D103 Midterm 1 with well explained questions and answers.

D103 Midterm 1 with well explained questions and answers. Which factors are likely to lead to a decrease in membrane fluidity? A: An increase in the number of unsaturated bonds in the hydrophobic tail of phospholipids B: An increase in the activity of a transmembrane protein C: A change in the molar ratio of PC to PE D: An increase in the number of phospholipids with long hydrophobic tails - correct answers.D Which of the following organisms is most likely to have the highest percentage of unsaturated fatty acid chains in their membranes? A: Antarctic bacterium B: Desert iguana C: Human being D: Polar bear E: Thermophilic bacterium - correct answers.A Why is cholesterol able to integrate into a lipid bilayer? A: Because it is a small molecule B: Because it is a fully hydrophobic molecule C: Because it is abundant D: Because it has an amphipathic organization, similar to membrane lipids E: Because it can bind covalently to phospholipids - correct answers.D Which of the following statement best describes how bacteria in a hot spring control the fluidity of their plasma membrane? A: They decrease the percentage of lipids with unsaturated fatty acid tails in their plasma membrane B: Because they don't synthesize cholesterol, they cannot control membrane fluidity and therefore have a very fluid plasma membrane. C: They reduce cholesterol production to prevent membranes from becoming too fluid. D: They form lipid rafts in their membranes to prevent too much fluidity E: They increase the percentage of lipids with unsaturated fatty acid tails in their plasma membrane - correct answers.E Which information can you obtain from a hydrophobicity plot? A: The number of potential hydrophobic transmembrane domain B: The topology of the protein C: Where the protein localizes in the cell D: Its interaction partner E: The protein's function - correct answers.A Imagine a small synthetic vesicle made from pure phospholipids (formed as lipid bilayer). Its lumen contains 1 mM Glucose and 1 mM sodium chloride (NaCl). If the vesicle is placed in pure water, which of the following happens the fastest? A: Na+ diffused out B: Cl- diffused out C: H2O diffused in D: Glucose diffused out E: Nothing happens - correct answers.C In contrast to transporters, channel proteins in cellular membrane: A: Undergo a conformational change every time they transport an ion solute B: Can only mediate passive transport C: Form pores that are always open D: Are always controlled by voltage - correct answers.B Which of the following molecules is most likely to induce a conformational change in a uniporter that transports glucose across the plasma membrane? A: An extracellular ligand B: An intracellular ligand C: There is no need for a ligand, as the transporter changes conformation spontaneously D: A molecule of glucose E: A Na+ ion - correct answers.D