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TOPIC 8 Cell Membrane & Transport @ NSBHS KEY TERMS 1. Phospholipid 2. Fluid Mosaic Model 3. Selective Permeability 4. Passive Transport 5. Diffusion 6. Facilitated Diffusion 7. Osmosis 8. Active Transport 9. Endocytosis 10. Exocytosis LEARNING TARGETS… I will be able to… 1. Explain how both passive and active transport move materials across the cell membrane 2. Predict the impact to a plant or animal cell if placed in various types of solutions: a. Hypotonic b. Hypertonic c. Isotonic 3. Explain why cells are limited in size in terms of nutrient and waste transport 4. Create a model to simulate how a cell membrane works New Smyrna Beach High School 2014-15 TEXTBOOK Chapter 3, Cell Structure & Function Why is studying the cell membrane so important? Cell Membrane Diseases Cell membrane diseases are life-threatening disorders that are genetic in nature, and they usually work against proteins in our body that are key to ion channels and various receptors within the membrane. These diseases work by either disrupting the normal functions of the cells or by simply affecting the cell membrane. Many of these disorders contain other components as well. Hyaline Membrane Disease: Commonly associated with preterm infants, Hyaline membrane disease affects the lungs at the time of birth causing respiratory distress. As a result, the lungs require abnormal levels of oxygen & carbon dioxide exchange after birth. Alzheimer's Disease: The oxidative stress caused by Alzheimer's disease in the brain results in phospholipid altercations. Phospholipids are a key component of our cell membranes. These altercations compromise the cell membrane, therefore disrupting the function of the brain cells. Cystic Fibrosis: is a disease that brings about an excessive production of fluid in the lungs due to a defective calcium-ion channel. This channel contains a protein that is important to the cell membrane of our lungs. The channel controls the level of fluids and mucus in our lungs. When this channel mutates into cystic fibrosis, it causes the mucus to build up in the lungs, thus making it hard to breath. Duchenne Muscular Dystrophy: This disease affects dystrophin in the muscle cell. Dystrophin allows the muscle cell wall to connect with the intracellular section. In the absence of dystrophin, the CM would be incapable of repairing itself, destroying it & bringing about MD. How Muscle Cells Seal Their Membranes ScienceDaily (Mar. 14, 2012) — Every cell is enclosed by a thin double layer of lipids that separates the distinct internal environment of the cell from the extracellular space. Damage to this lipid bilayer, also referred to as plasma membrane, disturbs the cellular functions and may lead to the death of the cell. For example, exercise like downhill walking tears many little holes into the plasma membranes of the muscle cells in our legs. To prevent irreparable damage, muscle cells have efficient systems to these holes again. With a laser, the researchers burned tiny holes into the plasma membrane of muscle cells and followed the repair of the holes under the microscope. They showed that membrane vesicles together with two proteins Dysferlin and Annexin A6 rapidly form a repair patch. Researchers at Karlsruhe Institute of Technology (KIT) and Heidelberg University have succeeded for the first time in observing membrane repair in real-time in a living organism. Researchers suggest that the cell assembles a multilayered repair patch from the inside that seals off the cell's interior from the extracellular environment. It was also found that there is a specialized membrane area that supplies rapidly the membrane that is needed for sealing the plasma membrane hole. The results may contribute to the development of therapies for human myopathies (muscular diseases) and open up new possibilities in biotechnology. Chemists Synthesize Artificial Cell Membrane ScienceDaily (Jan. 26, 2012) — Chemists have taken an important step in making artificial life forms from scratch. Using a novel chemical reaction, they have created self-assembling cell membranes, the structural envelopes that contain and support the reactions required for life. "One of our long term, very ambitious goals is to try to make an artificial cell, a synthetic living unit from the bottom up -- to make a living organism from non-living molecules that have never been through or touched a living organism," Devaraj, an assistant professor at UCSB said. "Presumably this occurred at some point in the past. Otherwise life wouldn't exist." By assembling an essential component of earthly life with no biological precursors, they hope to illuminate life's origins. Nature uses complex enzymes that are themselves embedded in membranes to accomplish this, making it hard to understand how the very first membranes came to be. They created the synthetic membranes from a watery emulsion of an oil and a detergent. Alone it's stable. Add copper ions and sturdy vesicles and tubules begin to bud off the oil droplets. After 24 hours, the oil droplets are gone, "consumed" by the self-assembling membranes. Mechanism of Sculpting the Plasma Membrane of Intestinal Cells Identified ScienceDaily (Aug. 2, 2011) — The research group of Professor Pekka Lappalainen at the Institute of Biotechnology, University of Helsinki, has identified a previously unknown mechanism which modifies the structure of plasma membranes in intestinal epithelial cells. Typically, modifier proteins serving the cell typically twist the cell membrane into pipe-like, concave or convex structures. The parts protruding and drawn in like this are vital for cell movement, shape transformation and nutrient intake. Unlike other proteins with a similar function, the new protein -- named 'Pinkbar' -- creates planar (flat) membrane sheets. Further research investigates the potential connection of this protein with various intestinal disorders. A dynamic plasma membrane surrounds all eukaryotic cells. Membrane plasticity is essential for a number of cellular processes; changes in the structure of the plasma membrane enable cell migration, cell division, intake of nutrients and many neurobiological and immunological events. Earlier research has shown that certain membrane-binding proteins can 'sculpt' the membrane to generate tubular structures with positive or negative curvature, and consequently induce the formation of protrusions or invaginations on the surface of the cell. These membrane-sculpting proteins are involved in various vital cellular processes and can control the shape of the plasma membrane with surprising precision. Many of the membrane proteins have also been linked to severe diseases such as cancer and neurological 2 syndromes. In humans, Pinkbar is only found in intestinal epithelial cells where it may be involved in the regulation of intestinal permeability. In the future, it will be important to identify the exact physiological function of Pinkbar in intestinal epithelial cells and to study the possible links of this protein to various intestinal disorders Concept Map Types of Cell Transport Directions: Given the following terms, complete the Concept map showing how these words are related. Use the definitions on the screen for help: Active transport, Endocytosis, Diffusion, Facilitated diffusion, Passive Transport, Osmosis, Exocytosis, Pinocytosis, Phagocytosis, Transport through Cells 1. 2. 3. 4. 6. 5. 7. 8. 9. 10. 3 Transport Into and Out of the Cell DIFFUSION, OSMOSIS & THE CELL MEMBRANE Underline/Highlight the answers to the questions within the article 1. What is the relationship between transport & the Cell Membrane? All living things have certain requirements they must satisfy in order to remain alive. These include exchanging gases (usually CO2 & O2), taking in water, minerals, & food, & eliminating wastes. These tasks occur at the cellular level, & require that molecules move through the plasma/cell membrane that surrounds the cell. This membrane is a complex structure that is responsible for separating the contents of the cell from its surroundings, for controlling the transport of materials into & out of the cell, & for interacting with the environment surrounding the cell. 2. What is Selective Permeability & how does it relate to homeostasis? The membrane selects or chooses the materials it wants to pass into or out of the cell. This is referred to selective permeability or the membrane being selectively permeable. The membrane will ‘choose’ to let the ‘good stuff’ in and keep the ‘bad stuff’ out or vice versa. Because it does so, it maintains stability or homeostasis in the cell. 2 METHODS OF MOLECULE MOVEMENT in & out of the cell Passive and Active Transport 3. How is PASSIVE TRANSPORT like “taking the easy road”? 1. PASSIVE TRANSPORT does NOT require energy expenditure, spontaneous! ________________________________________________________________________ ACTIVE TRANSPORT requires that the cell use energy that it has obtained from food to move the molecules (or larger particles) through the cell membrane. Passive transport does not require energy & work. There are several different types of this easy movement of molecules—the two major ones are Diffusion & Osmosis. 4. What is DIFFUSION? The principle type of passive transport is diffusion. DIFFUSION is the movement of molecules from an area in which they are highly concentrated to a area in which they are less concentrated; like spraying perfume in an enclosed room. When the molecules are even throughout a space - it is called equilibrium. 5. Draw the next 4 boxes showing how the molecules will move throughout the space until it finally reaches equilibrium. 6. Why do you think that equilibrium inside the cells is important? _____________________________________________________________________ _____________________________________________________________________ 4 Passive Transport, Continued... 7. What is OSMOSIS? A second type of Passive Transport is Osmosis. OSMOSIS is the diffusion of water—and water ONLY—(across a membrane) from a higher concentration to a lower concentration. · Osmosis is a water specific process!! For a cell to survive, concentrations of many substances need to be the same on both sides of the cell membrane. If the cell does not pump out all of its extra ions, for example, to even out the concentrations, the water is going to move in. This can be very bad. The cell can swell up and explode. The classic example of this type of swelling happens when red blood cells are placed in water. The water rushes in to the cells, they expand and eventually rupture! In the picture to the right, osmosis is taking place: the water molecules are moving across a selectively permeable membrane. Water molecules are the small shapes, and the solute (solid particle) is the bigger circles. Solute = _______________________________________ Solvent = ______________________________________ 8. In the diagram at the right, color the water molecules blue and the sugar molecules pink. 9. Since Osmosis is water moving from HIGH to LOW amounts, indicate with an arrow which direction the water is moving in the picture. 5 Passive Transport ,Continued... THREE TYPES OF SOLUTIONS "ISO" means the same —> An isotonic solution is one in which the amount (concentration) of solute (salt) is equal on both sides, the water in the solution will move back in forth but it won't have any result on the overall amount of water on either side. EX: HypOtonic HYPO" means less, in this case there are less solute (salt) molecules outside the cell, since salt sucks, water will move into a cell 11. What happens to plant cells when water fills the vacuole? What happens to animal cells when water fills the cell? When water from the solution moves into the cell. The cell will gain water and grow larger. In plant cells, the central vacuoles will fill and the plant becomes stiff and rigid, the cell wall keeps the plant from bursting. This pressure is called _________________ In animal cells, the cell may be in danger of bursting; organelles called contractile vacuoles will pump water out of the cell to prevent this. EX: ISOtonic 10. In an ISOtonic solution, indicate with an arrow, which way the water moving? 12. In a hypotonic solution, indicate with an arrow which way the water is moving? EX: Hypertonic 13. What happens to plant cells when water is lost? What about animal cells? 14. In a hypertonic solution, indicate with an arrow which way the water moving? The word “HYPer” means more. In this case. There are more solute (salt) molecules outside the cell, which causes the water to be sucked out of the cell In plant cells, the central vacuole would lose water and shrink, causing wilting. In animal cells, the cells shrink. In both cases, the cell may die…. That is why it is dangerous to drink sea water – it is a myth that drinking sea water will case you to go insane, but people marooned at sea will speed up hydration (& death) by drinking sea water – SALTS SUCKS! — That is also why “salting fields” was a common tactic during war, it would kill the crops in the field, thus causing food shortages. 6 Active Transport 15. How is ACTIVE TRANSPORT like “Taking the Hard Road”? 16. EX. of Active Transport = The Sodium Potassium Pump Active transport requires that the cell use energy, because substances are moving against the concentration gradient. It is the opposite from passive transport in that the amount of material moves from a low amount to a high amount – like going UPHILL, instead of downhill. The liquids inside and outside of cells have different substances. Sometimes a cell has to work and use some energy to maintain a proper balance of molecules. Process that maintains balance of sodium inside cell and potassium outside of cell; both substances are moving against the gradient (uphill) which requires ATP (energy) Active transport usually happens across the cell membrane. There are thousands of proteins embedded in the cell's lipid bilayer. Those transport proteins do much of the work in active transport. They are positioned to cross the membrane so one part is on the inside of the cell and one part is on the outside. The membrane proteins are very specific. One protein that moves glucose will not move calcium (Ca) ions. There are hundreds of these membrane proteins in the many cells of your body. Many times, proteins have to work against a concentration gradient. That term means they are pumping something (usually ions) from areas of lower to higher concentration…. Like going UPHILL. This happens a lot in neurons (nerve cells). The membrane proteins are constantly pumping ions in and out to get the membrane of the neuron ready to transmit electrical impulses. 17. Highlight the arrows – why are particles moving back and forth??? 18. EX. of Active Transport = Proteins in the Membrane Protein channels 19. Color the Protein Channels purple. 7 Active Transport, continued... 20. EX: ENDOcytosis Process by which the cell takes in / out? large particles by engulfing them 21. EX: EXOcytosis Process by which the cell gets rid of particles; opposite of _______cytosis. Even though proteins are working to keep the cell alive, their activity can be stopped. There are poisons that stop the membrane proteins from transporting their molecules. Those poisons are called inhibitors. Sometimes the proteins are destroyed and other times they are just plugged up. Imagine that you are a cell and have ten proteins working to pump calcium into the cell. What if a poison came along and blocked eight of them? You could not survive with just two pumps working and would slowly die. It would be like expecting you to breathe with your mouth and nose plugged up! Dynamic equilibrium occurs when 2 opposing actions occur at the same rate. 22. Label the part of the diagram showing Endocytosis AND Exocytosis 23. LOOK at the diagram: What kind of particles would you want your body to get rid of? What kind of particles would your body WANT to engulf? 24. Why is it important to know what Inhibitors do 25. Why is it better for cells to be in equilibrium? If you were to poke a hole in the bottom of the bucket, water would leak out. This system would not be at equilibrium because there is action taking place water is leaking out - and the water level in the bucket would drop. However, if you were to begin pouring water into the bucket at the same rate that it was leaking out, the water level in the bucket would stay the same because the rate at which the water is entering the bucket is equal to the rate at which it is leaking out. This is an example of dynamic equilibrium. It means the cell is healthy! 8