In the situations described below, what is the free energy change if 1 mole ofNa* is transported across a membrane from a region where the concentra-tion is 1 µM to a region where it is 100 mM? (Assume T = 37 °C.)(a) In the absence of a membrane potential.(b) When the transport is opposed by a membrane potential of 70 mV.(c) In cach case, will hydrolysis of 1 mole of ATP suffice to drive the trans-port of 1 mole of ion, assuming pH 7.4 and the following cytoplamicconcentrations: ATP= 4.60 mM, P = 5.10 mM, ADP = 310 µM?

The standard free energy change (∆G°) of a chemical reaction is the amount of energy released in the…

Answered: In the situations described below, what…

Biochemistry

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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In the following situations, what is the free energy change if 1 mole of Na+is transported across a membrane from a region where the concentration is1 μM to a region where it is 100 mM?(Assume T = 37 °C.) (a) In the absence of a membrane potential. (b) When the transport is opposed by a membrane potential of 70 mV. (c) In each case, will hydrolysis of 1 mole of ATP suffice to drive the transport of 1 mole of ion, assuming pH 7.4 and the following cytoplasmic concentrations: ATP = 4.60 mM, Pi = 5.10 mM, ADP = 310 μM?
In the situations described below, what is the free energy change if 1 mole of Na+ is transported across a membrane from a region where the concentration is 48 μM to a region where it is 110 mM? (Assume T=37∘C.) When the transport is opposed by a membrane potential of 70 mV.
In the situations described below, what is the free energy change if 1 mole of Na+ is transported across a membrane from a region where the concentration is 48 μM to a region where it is 110 mM? (Assume T=37∘C.) In the absence of a membrane potential.
You are considering transport of Fe3+ out of a biological cell with a membrane potential of -60 mV. What is the value for delta psi in this case? (Make sure you express this value in proper units, i.e., as you would enter this value into the change in free energy of transport equation.)
Suppose that the concentration of CI outside the cell is 100 and inside the cell is 10 mmol/liter. The Nernst equation at 20°C is: Eton = 58 millivolts/z- [10810 (m)] [lonlin You set the membrane voltage at 0 millivolts using a voltage clamp, and measure membrane current. If Cl is the only ion crossing the membrane, you would expect to see: Onegative charges flowing into the cell negative charges flow out of the cell 0 current the membrane hyperpolarizes (becomes more negative)
Uniporters and ion channels support facilitated transport across cellular membranes. Although both are examples of facilitated transport, the rates of ion movement via an ion channel are roughly 104 - to 105 -fold faster than the rates of molecule movement via a uniporter. What key mechanisticdifference results in this large difference in transport rate?What contribution to free energy (ΔG) determines the direction of transport?
Uniporters and ion channels support facilitated transport across cellular membranes. Although both are examples of facilitated transport, the rates of ion movement via an ion channel are roughly 104- to 105-fold faster than the rates of molecule movement via a uniporter. What key mechanistic difference results in this large difference in transport rate? What contribution to free energy (ΔG) determines the direction of transport?
The sarcoplasmic reticulum Ca2+-ATPase, pumps 2 mol Ca2+ out of sarcomeres per mol ATP hydrolyzed. Given the following steady-state concentrations and a membrane potential of 67 mV (inside negative), calculate ΔG for the following active transport process at 37 ∘C and pH=7.4:2Ca2+(in)+ATP+H2O→2Ca2+(out)+ADP+Pi+H+
Distinguish between simple diffusion (SD), facilitated diffusion (FD), and active transport (AT) across a membrane for the following questions. (a) Which processes are energy dependent? (b) Which processes need some kind of carrier protein(s)? (c) Which processes can be saturated by substrate? (d) Which processes can establish a concentration gradient? (e) How much energy does it take to transport an uncharged substrate in, if its starting inside concentration is 10-fold greater than outside?
Name the three classes of membrane transport proteins. Explain which one or ones of these classes is able to move glucose and which can move bicarbonate (HCO3 −) against an electrochemical gradient. In the case of bicarbonate, but not glucose, the ΔG of the transport process has two terms.What are these two terms, and why does the second not apply to glucose? Why are cotransporters often referred to as examples of secondary active transport?
Calculate the energy cost (free-energy change) of pumping Ca2+ from thecytosol, where its concentration is about 1.0 × 10−7 M, to the extracellularfluid, where its concentration is about 1.0 mM. Assume a temperature of 37°C (body temperature in a mammal) and a standard transmembrane potentialof 50 mV (inside negative) for the plasma membrane.
Ouabain is a specific inhibitor of the active transport of sodium ions out of the cell and is therefore a valuable tool in studies of membrane transport mechanisms. Which of the following processes in your own body would you expect to be sensitive to inhibition by ouabain? Explain your answer in each case. a) Facilitated diffusion of glucose into a muscle cell b) Active transport of dietary phenylalanine across the intestinal mucosa c) Uptake of potassium ions by red blood cells d) Active uptake of lactose by the bacteria in your intestine

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