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2009 Fall Bio 328 Exam 1

2009 Fall Bio 328 Exam 1 - FOR EACH QUESTION SELECT THE...

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FOR EACH QUESTION, SELECT THE MOST INCORRECT ANSWER Mark your answers on the op-scan sheet with a No.2 pencil. If you change your answer, be sure to erase thoroughly. There are 20 questions on this examination so be sure to answer all of them. Fill in your name and SBU ID number (NOT YOUR SS#) on the answer sheet. ___________________________________________________________________________________ 1. Membrane Potential a. The primary current carriers in biological systems are ions in solution. b. Intracellular fluids have a relatively high concentration of sodium ions. c. Ions in solution are surrounded by a tight shell of water molecules known as a hydration shell. d. Negatively charged ions are called anions. e. Ohm’s Law can be used to describe the movement of ions through ion channels. 2. Membrane Potential a. Assuming that Cl- ions make a negligible contribution to setting the membrane potential, if, [K + ] i = 125 mM, [K + ] o = 5 mM, [Na + ] i = 12 mM and [Na + ] o = 120 mM and the membrane is 50 times more permeable to K+ ions than to Na+ ions the membrane potential will be approximately –71 mV. b. According to Ohm’s law, if the membrane potential is –70 mV the K+ current will be an inward current, assuming normal external and internal K+ ion concentrations. c. The Goldman equation gives the relationship between the membrane potential and the ion concentrations and ion permeabilities for permeant ions. d. The equilibrium potential for a potassium ion, which has an internal concentration of 200 mM and an external one of 2 mM, is exactly -116 mV. e. An ion is at electrochemical equilibrium when its electrical potential is equal and opposite to its chemical potential. 3. Membrane Potential a. The electrical potential inside a mammalian cell is negative with respect to the outside of the cell. b. Separation of charged ions across the capacitance of the cell membrane produces the resting membrane potential. c. The principle of electroneutrality states that there are an equal number of positive and negative charges in the bulk solutions inside and outside of the cell. d. The membrane potential of a cell is the difference between the intracellular electrical potential and the extracellular one. e. Membrane pumps produce a separation of charge across the cell membrane by pumping cations out of the cell and anions into the cell.
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4. Cell Physiology a. The intracellular calcium concentration is 2 mM. b. Transporters are needed for polar or charged molecules to cross cell membranes. c. The energy necessary for facilitated transport is provided by the chemical concentration gradients of the transported molecules. d. Membrane pumps use the chemical energy derived from the hydrolysis of ATP. e. Facilitated diffusion is so called because the transporter simply facilitates the diffusion of a solute across the membrane down its concentration gradient.
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2009 Fall Bio 328 Exam 1 - FOR EACH QUESTION SELECT THE...

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