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Cell Surface Area to Volume Ratio • There is a limit to cell size due to volume • Cell surface to volume calculator • As cell volume increases, cell surface area can not keep up. • Think of blowing up a balloon. It may pop! • Therefore, there is a limit to cell size. WHY ARE MEMBRANES IMPORTANT? Mitochondria cell power generator have 2 NUCLEUS has a membrane ANIMAL CELLS have a large membrane PLANT CELLS have a large membrane What functions do cell membranes serve for cells? Protects what is inside Move substances in/out Holds substances Keep the cell from getting too big What type of molecules are CELL MEMBRANES made of? http://www.susanahalpine.com/anim/Life/memb.htm • • • • Hydro-water Phobic-fear Philic-love Phospho- means phosphate-PO4 • Lipid means fat LOVES WATER! ♥ AVOIDS WATER! One phospholipid shown 3 ways Chemical formula of Phosphate Chemical formula of lipid (fat) Phosphate( PO4) Sugar Lipid (fat) Proteins in the cell membrane • Integral Protein • Peripheral Protein • Channel Proteins • Penetrate both sides of the membrane • On 1 side of membrane • Embed both sides of membrane with a channel (opening) • Receptors may be on the ends of a protein to attract molecules The way a membrane looks Fluid Mosaic Model • Why call a membrane fluid? – The membrane moves all the time • What is a mosaic? – Many pieces put together to make a structure LET’S LOOK AT A MEMBRANE Two forms of Membrane Transport Tutorial You will need Flashplayer • Passive • No energy required • Active • Energy required What type of molecules move passively through a membrane? • Fat Soluble -can dissolve in fats • Since the membrane contains lipids (fat), fat soluble molecules like gases-oxygen, carbon dioxide & steroids, which is a type of fat, move through easily • Let’s watch this tutorial segment Passive transport -Molecules Move Down a Gradient from High to Low What type of molecules need assistance by proteins to move through a membrane? • Water Soluble -can’t move easily • Remember oil and water can’t mix! Since the membrane contains lipids (fat) • So, sugars, proteins, ions (charged particles) and water need help DEFINITION OF SOLUTION A MIXTURE IN WHICH ONE SUBSTANCE IS DISSOLVED INTO ANOTHER. SUBSTANCE BEING broken down IS SOLUTE. I.E SALT SUBSTANCE DOING THE DISSOLVING IS SOLVENT. I.E WATER DIFFUSION A form of Passive Transport Movement of Water, or very Small Molecules • Simple Diffusion- Movement of molecules from high concentration to low concentration • Tutorial • Water uses ____________ to move through the membrane. OSMOSIS Passive Transport • OSMOSIS MOVEMENT OF WATER Molecules • No Energy is Required • Water moves from high concentration low concentration to become equal. • water moves down a concentration gradient. • Let’s see what happens with different cells in solutions Three types of Osmotic Solutions Can you predict which way water will move? Hypotonic Solution Isotonic Solution Hypertonic Solution Red Blood Cells & Animal Cells Plant Cells 1. Which way will the water move? 2. What will happen to the water level in the tube? Hypotonic Sugar Molecules in Water membrane Hypertonic FACILITATED DIFFUSION NO ENERGY REQUIRED. Uses a transport Protein • Facilitated Diffusion- does not use energy but is assisted by transport proteins in the membrane. MEMBRANE TRANSPORT ACTIVE • ACTIVE NEEDS ENERGY • Molecules move from Low concentration to High concentration of molecules • MOVEMENT of LARGE or CHARGED PARTICLES (IONS) Animation ACTIVE TRANSPORT • It needs ? • ENERGY!!!! Why? • Going against (up) concentration gradient • Uses 2 different methods – Ion/Protein pumps-for ions, (Charged particles) – Endocytosis- large particles, uses a vacuole Ion-protein Pump Recap of Passive Active Membrane Transport Endocytosis 2 Types of Endocytosis Pinocytosis Cell Drinking Phagocytosis Cell Eating Tutorial
