Usually , rates of diffusion vary inversely with molecular weights; so smaller molecules diffuse faster than do larger ones. In cells, however, calcium ion diffuses more slowly than does cAMP. Propose a possible explanation.
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Usually , rates of diffusion vary inversely with molecular weights; so smaller molecules diffuse faster than do larger ones. In cells, however, calcium ion diffuses more slowly than does cAMP. Propose a possible explanation.
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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?Below find the structures for ibogaine and cocaine. Ibogaine and cocaine inhibit the dopamine active transporter (DAT). This transporter is a secondary active transporter, and depends on the primary active transporter Na+/K+ ATPase. Ibogaine had a Kι = 2 μM, and cocaine a Kι = 0.64 μM respectively. (a) Define secondary active transport. (b) Is ibogaine an effective treatment for cocaine based on DAT binding?Interpret the effect of hyperkalemia with reference to Goldman’s equation. a) What happens to rate of K+ diffusion at the MRP equilibrium with elevated extracellular [K+] (and unchanged intracellular [K+])?b) Since this diffusion rate determines the “permeability” of the cell to that K+ ion, what happens to PK+ as a result of this elevated extracellular K+? (Hint- it HAS changed.)c) Since PK+ has changed, and PNa+ is unchanged, what happens to the MRP as a result of this change in PK+? Explain with specific reference to Goldman’s equation but there is no need to cite or calculate any specific numbers, just generalize the result.
- Identify and explain two examples of diffusion you have experienced. Provide specific details in your explanation relating to the concept of diffusionPlease provide the mechanisms of the active transport of nano carriers used for crossing the blood brain barriers with detailed explanation and requirement needed to cross the blood brain barriers (what types of structures of the compounds, sizes). I want clear handwritten solution only....i will up voteHow much time would it take ATP to diffuse the following distances? (Use the equation for mean squared displacement in 1 dimension.) A. 1 µm (roughly the size of a bacterium) B. 6 µm (roughly the diameter of a T cell) C. 1 m (roughly the length of the axon of the sciatic nerve, which extends from the spinal cord to the big toe) D. Besides diffusion, what other mechanisms might a neuron use to transmit signals and transport molecules?
- If you made a hematocrit in two tubes. Tube A is made of 0.60M NaCl, and Tube B is made of 1.00M of NaCl, describe how the cell would respond in these solutions? Which would have a higher rate of osmosis? If the cell is permeable to NaCl, which would have a higher rate of diffusion?The contraction of cardiac muscle cells results from the increase in calcium ion levels in the cytosol. For the cells to relax, an antiport removes calcium ion from the cytosol for every sodium ion that is taken in. Digitalis is a drug that is used to make the heart contract more strongly. This drug partially inhibits the Na+-K+ ATPase in the cardiac cells. Applying the concepts about membrane transport, answer the following: a. Propose an explanation for the drug’s effect.b. What will likely happen if too much of the drug is taken in? Why?Dr Renko studied diffusion of tracer molecules to study paracellular diffusion across an epithelial monolayer of Caco-2 cells. The tracers were fluorescently labelled dextran molecules of different molecular weight. She is screening various drugs to determine whether they affect the cells in any way. Which drugs are most likely to change paracellular diffusion? a.) Drugs that modify microvilli are the most likely to change paracellular diffusion b.) Drugs that modify gap junctions are the most likely to change paracellular diffusion c.) Drugs that modify with aquaporins are the most likely to change paracellular diffusion d.) Drugs that modify tight junctions are the most likely to change paracellular diffusion
- Consider a solute having a permeability coefficient of 10-6 m s-1 for the plasma membrane of a cylindrical Chara cell that is 100 mm long and 1 mm in diameter. Assume that its concentration remains essentially uniform within the cell. Untitled Title A. How much time would it take for 90% of the solute to diffuse out into a large external solution initially devoid of that substance?* B. How much time would it take if diffusion occurred only at the two ends of the cell?* C. How would the times calculated in A and B change for 99% of the solute to diffuse out? D. How would the times change if Pj were 10-8 m s-1?*Chloride ions (Cl-) behave a bit differently to Na+ and K+ in that most cells don't have active Cl- transporters. As a result, the concentration gradient for Cl- is not 'set' like it is for Na+ and K+. There are, however, a limited number of Cl- leak channels in the cell membrane. As a result, Eci generally matches resting membrane potential - around - 70mV. Considering this, answer the following questions. If Cl- can cross the cell membrane, is not being actively transported, and membrane potential is -70mV, will there be a concentration gradient for Cl-?The contraction of cardiac muscle cells results from the increase in Ca?+ levels in the cytosol. For these cells to relax, an antiport removes Ca?+ from the cytosol for every Nat that is taken in. Digitalis is a drug that is used to make the heart contract more strongly. This drug partially inhibits the Na*-K* ATPase in the cardiac cells. Applying the concepts from membrane transport, answer the following: a. Propose an explanation for the drug's effect. b. What will likely happen if too much of the drug is taken in? Why do you say so?