space is called a concentration equilibrium / gradient. -If a concentration gradient exists, substances will move from an area of high / low concentration to an area of high / low concentration. -The plasma membrane of a cell is impermeable / selectively permeable -The diffusion of water through a selectively permeable membrane is called diffusion / osmosis. -The process of taking large molecules into a cell by in-folding the cell membrane is called endocytosis / exocytosis. -Facilitated diffusion moves substance up / down their concentration gradient. Work out each of the following problems: 1. A dialysis bag filled with 0,2% glucose is placed into a beaker containing 10% glucose. The dialysis bag has a pore size that will allow the passage of water, but not glucose molecules. At the start of the experiment, 1) which way will water move, into or out of the dialysis bag, and 2) describe the tonicities of the water in the bag and in the beaker at the start of the experiment 2. Two beakers are set up with a connecting tube that contains a semipermeable membrane that will allow water molecules to pass through, and will also allow fructose molecules to pass through. At the start of the experiment, the left beaker contains 10% fructose, and the right beaker contains 0.5% fructose. At the start of the experiment, 1) which way will water move ? 2) which way will fructose move? 3) which beaker is hypotonic and which is hypertonic? 3. Sheep red blood cells are added to a beaker containing a solution of 0.2% NaCl. What will happen to the cells? Describe the tonicities of the cells and the solution in the beaker? MEMBRANES AND TRANSPORT 1 2 MEMBRANE FUNCTIONS • Semi-permeable membrane • Control of exchange of materials • Organization of cellular functions • Cellular communication and signal transduction • Cell to cell recognition • Transformation of energy • Cell adhesion 3 WHAT ARE THE MOLECULAR COMPONENTS THAT MAKE UP THE PLASMA MEMBRANE? • Lipids • Phospholipids • Glycoproteins & glycolipids • (protein or lipid + carbohydrate) • Found on exterior of cell only • Steroids (cholesterol) • Proteins • Carbohydrate (Glycocalyx) 4 PHOSPHOLIPID BILAYER • Constructed from phospholipids • Bilayer is formed • Outside hydrophillic; inside hydrophobic • “soap bubble” 5 STEROIDS & GLYCOLIPIDS • Cholesterol increases or decreases membrane fluidity 6 PROTEINS 7 THE FLUID MOSAIC MEMBRANE MODEL • Fluid phospholipid layers • Collage of proteins embedded in the matrix • Not completely homogeneous; microdomains present (lipid rafts) 8 DIFFUSION • Tendency for molecules to move from areas of high concentration to areas of lower concentration • Based on kinetic energy intrinsic to molecules 9 DIFFUSION OF WATER:OSMOSIS • Diffusion of solvent (H2O) • Tonicity of Solutions • Isotonic • Hypotonic • Hypertonic 10 TONITICY OF SOLUTIONS • Isotonic environment • Water concentration outside = water concentration inside the cell • Or water concentration is the same on both sides of a semi-permeable membrane • Most cells contain about 0.9% dissolved salts • An isotonic environment must contain about 0.9% dissolved salts (solutes) 11 HYPOTONIC • Hypotonic environment • Water concentration outside of cell is higher than inside cell (solute concentration outside cell is lower than inside cell) • Result: water moves into cell at a greater rate than it moves out • Solution with lowest concentration of solute is described as hypotonic 12 HYPERTONIC • Water concentration outside cells is lower than inside cell (solute concentration outside cells is higher than inside cell) • Result: water moves out of cell at a greater rate than it moves in • Solution with highest concentration of solute is described as hypertonic OSMOTIC CONDITIONS Isotonic to the cell Na+ ClRed Blood cell Flow of water into the cell = flow of water out of the cell Osmotic Conditions Hypotonic to the cell Na+ Cl- Water (osmosis) Cell will swell and lyse (burst) Osmotic Conditions Hypertonic to the cell Na+ Cl- Water (osmosis) 16 TONICITY WORKSHEET 17 OSMOSIS EFFECTS ON CELLS 18 MOVEMENT OF OTHER SMALL MOLECULES • Three possible types of transport for molecules • Diffusion • Passive transport • a.k.a. facilitated diffusion • Based on diffusion • No energy required • Active transport • Requires an expenditure of energy • https://www.youtube.co m/watch?v=jQN07Hvq6 WI 19 PASSIVE TRANSPORT PROTEINS • Passive transport • • • • No energy input required Open or gated channels Carrier Proteins Overall movement is from high concentration to low https://www.youtube.com/watch?v=8HlVy__J8XA 20 ACTIVE TRANSPORT • Active Transport • Requires that a cell expend energy to move molecules across a membrane • A transport protein actively pumps a specific solute across a membrane against the solute’s concentration gradient • Systems like this are common, coupling the passage of two solutes; they can transport ions as well as uncharged molecules • Usually use ATP as energy source 21 FUNCTIONS OF ACTIVE TRANSPORT • Three main functions for active transport • Cell can uptake molecules against a concentration gradient • Molecules can be moved out of cell against concentration gradient • Cell can maintain optimal concentrations of ions 22 ACTIVE TRANSPORT • Active transport • Transport protein uses energy (usually ATP) to pump a solute across a cell membrane against concentration gradient • Examples • Sodium potassium pump 23 • Example • https://www .khanacade my.org/scie nce/biology /membrane s-andtransport/ac tivetransport/v/s odiumpotassiumpump-video SODIUM POTASSIUM PUMP 24 CFTR IS A GATED CHANNEL PROTEIN THAT REQUIRES ATP • .youtube.com/watc h?v=_j99xgOIaw&t=106s 25 TRANSPORT OF LARGE MOLECULES: BULK TRANSPORT • Movement of large molecules or particles into or out of cell requires active transport • Two types • Exocytosis: exports molecules from the cell • Endocytosis: brings molecules into the cell 26 EXOCYTOSIS • Exports materials 27 ENDOCYTOSIS • Three types • Pinocytosis • Receptormediated endocytosis • Phagocytosis

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