MCB 2210 SPRING 2015 PROBLEM SET 2 1 Molecules that are and will pass through the lipid bilayer a small hydrophilic most easily b small hydrophobic most easily c large hydrophobic least easily d large hydrophilic least easily e b and d are both correct 2 Which is most directly responsible for determining the value of the resting potential of neurons and other cells a Voltage gated Na channels b the Na K ATPase c K channels d the Na H exchanger e none of the above 3 The K ion channel is a trans membrane protein complex that transports K ions across the plasma membrane What description of the protein is likely to be true a Most of the hydrophilic amino acids will face toward the pore channel b Most of the hydrophobic amino acids in the transmembrane alpha helixes will interact with the lipid portion of the membrane c The protein is likely to contain multiple amphipathic alpha helices d The protein will be glycosylated e all of the above 4 A cell with the standard ECF and ICF composition with a membrane potential of 75mV will experience a change in membrane potential if which of the following conductances is changed a K b Na c Ca2 d a and c e all of the above 5 An ion is found at higher concentrations inside of cells than outside What mechanism could result in this accumulation a Movement through a channel b Active transport c Because the ion is small it will likely diffuse directly through the lipid bilayer d a and b are correct e All of the above 6 Which of the statements a b c regarding the equilibrium distribution of solutes across membranes is false a The equilibrium distribution of a charged molecule across a membrane depends on the chemical gradient concentration and on the electrical gradient membrane potential b Uncharged molecules are not sensitive to membrane potentials so they will be at equilibrium only when at the same concentration on both sides of the membrane c Charged molecules can be at equilibrium even if the concentration inside and outside are different d both a and b are false e All are true 7 Lysosomal membranes contain a proton pump that utilizes the energy of ATP hydrolysis to pump protons into the lysosome thereby maintaining the lumen at a low pH Which statement is correct a This is an example of secondary active transport b This is an example of primary active transport c This is an example of passive transport d This is an example of a symporter e This is an example of an antiporter 8 Suppose you were to treat a normal mammalian cell with a substance that inhibits the Na K ATPase Would be the most immediate effect upon the cell a There would initially be very little change b The cell s osmotic balance would immediately be disrupted and the cell would swell and explode c The cell membrane potential would immediately drop to zero d The cell would very quickly run out of ATP e The cell if it were excitable would immediately be unable to create an action potential 9 The Na Glucose cotransporter can bring glucose into the cell when there is more glucose inside than outside The energy input needed to drive the transport comes a Directly from ATP cleavage b From the Na gradient c From the glucose gradient d From simple diffusion e From phosphorylation of the transporter 10 In a standard cell under standard ionic conditions if the membrane potential is 75 mV which statement about current flows is correct a Na is flowing into the cell b K is flowing out of the cell c The net current carried by Na and K is zero d The Na K ATPase must act to keep the ionic gradients from changing e All are true statements 11 The type of membrane transport that uses ATP as the direct energy source is a facilitated diffusion b passive transport c primary active transport d secondary active transport e simple diffusion 12 In the cotransport of glucose and sodium ions a Glucose molecules are transported up their concentration gradient b Sodium ions are transported up their concentration gradient c The transport of glucose powers the transport of sodium d ATP causes a conformational change in the carrier protein e An antiporter is involved 13 Which statement is false regarding carrier and channel membrane transport proteins a Carrier proteins have to undergo larger shape changes to transport solutes than channels do b An individual transported ion remains associated with a channel for a much longer time than an individual solute remains associated with a carrier protein c For transport to work all gates on an ion channel must be open whereas for a carrier to work at least one gate must always be closed d a and b are false e All statements are false 14 Consider a typical cell with the standard ECF and ICF membrane potential of 75 mV If the Lecture 3 Slide 17 ECF ICF conditions sodium conductance decreases a The membrane potential will become more negative b The membrane potential will become more positive c There will be no change in the membrane potential d Cannot be determined from the information given e None of the above Compare membrane potential to the substance s charge If a POSITIVE substance increases decreases the membrane potential becomes more positive negative If a NEGATIVE substance increases decreases the membrane potential becomes more negative positive 15 Consider a typical cell with the standard ECF and ICF membrane potential of 75 mV If the potassium conductance decreases Na moves in a The membrane potential will become more negative K moves out b The membrane potential will become more positive c There will be no change in membrane potential d Cannot be determined from the information given Less positive charge is moving out therefore potential is more positive 16 Consider a typical cell with the standard ECF and ICF membrane potential of 75 mV If the extracellular concentration of K increases dramatically a The membrane potential will become more negative b The membrane potential will become more positive c There will be no change in the membrane potential d The Nernst potential for K would change e b and d are correct More positive charge outside so the membrane potential is more positive 17 Which is true about chaperones a Chaperones protect cells from heat stress b Chaperones help fold proteins into proper conformations c Chaperones use ATP to help fold proteins d All of the above are true about chaperones e None is true 18 Which of the following increase bilayer thickness a Phospholipids with long saturated fatty acyl chains b Phospholipids with short