Membrane Structure and Function Guided Reading Questions to do before Mastering Biology Reading Chap 5 Intro 5 9 Reading Objectives Describe cell membrane structure Differentiate the kinds of molecules that can freely cross cell membranes vs those that can t Compare and contrast the different ways in which various substances cross membranes Make predictions about water movement during osmosis Q1 The chapter opener discusses aquaporins What is the function of these proteins To allow water to stream across cell membranes What if a person has too many in the membranes of their kidney cells Too much water would pass through the kidney and the body would not have enough water What if a person has too few in the membranes of their kidney cells Too little water would pass through the kidney and the body would have too much water 2 What is meant by the terms fluid mosaic and selective permeability when describing membranes Fluid Mosaic modern model of cell membrane structure like a mosaic of protein molecules in a fluid bilayer of phospholipid molecules Selective Permeability the property of regulating passage of substance across biological membranes in plasma membranes 3 Why was the spontaneous formation of membranes such an important step in cell evolution Then self replicating molecules could be passed on to daughter cells as new membrane enclosed vesicles bud off The basic requirement of life is a membrane that encloses an assembly of molecules and regulates chemical exchanges with the environment successfully 4 Use the words diffusion and concentration gradient in a sentence Diffusion is when particles spread out in available space according to the concentration gradient where the density of a chemical substance increases or decreases These concentration gradients are maintained by cells across their membranes 5 How does the structure of the membrane relate to its selective permeability Think about the chemical properties of the inner core of the bi layer The hydrophobic bilayer allows nonpolar molecules to easily pass through Ions and polar molecules must pass through concentration gradients and if they have transport proteins to help them cross What kinds of molecules can freely cross through passive transport without transport proteins Review and define the words polar and nonpolar if you need to Nonpolar molecules What kinds of molecules use facilitated diffusion a kind of passive transport that requires transporter proteins Polar molecules and ions including water 6 If I give you a 5 sucrose solution and a 10 sucrose solution in which is the water less concentrated The 10 sucrose solution 7 When water moves through a selectively permeable membrane down its concentration gradient this is termed osmosis 8 Is seawater hypertonic isotonic or hypotonic to drinking water hypertonic 9 If a hypotonic solution is put in a selectively permeable membrane and put into a hypertonic solution what will happen to the bag over time shrink or swell Why Where is the water more concentrated The bag will swell because it is gaining water and the water becomes mostly concentrated in the hypotonic solution 10 Water is a polar molecule and thus diffuses slowly into cells What type of membrane protein would you expect to find many of in a cell that must be highly permeable to water Transport proteins Aquaporin 11 Scientific Thinking in Module 5 7 Sometimes discovery is accidental What type of cell did Dr Agre s team accidentally discover aquaporins in Blood cells In their work shown in Figure 5 7 control frog eggs were compared to frog eggs that carried genetic information to make many aquaporins What result did they get when they put these two groups of eggs in a hypotonic situation describe Figure 5 7 The experimental eggs exploded in 3 minutes while the control eggs swelled minimally What did it tell them about the function of aquaporins This told them aquaporins allow for fast entry of water into the cells 12 In our discussion of how cells use glucose as an energy resource we will see that cells are continually bringing glucose in from the blood where the concentration is higher What kind of transport does glucose use Active transport 10 How do calcium ions move against their concentration gradient Through active transport because calcium is more concentrated outside of the cell 11 Compare and contrast exocytosis and endocytosis Exocytosis and endocytosis are both transport systems within the cell Exocytosis exports bulky items like proteins or polysaccharides out of the cell while endocytosis is when the cell take in larger molecules or fluid What are the distinctions between phagocytosis and receptor mediated endocytosis Phagocytosis is a type of endocytosis where the cell absorbs macromolecules other cells or particles into its cytoplasm while receptor mediated endocytosis requires the infoldings of vesicles with proteins and receptor sites specific to the molecules being taken in
View Full Document
Unlocking...