Sci 10 Unit C.2.pdf

Science 10 & Cellular Transport C 2.1-2.4  The Cell Membrane as a Gate Keeper The cell is an open system, which means that it allows for the exchange of matter and energy between itself and its surrounding. This exchange is, however, regulated by the cell membrane, which selects what...

Science 10 & Cellular Transport C 2.1-2.4  The Cell Membrane as a Gate Keeper The cell is an open system, which means that it allows for the exchange of matter and energy between itself and its surrounding. This exchange is, however, regulated by the cell membrane, which selects what is allowed to move in and out. The function of this selective permeability is to maintain equilibrium, homeostasis, or balance inside the cell.  Cell Membrane Structure: The Fluid Mosaic Model The cell membrane, also referred to as the plasma membrane, consists of a phospholipid bilayer. That is to say that is has a double layer of lipids (fats), each having a phosphate group attached on either surface of the membrane. Interspersed in this membrane are proteins. Some of which have sugar molecules (carbohydrates) attached to them.  Forms of Cellular Transport The components and structure of the cell membrane allow for the exchange of materials between the cell and its surroundings via a number of different methods. Some of these methods, collectively called passive transport, occur using only the kinetic energy of molecules involved. Other methods, collectively referred to as active transport, require the input of additional energy, provided by a molecule called ATP, produced through cellular respiration.  Energy and Concentration Gradients The difference in energy requirements has to do with the concentration of molecules inside, as compared to outside, the cell. A difference in concentration of molecules is called a concentration gradient. No extra energy (ATP) is required to move molecules down (with) a gradient; from an area of high to low concentration. Energy is required to move molecules up (against) a gradient; from an area of low to high concentration.  Types of Passive Transport 1. Diffusion is the spontaneous movement of particles from an area of higher concentration to an area of lower concentration. Diffusion continues until all particles are evenly spread out; are in equilibrium. Rate of diffusion can be increased by adding energy and increasing molecular movement. (heating or stirring)  Diffusion & The Particle Model of Matter The occurrence of diffusion is commonly explained using the particle model of matter that states that: S – large spaces exist between the particles of matter. A – attractive forces are found between particles. These forces are most significant for solids and least for gases. M –particles are in constant motion. With motion being the most significant for gases and the least for solids  2. Osmosis Osmosis is the diffusion of water across a membrane that is permeable to water, but not the solute (semi-permeable). Demo Act. C8 p.276: starch and iodine diffusion across a semi- permeable membrane.  Osmosis & Cell Tonicity Tonicity refers to the concentration of a solution in comparison to that of another. Knowledge of the tonicity of a solution in comparison to that of a cell allows to predict the direction of water movement Isotonic = same as cell Hypotonic = less solute than cell Hypertonic = more solute than cell Demo: The Incredible Egg Lab p.280 Refer to video  Use p.279 Skill Practice as a basis for students to determine why vegetables become crispy when place in a container of water. Assign workbook p. 179-181  3. Facilitated Diffusion Due to the lipid nature of cell membranes, only fat soluble substance move freely across membranes. Water soluble substance need assistance in the form of a protein channel or carrier protein in order to move across the cell membrane. Facilitate diffusion is still the movement from higher to lower concentration, but with proteins facilitating the movement.  Types of Active Transport 1. Active Transport with Carrier Proteins Similar to facilitated diffusion, but requiring energy to move molecules from a low to a high concentration. May bring needed entities into the cell or expel materials from the cell.  2. Endocytosis & Exocytosis Essentially the reverse processes of one another, endocytosis and exocytosis often involve molecules that are too large to be transported across the cell membrane by carrier proteins. Both endocytosis and exocytosis require energy from ATP for vesicle formation the rearrangement of the cell membrane.  Types of Endocytosis: Phagocytosis and Pinocytosis Phagocytosis involves the intake of larger molecules, while pinocytosis is the engulfment of liquid and dissolved molecules. § Youtube videos: § Cellular Transport § Membranes and Transport § Cell Membranes Rap § Assign workbook p.182-183 #18-23 § Have students complete a flow chart or other graphic organizer that summarizes the transport of materials across a membrane. (Can be adding details to p.183 #23) § Computer Simulations and Activities as per next slide. § Crossword Puzzle § Cell Transport Review Worksheet § More: Check and Reflect Questions p.283 #7-9  Internet Activities § Cellular Transport computer simulations and interactive sites 1)http://www.sumanasinc.com/webcontent/animations/biology.html (For diffusion – active transport) 2) https://www.blinn.edu/natscience/Biology_Tutorials.html (Scroll to osmosis and diffusion section and select phagocytosis and pinocytosis) 3) https://www.quia.com/quiz/1610803.html (Online quiz)  C 2.3 Applications of Cellular Transport in Industry and Medicine Knowledge of the cell membrane and cellular transportation has application in both industry and medicine. Synthetic membranes are being developed to mimic natural functions. § Jig-saw activity § Form groups of at least 5 students (Each member is assigned a number from 1-5) § All #1’s meet together (as well as #2’s, #3’s etc) (they will become the “expert group” for their assigned section) § Each group is responsible for one of the subtopics (Membrane Proteins and Disease; Synthetic Membrane Technology; Transport of Protein Hormones; Peritoneal Dialysis; Reverse Osmosis) § Fill in their appropriate boxes on Applications of Membrane Technology handout with Key ideas from p.224-288 Readings. § Return to their original group to report their findings and summary of their section § All other members now will fill in the rest of their handout. § Supplemental video material on: membrane technology and hemodialysis & peritoneal dialysis § Assign Check and Reflect p.288. #1,2,4-6  Surface Area to Volume Ratio and the Development of Specialized Structures. Diffusion occurs more rapidly into a structure if the structure has a large surface area for its volume. Specialized structures in organisms that are used to increase diffusion by increasing the SA:V ratio include: Leaves, especially those that are flat. Tiny hair-like extensions on roots, called root hairs Finger-like projections in the human digestive tract, called villi Small sacs in the lungs, called alveoli Capillaries, which carry blood throughout the body Without an adequate SA:V ratio, organisms may not be able to get the nutrition they need within the time frame required and/or wastes may build up. Either situation can reduce function, and may lead to death. Calculating Surface Area: Volume Ratio Lab to compare the SA: V ratio with the rate of diffusion. * Show Video Review questions text p.289 #1 & 2, p.293 omit #1 & 4, p.294 #16 WB p.184-185 Section Review p.294-295 #2,6-8,10,16, 19-22,26,31,32, 35