Suppose that a plant cell membrane is permeable with Na*, CI ions and H20, but not with proteins. In addition, it is assumed that 0.05 M NaCl aqueous solution is present outside the cell membrane, and 0.001 M of protein (P) is present inside. The protein is ionized to p2*, z = %3D 20, and the opposite ion is CI". From this, calculate the theft potential that occurs between the cell membrane and the external solution in equilibrium. Assume that the activity coefficient of all ions is 1.0.

The diffusion rate of four different membrane proteins (A, B, C, and D) was measured using a FRAP experiment with purified liposomes. The FRAP recovery curves are shown below. (a) Which membrane protein exhibits the higher rate of diffusion in the lipid bilayer? A or B? C or D? (b) Explain the most likely cause of the difference in the recovery curves for proteins A and C.

The uptake of l-ascorbate (vitamin C) and its oxidized form, dehydro-l-ascorbic acid (DHAA), was evaluated in brush border membrane vesicles isolated from adult human small intestine. Ascorbate uptake was Na+-dependent and potential-sensitive (Km, 200 umol/L), whereas DHAA transport occurred through Na+-independent facilitated diffusion (Km, 800 µmol/L). If the Vmax of vitamin C import through channels is 401µmol/min/cm2, what import rate would you expect if the lumen contained 133 µmol/L of the version of vitamin C that moves through them?

Your research advisor would like you to measure the movement of a protein X using FRAP. The results of your FRAP experiment are shown below. What can you conclude? Fluorescence Intensity (Arbitrary Units) Time (Seconds) Time point of exposure to an intense laser Protein X appears to be completely immobilized in the membrane Protein X appears to be partially immobilized in the membrane You cannot make predictions about the mobility of Protein X with these data Protein X appears to be completely mobile in the membrane

Our current experimental procedure works because Con A adheres strongly to the nitrocellulose membrane while HRP hardly binds to the membrane at all. If HRP binds as strongly to the membrane as Con A does, our current scheme will not work. Assuming that's the case (HRP strongly binds to the membrane non-specifically, regardless of the presence of ConA), you will need to treat the membrane with an additional solution before treating it with HRP. What solution would that be? O Saturated NaCI solution. O Concentrated HCI. A membrane-binding protein. Concentrated glucose slution.

A one-to-one protein (P)-ligand (L) complexation (P + L PL) has a dissociation equilibrium constant (Kd) value of 100 nM at 25°C, and the Kd remains the same at 37°C. 1) What is AS of binding at 25°C? Assume ACp of the binding is 0 over the temperature range. AS = 1.34E2 kJ/(mol*K) (note the unit!!) (sig. fig =3) 2) What is the concentration of the PL complex formed at equilibrium when you mix 0.20 uM (microM) of Protein and 1.0 uM of Ligand together at 37°C? PL at equilibrium = 8.1E-1 uM (note the unit!!) (sig. fig =2)

In the absence of tension, MscL channel has an energy gap separating the closed and open states Eo = 50 kT. MscL opening is associated with a 20 nm2 in-plane protein expansion (change in A). Plot its open probability (Po) as a function of membrane tension. What will be the open probabilities of two MscL channels if one situates at the pole of the bacterial cell above, another in the middle?

b) If you soak an animal cell that is permeable to both water and glucose in either 5.5% glucose or 0.9% NaCl (both isosmotic solutions), the cell exposed to 5.5% glucose will gain water, while the cell exposed to 0.9% NaCl will not gain water. Predict why this is the case.

The following table shows experimental results of the glucose transport rate, mM/sec, following facilitated diffusion by glucose carrier proteins. (Recall: the starting conc. L represents glucose added to one side of the membrane; distilled water, omM of glucose was added to the other side of the membrane). The rate of glucose transport was 0.0031 mm/sec with 8mM of glucose (run number 4, highlighted); the rate decreased to 0.0017 mM/sec with 10mM of glucose (run 5, highlighted). Why was the rate of glucose transport slower when the concentration gradient was increased? Experiment Results Run Number Solute 1 1 2 2 3 33 4 4 5 6 6 Na Ch Glucose Na Ch Glucose Na Ch Glucose Nat Ch Glucose Na Ch Glucose Nat Cl Glucose Start Conc. L Start Conc. R (MM) (mM) 0.00 0.00 2.00 0.00 0.00 0.00 8.00 0.00 0.00 0.00 2.00 0.00 0.00 0.00 8.00 0.00 0.00 0.00 10.00 0.00 2.00 0.00 2.00 0.00 Carriers 500 500 500 500 700 700 700 700 100 100 700 700 Rate (mm/sec) 0.0000 0.0008 0.0000 0.0023 0.0000 0.0010…

You have a semi permeable membrane with a membrane potential of -90mV. You also have two ions that are both permeable to the membrane, Na and Cl. Na has a concentration of 10mM inside the membrane and 120mM outside the membrane. Cl has a concentration of 1.5mM inside the membrane and 77.5mM outside the membrane. Use the nernst equation to calculate the electrochemical equilibrium of both ions, and show in which direction the netflux would be for each ion.