Cell Membrane and Transport PDF

CELL MEMBRANE STRUCTURE & CELL TRANSPORT  Cell Membrane ◼Maintains homeostasis ◼Selectively permeable ◼Provides protection and support ◼ALL cells have a cell membrane ◼AKA: Plasma Membrane  Fluid Mosaic Model ◼ The membrane is fluid {flexible} ◼ Different molecules e...

CELL MEMBRANE STRUCTURE & CELL TRANSPORT  Cell Membrane ◼Maintains homeostasis ◼Selectively permeable ◼Provides protection and support ◼ALL cells have a cell membrane ◼AKA: Plasma Membrane  Fluid Mosaic Model ◼ The membrane is fluid {flexible} ◼ Different molecules embedded within the membrane.  Why do you think scientists describe the cell membrane as a “mosaic”??? Because it looks like a mosaic!  Structure of the Plasma Membrane ◼ Lipid bilayer –2 layers of lipids (phospholipids). ◼ Embedded with: – Proteins –Cholesterol animation  Structure of the Cell Membrane Outside of cell Carbohydrate Proteins chains Lipid Bilayer Transport Protein Phospholipids Inside of cell Animations (cytoplasm) of membrane Go to structure Section:  There are different types of Membrane Proteins ◼ Some Speed up reactions ◼ Some Recognize {have receptors} ◼ Some Transport materials across  Glycoproteins ◼ Proteins that have sugars attached. ◼ Function~ cell recognition (chemical “identification cards”) Important in the immune system. Characteristics of Plasma Membrane ◼ Polar & Non-polar regions – Polar (water-soluble) –Hydrophilic head Facing outside & inside of cell ◼ Nonpolar fatty acids –Hydrophobic tail Middle of membrane layers  Polar & Non-Polar Reactivity ◼ Nonpolar molecules do not interact with polar molecules. –Ex. Oil (nonpolar) in water (polar) ◼ Nonpolarmolecules interact with other nonpolar molecules.  Questions ◼ What is the difference between hydrophilic and hydrophobic? ◼ Which part of the cell membrane is hydrophilic? Questions ◼ Which part of the cell membrane is hydrophobic? ◼ What is the function of the proteins?  Label (word bank below) Hydrophobic & Hydrophilic regions Head, Tail, Cytoplasm, Outside the cell, protein channels, carbohydrate chains. What is this??  Show video Cell Membrane and Transport (2 mins) Cell Transport  Movement through the Cell Membrane Can happen 2 different ways: 1. Passive Transport 2. Active Transport  Passive Transport ◼ Movement of substances across the cell membrane –without input of energy (ATP) ◼(High → Low) Three Types of Passive Transport 1. Simple Diffusion 2. Facilitated Diffusion 3. Osmosis  First Type: Diffusion ◼ Process where molecules (solutes) move from an area of HIGH concentration to an area of LOW concentration ◼ Diffusion occurs DOWN/WITH a concentration gradient  Diffusion ◼ DoesNOT require the cell to use energy (ATP)  What drives Diffusion? ◼Kinetic energy in molecules ◼ Caused by movement of particles due to the movement of their atoms. Animation Certain Factors Affect Diffusion ◼Temperature ◼Sizeof molecules diffusing ◼Type of molecules diffusing  Temperature ◼Warmer = Faster Size of Molecules ◼Smaller = faster ◼VIDEO When does Diffusion Stop? ◼ When equilibrium is reached –particles are evenly distributed –No gradient  What Molecules Move by Simple Diffusion? ◼Small molecules can pass easily through the cell membrane by simple diffusion. –Examples: Gases like O2 and CO2 Simple Diffusion  2 nd Type: Facilitated Diffusion ◼ Membrane Proteins facilitate (help) movement ◼ Molecules or ions enter or leave the cell moving down the concentration gradient. ◼ Theseprotein channels are specific for particular molecules – Example: only glucose molecules pass through glucose channels Facilitated Diffusion  What Substances move by Facilitated Diffusion? –Glucose – Sodium ions (Na+) –Chlorine ions (Cl-) –Potassium (K+) Facilitated Diffusion ◼ DOESFacilitated Diffusion REQUIRE ENERGY (ATP)???  3 rd Type: Osmosis ◼ Diffusion of WATER no energy required ◼ Occurs until equilibrium is reached ◼ Cytoplasm~ mostly water with dissolved solutes. ◼ Solutions with many solutes = less water Cytoplasm Composition  How does Water Move? ◼ Water moves from areas of HIGH water concentration to areas of LOW water concentration. OR ◼ LOW solute concentration to high solute concentration. ◼ Water moves towards high solute concentration. Osmosis Questions 1. What are the 3 types of passive transport? Questions 1. Which type of passive transport moves water across a semi-permeable membrane? 2. In what direction do materials move in passive transport? Use the phrase “concentration gradient”  Which type of transport uses Energy?  What is the source of energy in question #1?  When do molecules stop diffusing?  Which type of transport is used to transport the following materials: Water _____________ Ions _____________ Glucose ____________ CO2 ____________ Oxygen ____________  Solution Concentrations Effects of Osmosis on Cells Conditions cells can be found in….. ◼Hypertonic solutions ◼Hypotonic solutions ◼Isotonic solutions  Hypertonic Solutions ◼“Hyper” = over or above ◼ Solute concentration outside the cell is higher than inside the cell. ◼ Water diffuses out of the cell until equilibrium is reached. ◼ Animation  Hypertonic Solutions ◼ Non-plant Cells in Hypertonic Solutions usually DIE Result for a Plant Cell shrinks(Plasmolysis)! Chloroplasts “huddle up” ◼This causes wilting in plants.  Hypotonic Solutions ◼ “Hypo” = under or below ◼ The solute concentration outside the cell is lower than inside the cell ◼ Water diffuses into the cell Result: Cell Swells and bursts (cytolysis)! –Plant cells~ cell wall protects from bursting {Turgor pressure} ◼ Osmosis Animations for isotonic, hypertonic, and hypotonic solutions  Hypertonic vs. Hypotonic Hypertonic Hypotonic  Isotonic Solutions ◼ “Iso” = same ◼ The solute concentration outside and inside the cell are EQUAL ◼ Water diffuses into and out of the cell at Equal rates –there is NO Net Movement of Water. What type of solution are these cells in? A B C Animation  How Organisms Deal with Paramecium (protist) removing Osmotic Pressure excess water video Bacteria and plants’ cell walls prevent over-expanding. Pressure exerted on the cell wall in plants~ turgor pressure. Protists (paramecium) has contractile vacuoles collect pump water out to prevent over-expanding. Salt water fish pump salt out of their gills to prevent dehydration. Animal cells~ Kidneys keep the blood isotonic by removing excess salt and water. Questions ◼ Identify the following as Hypertonic, Hypotonic, or Isotonic: – Solute concentration is greater outside the cell. – Solute concentration is same inside and outside the cell. – Solute concentration is greater inside the cell. Questions ◼ Explain what happens when an animal cell is placed in a hypotonic solution. ◼ Explain what happens when a plant cell is placed in a hypotonic solution. Questions ◼ Explain what happens when an animal cell is placed in a hypertonic solution. ◼ Explain what happens when an animal or plant cell is placed in an isotonic solution. ◼ What feature in plants prevents them from bursting? Real Life Examples of Tonicity ◼ What would happen if you put a salt water fish in fresh water? Why ◼ What would happen if you put a fresh water fish in salt water? Why ◼ Why do you get thirsty after eating salty food? Explain.  Active Transport ◼ Movement Against a Concentration Gradient. (Low → High) ◼Requires energy (ATP)  Active Transport ◼ Usescarrier proteins –Cell Membrane Pumps –Use energy ATP  Active Transport ◼Important in maintaining ion concentration in cells and between cells. »Animation  Sodium Types of Active Transport Potassium Pumps (Active Transport using proteins) 1. Protein Pumps –ATP powered pumps that move ions and molecules from low to high Example: Nerve impulses. Protein changes shape to move molecules Notice the shape change of the pump Sodium-Potassium Pumps ◼ In Animals: important for muscle contractions and nerve impulses ◼InPlants: enables roots to absorb nutrients from the soil.  Types of Active Transport 2. Endocytosis: taking large amt of material into a cell Uses energy ‘Endo’ means ‘inside’ Brings large amt food Ex. WBC’s~ destroy bacteria by engulfing them!  2 Types of Endocytosis Phagocytosis Pinocytosis “cell eating” “cell drinking”  Types of Active Transport 3. Exocytosis: Forces material ‘out’ of cell Cell changes shape Requires ATP EX: Hormones or wastes released from cell Endocytosis & Exocytosis animations  Review of Cellular Transport Passive Transport Weeee!! ! -Does not use Energy 1. Diffusion 2. Facilitated Diffusion high 3. Osmosis low Active Transport This is -Uses Energy gonna be hard 1. Protein Pumps high work!! 2. Endocytosis 3. Exocytosis low  Questions ◼ List 2 similarities & 2 differences between Active and passive transport. ◼ Name the 3 types of active transport.  Questions ◼ Name the 3 types of passive transport. ◼ Provide 3 examples of how animals use active transport. ◼ What is the difference between exocytosis and endocytosis?  Problems with Cell Transport ◼ CF ◼ CF