Transport In & Out of Cell Sections 3.3 – 3.4 Biology 391 Overview • Purpose of Transport – Laws of Nature (thermodynamics) • Passive Transport – Diffusion – Osmosis – Facilitated Diffusion Types of Transport ACTIVE PASSIVE requires Energy Does not need energy Ion Pumps Diffusion Exocytosis Osmosis Endocytosis Facilitated Diffusion • Active Transport – Ion pumps – Endocytosis & Exocytosis Review • What 3 things determine whether substances cross the plasma membrane? • What are some examples of what crosses and what does not? Terms to know • A solution is a mixture of two or more substances, evenly mixed – The cytoplasm is a solution of many different substances – Solutes = term for the substance dissolved in liquid – Solvent = the substance that dissolves the solute • Concentration = mass of solute in a given volume of solution – Mass/volume Substances move by DIFFUSION • Solutions try to achieve equilibrium – Dynamic equilibrium • Solutes will randomly move and try to spread out as evenly as possible – Entropy in the universe will tend to increase • Substances will try to be equally concentrated on the outside & inside of the cell membrane Factors that Affect Diffusion • Amounts of substances involved • Temperature • Pressure • Stirring -speeds up the rate of diffusion Passive Transport [High] to [Low] • DIFFUSION • FACILITATED DIFFUSION • OSMOSIS OSMOSIS • Deals with movement of water – From greater to lesser area of water • Particles can’t move because membrane won’t allow it! • When talking about cells… – consider membrane only soluble to water (unless told otherwise) – Concentration is relative to cytoplasm Types of Solutions the focus is on the particles (a lot or a little) in a particular solution. But the action of water in response to this environment is what we are concerned about. If the cell is placed in … • Hypotonic solution – Solution that contains a smaller concentration of substance than what is found in the cell (therefore “more water”) Water will _____________ the cell • Hypertonic – Solution that contains a larger concentration of substance than what is found in the cell (“less water”) Water will _____________ the cell • Isotonic – Concentration of substance outside the cell is the same inside the cell Water will _____________ Osmosis Osmotic Pressure • Pressure exerted on hypertonic side of a selectively permeable membrane – Cell walls prevent the cell from expanding • Some organisms fight osmotic pressure by using a contractile vacuole – pumps excess water out of the cell – Paramecium – http://www.youtube.com/watch?v=iG6Dd3COug4&feature=related Osmotic Pressure Effects of osmosis crenate cytolysis Turgor pressure RECAP • What are 3 major types of passive transport? • What characterizes these as passive? • Describe how the concentration of molecules moves within this type of transport. • What would happen to a red blood cell placed in a hypertonic solution? Active Transport • ENERGY NEEDED! Molecule to be carried – Mainly in the form of ATP • Molecules go from lesser to greater concentration “against concentration gradient” Energy • Also when LARGE molecules need to get through membrane • May or may not need channel proteins – called pumps Molecule being carried Explain this slide Endocytosis and Exocytosis • Endocytosis = process by which cells take in large molecules from the outside -eg.: pinocytosis – large amounts of liquid phagocytosis – large amounts of solid • Exocytosis = process by which cells get rid of large molecules in the cell; leaves cell. • Vesicle fuses with membrane to dispel Pinocytosis • Pinocytes are pockets on the cell membrane. • Subtances are engulfed and a vacuole forms around them Phagocytosis: Engulfing • This is when large molecules are surrounded and pulled into the cell • Examples: amoeba, white blood cells called phagocytes • This is the same method used by white blood cells to trap bacteria in our blood RECAP • What are some examples of active transport? • Describe the concentration gradient involved in active transport • How is active transport different from passive transport? • What’s happening in this picture? Exit Questions • When is equilibrium reached? • What is the difference between osmosis and diffusion? • What is the difference between active and passive transport? • A homeowner contracts a lawn company to make the grass grow better. This process is normally done by spraying a mixture of fertilizer and water onto the lawn. • What would happen if too much fertilizer and too little water were sprayed onto the lawn? • What happens to the cells of the grass? • Was the fertilizer/water mix hypertonic or hypotonic to the cells of the grass?