Chapter 06 Lipids Membranes First Cells

1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 12) 13) 14) 15) 16) 17) A B B D A B B B D B B D B B B A B MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) Steroids such as cholesterol are an important component of animal cell membranes but do not actually form the membrane. Why? A) Lipids that form membranes are amphipathic with a polar region and a nonpolar region. B) The ring structure of steroids is too bulky to form a membrane. C) Steroids are too permeable to charged molecules to form a cell membrane. D) Steroids cannot interact with other molecules, which is required to form a cell membrane. 2) You make a phospholipid bilayer with short, saturated hydrocarbon tails. You measure the permeability of this membrane to oxygen. You then double the length of the hydrocarbon tails, and remeasure membrane permeability. You then double the length of the hydrocarbon tails again, and make a third measurement of membrane permeability. You graph membrane permeability as a function of hydrocarbon tail length. Which of the graphs below best represents the data you expect? A) B)   D) C)   3) You make a phospholipid bilayer with short, saturated hydrocarbon tails. You measure the permeability of this membrane to oxygen. You are going to change the length of the hydrocarbon tails and remeasure membrane permeability, but first your boss asks you to graph the data you expect if there is no effect of hydrocarbon tail length on membrane permeability (your null hypothesis). Which of the graphs below best represents the data you expect if your null hypothesis is correct? A) B)  C) D)  4) Phospholipids can form all of the following structures in water except which one? A) micelles B) bilayers C) vesicles 5) Cooking oil and gasoline (a hydrocarbon) are not amphipathic molecules. Why? A) They do not have a polar or charged region.   D) monolayers B) They do not have a hydrophobic region. C) They spontaneously form micelles or liposomes in solution. D) They are highly reduced molecules. 6) How do phospholipids interact with water molecules? A) Phospholipids dissolve in water. B) The polar heads interact with water; the nonpolar tails do not. C) The polar heads avoid water; the nonpolar tails attract water (because water is polar and opposites attract). D) Phospholipids don't interact with water because water is polar and lipids are nonpolar. 7) What do phospholipids and triglycerides have in common? A) They both have a phosphate. B) They both have a glycerol backbone. C) They both contain serine or some other organic compound. D) They both have three fatty acids. 8) In an experiment involving planar bilayers, a solution of table salt (sodium and chloride ions in water) is added on the left side of the membrane while pure water is added on the right side. After 30 minutes the researchers test for the presence of ions on each side of the membrane. The right side tests negative for ions. What can you conclude? A) The water somehow blocked the movement of ions across the membrane. B) Ions cannot cross planar bilayers. C) The left side would probably also test negative for ions. D) The experiment failed. 9) Which of the following is the best explanation for why vegetable oil is a liquid at room temperature while animal fats are solid? A) Vegetable oil has longer fattyacid tails than animal fats have. B) Vegetable oil has fewer double bonds than animal fats. C) Animal fats have no amphipathic character. D) Vegetable oil has more double bonds than animal fats. 10) Which aspect of phospholipids is most important to the formation of bilayers? A) Their hydrocarbon tails can consist of fatty acids or isoprene subunits. B) They are amphipathic. C) Their size is small, relative to fats. D) Their size is large, relative to cholesterol. 11) Which of the following crosses lipid bilayers the fastest? A) a sodium ion C) a small, polar molecule like water B) a small, nonpolar molecule like oxygen (O2) D) a large, polar molecule like glucose 12) Which of the following crosses lipid bilayers the slowest? A) a small, nonpolar molecule like oxygen (O2) B) a small, polar molecule like water C) a large, polar molecule like glucose D) a sodium ion 13) Steroid hormones are large communication molecules that are modified cholesterol molecules. How do you think they enter a cell? A) They must require a protein transporter, because the plasma membrane is completely impermeable to molecules. B) Their lipid nature probably allows them to diffuse through the plasma membrane. C) Their protein nature probably allows them to diffuse through the plasma membrane. D) Their size probably allows them to diffuse through the plasma membrane. 14) The text states that ribonucleotides can diffuse through some types of liposomes. It's likely that the lipids present early in chemical evolution had short chains. Would liposomes formed from these types of lipids be more or less permeable to ribonucleotides than if early cells formed from longchained lipids? A) less permeable B) more permeable C) same permeability 15) Where would you most likely find an integral membrane protein? A) floating freely in the cytoplasm B) spanning the cell membrane, with parts of the protein visible from both the inside and the outside of the cell C) on the inside surface of the cell membrane D) on the outside surface of the cell membrane 16) Which of the following means of transport would most likely be used for moving a mediumsized molecule (like a monosaccharide or an amino acid) from a low concentration on the outside of a cell to a high concentration on the inside of a cell? A) active transport through a "pump" protein B) passive transport C) facilitated diffusion through an ion channel protein D) facilitated diffusion through a transporter protein 17) Gramicidin is an antibiotic that increases the permeability of bacterial cell walls to inorganic ions. What is the most likely mode of action of gramicidin? A) It acts by active transport. B) It forms a channel in the membrane. C) It causes membranes to fuse with one another. D) It removes electrical charges from solutes.