BIOL 1406 Discussion Questions Membranes and Cell Transport 1 The membranes of winter wheat become more fluid when they a increase the percentage of unsaturated phospholipids in the membrane b increase the percentage of cholesterol molecules in the membrane c decrease the number of hydrophobic proteins in the membrane 2 If a blood research laboratory is attempting to collect the content of human red blood cells researchers should use what type of solution to cause blood cell lysis 3 Use the diagram below to answer questions a c a Which beaker s contain s a solution that is hypertonic to the bag b Which bag would you predict to show the least change in mass at the end of the experiment c Arrange the beakers in order of the mass of the bags inside them after the experiment has run for 30 minutes List the bag that loses the most mass first 4 Pickles may be preserved in brine which is a 30 salt solution How does this method of preservation prevent contamination by microorganisms 5 Glucose is a six carbon sugar that diffuses slowly through artificial membranes The cells lining the small intestine however rapidly move glucose from the gut into their cytoplasm This occurs whether the gut concentrations of glucose are higher or lower than the glucose concentrations in intestinal cell cytoplasm Using this information which transport mechanism is most likely responsible for the glucose transport in intestinal cells Why 6 Consider the transport of protons and sucrose into a plant cell by the sucrose proton cotransport protein Plant cells continuously produce a proton gradient by using the energy of ATP hydrolysis to pump protons out of the cell Why in the absence of sucrose don t protons move back into the cell through the sucrose proton cotransport protein 7 While on a trip to the desert a friend of yours was bitten by a rattlesnake He nearly died from hemolysis or breakage of many of his red blood cells You have analyzed the snake venom and found three enzymes phospholipase which degrades phospholipids neuraminidase which removes cell surface carbohydrates and protease which degrades proteins Which of these enzymes do you think was responsible for his near fatal red blood cell hemolysis Why Question adapted from The Biology Project 8 If a cell membrane were composed of only a phospholipid bilayer what properties would it have 9 Ethanol the active ingredient in alcoholic beverages is a small polar and uncharged molecule Would you predict that this molecule crosses cell membranes quickly or slowly Explain your reasoning 10 What functions might each of the three types of diffusion serve in an independent cell like a Paramecium or an amoeba in a multicellular organism for example a human or a tree 11 Would you expect an amoeba that lives in a pond in a cold northern climate to have a higher or lower percentage of saturated fatty acids in its membranes during the summer as compared to the winter Explain your answer 12 When biomedical researchers design drugs that must enter cells to be effective they sometimes add methyl CH3 groups to make the drug molecules more likely to pass through cell membranes Conversely when researchers design drugs that act on the exterior of cell membranes they sometimes add a charged group to decrease the likelihood that the drugs will pass through membranes and enter cells Explain why these strategies make sense 13 Some elements can pass through the lipid bilayer rather quickly while others take some time Of the following which would move through the lipid bilayer of a plasma membrane most rapidly Why CO2 an amino acid glucose K starch 14 One function of membrane proteins is transportation of substances across the membrane If a cell biologist placed cells into an environment with a chemical that blocks the function of these transport proteins which processes will be blocked 15 One day during the summer you and some friends made ice cream using an electric ice cream maker A few days later you noticed a yellow circle of dead grass where the ice cream freeze had been placed What happened 16 A laboratory assistant prepared solutions of 0 8 M 0 6 M 0 4 M and 0 2 M sucrose but forgot to label them After realizing the error the assistant randomly labeled the flasks containing these four unknown solutions as flask A flask B flask C and flask D Design an experiment based on the principles of diffusion and osmosis that the assistant could use to determine which of the flasks contains each of the four unknown solutions Include in your answer a a description of how you would set up and perform the experiment b the results you would expect from your experiment and c an explanation of those results based on the principles involved 17 An artificial cell consisting of an aqueous solution enclosed in a selectively permeable membrane has just been immersed in a beaker containing a different solution The membrane is permeable to water and to the simple sugars glucose and fructose but completely impermeable to the disaccharide sucrose a Which solute s will exhibit a net diffusion into the cell b Which solute s will exhibit a net diffusion out of the cell c Which solution is hypertonic to the other d In which direction will there be a net osmotic movement of water 18 Diagram and describe the structure of a phospholipid molecule 19 Explain what happens when a group of phospholipid molecules are placed in water 20 Draw a diagram of the fluid mosaic model of membrane structure and label the following parts phospholipid cholesterol transmembrane protein peripheral protein glycolipid glycoprotein filaments of cytoskeleton 21 Describe the process of diffusion 22 What types of substances can pass through cell membranes by simple diffusion and what types of substances cannot 23 What is facilitated diffusion 24 How is facilitated diffusion similar to simple diffusion How are they different 25 How are carrier proteins similar to channel proteins How are they different 26 Describe the process of osmosis 27 What happens when a cell is placed in a hypotonic solution Explain why 28 What happens when a cell is placed in a hypertonic solution Explain why 29 What happens when a cell is placed in an isotonic solution Explain why 30 Describe 3 different methods that organisms have evolved to maintain osmotic balance with their environment 31 Explain the difference between passive transport and active transport 32 Indicate which of the following transport mechanisms are active and which are passive