MOVEMENT THROUGH THE MEMBRANE Bubble Lab Section 7-3 The cell membrane вЂў Function: вЂў Regulates what enters and leaves the cell. Provides protection and support вЂў Selective permeability вЂў Some substances can pass across the cell membrane and others canвЂ™t Structure Phospholipid Bilayer (Fluid Mosaic Model): a double-layer sheet that makes up nearly all membranes. Components of the lipid bilayer вЂў Polar Head вЂ“ Hydrophilic вЂњWater LovingвЂќ вЂў Lipid Tails вЂ“ Hydrophobic вЂњWater FearingвЂќ Why is the lipid bilayer important? вЂў Tough, flexible structure вЂў Strong barrier between the cell and its environment What does it do for the cell? вЂў Allows only certain materials in or out at certain times. вЂ“Ions вЂ“Glucose вЂ“Water вЂ“Electrolytes Other membrane structures вЂў Protein molecules вЂ“Form channels and pumps that help to move material across the membrane Other Membrane Structures вЂў Carbohydrate molecules вЂ“Act like ID markers for the cell вЂ“Basis for blood typing: the antigens on the blood cells (A, B, AB) are carbohydrate chains вЂў Cells live in fluid environments, with water inside and outside the cell. вЂў Components of plasma membrane: вЂ“2 layers of phosphlipids вЂў Polar head and nonpolar tail вЂ“Integral proteins вЂ“Peripheral proteins вЂ“Cholesterol вЂ“Carbohydrates вЂў Proteins: вЂў Peripheral proteins вЂў On inside surface вЂў Held in place by cytoskeletal filaments вЂў Integral proteins вЂў Embedded in membrane, can move laterally вЂўCholesterol - strengthens the plasma membrane. вЂўCarbohydrates: вЂўGlycoproteins вЂ“ proteins with carbohydrates attached вЂўGlycolipids вЂ“ phospholipids with carbohydrates attached Functions of membrane proteins вЂў Some help to transport materials across the membrane. вЂўChannel Protein вЂ“ allows certain molecules or ions to cross membrane freely вЂўCarrier Protein вЂ“ interacts with certain molecule or ions to help move it across membrane вЂў Some proteins aid in cell recognition вЂ“ Glycocalyx - In animal cells, the carbohydrate chains of cell recognition proteins are collectively called this Cell recognition protein вЂўForeign carbohydrate chains are why transplanted tissue is often rejected by the body Building A Membrane 1. Using the materials provided to you, build a model of a cell membrane. 2. Make a key explaining what pieces represent the Polar Head, Lipid Tails, Protein Molecules, and Carbohydrate Molecules 3. Have your teacher check your model before you eat it! Diffusion Definition: The movement of molecules from an area of higher concentration to an area of lower concentration, until equilibrium is reached. Concentration? Mass of Solute/Volume of solution (g/L) Diffusion of Molecules What causes diffusion? вЂў Diffusion is caused by the constant movement and collision of molecules. More molecules = More collision вЂў The collision cause the molecules to spread out. Diffusion in Cells Molecules are able to diffuse through the cell membrane and allow the cell to function. Facilitated Diffusion вЂ“ some molecules need help from protein channels to cross the cell membrane. Animation Osmosis (A special kind of diffusion) Osmosis is the diffusion of water molecules through a selectively permeable membrane. Selectively Permeable - Osmosis Osmosis Isotonic вЂ“ concentration is the same on both sides of the membrane (equilibrium) Hypertonic вЂ“ the solution with a greater concentration Hypotonic вЂ“ the solution with the lesser concentration. Osmosis Practice The cytoplasm of Elodea cells is composed of about 70% water molecules and 30% other kinds of molecules. What happens when the Elodea cells are put into a liquid that is a. 50 percent water. b. 70 percent water. c. 100 percent water . Active Transport Moving down a concentration gradient is like riding a bike down a hill. It doesnвЂ™t require energy Osmosis and diffusion are examples of passive transport! Moving up a concentration gradient is like riding up a hill. IT REQUIRES ENERGY. Active Transport вЂў Active Transport: is the movement of materials through a cell membrane using energy. вЂў Molecules move from low concentration to high concentration. вЂў Proteins use ATP to pump ions and small molecules against concentration gradient. Types of Active Transport 1. Endocytosis вЂ“ the process of taking material into the cell by means of infoldings of the cell membrane. вЂ“ Phagocytosis вЂ“ extension of the cytoplasm surround and engulf the particle вЂ“ Pinocytosis вЂ“ similar to phagocytosis, but cells take up liquid instead of particles. Types of Active Transport 2. Exocytosis вЂ“ Large molecules move from inside the cell to outside the cell. вЂ“ Contractile Vacoule вЂ“ an organelle that constantly pumps H2O out of the cell. Animation Specialized Cells вЂў Cells with a specific structure and function and are found in multi-celled organisms. вЂў We have blood cells, brain cells, bone cells, liver cell, skin cells, etc. We are all made of cells Organ System Organs Tissues Cells Tissue вЂў Definition: A group of similar cells working together. вЂў Examples Organs вЂў Definition: A groups of tissues working together to perform a specific job. Organ Systems вЂў вЂў Definition: Many organs working together to do a specific job. Can you name all 10 organ systems? 7.3-7.4 Wrap up Questions 1. 2. 3. 4. 5. Explain Diffusion Explain Osmosis What does selectively permeable mean? What is facilitated diffusion? Are phospholipids the only molecules in a cell membrane? 6. What is active transport? 7. What are tissues, organs, and organ systems? Give Examples = cell 10% salt 10% salt 10% salt 20% salt 20% salt 10% salt Label the environment around the cell in each beaker as hypertonic, hypotonic or isotonic. Label the net flow of water and state what will happen to the cell in each beaker? = cell 10% salt 10% salt 10% salt 20% salt 20% salt 10% salt Label the environment around the cell in each beaker as hypertonic, hypotonic or isotonic. Label the net flow of water and state what will happen to the cell in each beaker? = cell 10% salt 10% salt 10% salt 20% salt 20% salt 10% salt Label the environment around the cell in each beaker as hypertonic, hypotonic or isotonic. Label the net flow of water and state what will happen to the cell in each beaker? Cell membrane reading questions 1. Compare and contrast integral and peripheral proteins. 2. What are the differences between the two types of transport proteins discussed in the article (use figure 7.10 to help you) 3. Why are proteins so essential to keeping your cells hydrated? 4. Explain how diffusion relates to a concentration gradient.