Kranse et. al. measured the temperature dependence of conductance using membranescontaining the phospholipids glyceryl dipalmitate and glyceryl distearate. Describe themodifications in membrane content that you would employ to: (a) shift the temperature of the phase transition (b) make the ion conductance curve for valinomycin andnonactin more like that of gramicidin

Kranse et. al. measured the temperature dependence of conductance using membranescontaining the phospholipids glyceryl dipalmitate and glyceryl distearate. Describe themodifications in membrane content that you would employ to: (a) shift the temperature of the phase transition (b) make the ion conductance curve for valinomycin andnonactin more like that of gramicidin

Human Physiology: From Cells to Systems (MindTap Course List)

9th Edition

ISBN:9781285866932

Author:Lauralee Sherwood

Publisher:Lauralee Sherwood

Chapter3: The Plasma Membrane And Membrane Potential

Section: Chapter Questions

Problem 2SQE: One of the important uses of the Nernst equation is in describing the flow of ions across plasma...

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One of the important uses of the Nernst equation is in describing the flow of ions across plasma membranes. Ions move under the influence of two forces: the concentration gradient (given in electrical units by the Nernst equation) and the electrical gradient (given by the membrane voltage). This is summarized by Ohms law: Ix=Gx(VmEx) which describes the movement of ion x across the membrane. I is the current in amperes (A); G is the conductance, a measure of the permeability of x, in Siemens (S), which is I/V;Vm is the membrane voltage; and Ex is the equilibrium potential of ion x. Not only does this equation tell how large the current is, but it also tells what direction the current is flowing. By convention, a negative value of the current represents either a positive ion entering the cell or a negative ion leaving the cell. The opposite is true of a positive value of the current. a. Using the following information, calculate the magnitude of Na [ Na+ ]0=145mM,[ Na+ ]i=15mM,Gna+=1nS,Vm=70mV b. Is Na+ entering or leaving the cell? c. Is Na+ moving with or against the concentration gradient? Is it moving with or against the electrical gradient?
Using the Nernst equation, calculate the equilibrium potential for Ca2 and for C1 from the following sets of data: a. Given [ Ca2+ ]0=1mM,[ Ca2+ ]i=100nM, find Eca2+ b. Given [ Cl- ]0=110mM,[ Cl- ]i=100mM, find Ecl
Using the answer code on the right, indicate which membrane component is responsible for the function in question: 1. channel formation____________________________________ (a) lipid bilayer 2. barrier to passage of water- __________________ (b) proteins soluble substances ____________________________________ (c) carbohydrates 3. receptor sites 4. membrane fluidity 5. recognition of self 6. membrane-bound enzymes 7. structural boundary 8. carriers
Discuss why the following affect the rate of diffusion: molecular size, temperature, solution density, and the distance that must be traveled
Describe the contribution of each of the following to establishing and maintaining membrane potential: (a) the Na+K+ pump, (b) passive movement of K+ across the membrane, (c) passive movement of Na+ across the membrane, and (d) the large intracellular anions.
Using the ActiveModel for phosphofructokinase (Trypanosoma), describe the difference between the APO1, AP02, and holoenzyme conformations.
Assume that a membrane permeable to Na+ but not to Cl- separates two solutions. The concentration of sodium chloride on side 1 is higher than on side 2. Which of the following ionic movements would occur? a. Na+ would move until its concentration gradient is dissipated (until the concentration of Na+ on side 2 is the same as the concentration of Na+ on side 1). b. Cl- would move down its concentration gradient from side 1 to side 2. c. A membrane potential, negative on side 1, would develop. d. A membrane potential, positive on side 1, would develop. e. None of the preceding is correct.
THOUGHT QUESTION Imagine we identify a gene that is directly responsible for the effects of vasopressin on male mammals, including humans-we will call it trust1-that leads to the production of a vasopressin receptor in the brain, which we will call TRUST1. There are different versions of trust1, all of which lead to different levels of the behavior associated with this neuropeptide on male behavior. Give some examples where it would be a good idea to know a particular males genotype-that is, which of the trust1 genes he has. Give an example of when you think science has gone too far and this information should not be known.
The sodium/calcium exchanger (NCX) transports sodium into and calcium out of cardiac muscle cells. Describe why this transporter is classified as secondary active transport.
REFLECT AND APPLY Which statements are consistent with the known facts about membrane transport? (a) Active transport moves a substance from a region in which its concentration is lower to one in which its concentration is higher. (b) Transport does not involve any pores or channels in membranes. (c) Transport proteins may be involved in bringing substances into cells.
REFLECT AND APPLY Which statements are consistent with the fluid-mosaic model of membranes? (a) All membrane proteins are bound to the interior of the membrane. (b) Both proteins and lipids undergo transverse (flip-flop) diffusion from the inside to the outside of the membrane. (c) Some proteins and lipids undergo lateral diffusion along the inner or outer surface of the membrane. (d) Carbohydrates are covalently bonded to the outside of the membrane. (e) The term mosaic refers to the arrangement of the lipids alone.
Cells grown in the laboratory are mixed with a dye molecule that is unable to pass through the plasma membrane. If a ligand is added to the cells, observations show that the dye enters the cells. What type of receptor did the ligand bind to on the cell surface?