nline.net/bbcswebdav/pid-2729738-dt-content-rid-20518143 1/courses/B2740-15 page
ID: 281076 • Letter: N
Question
nline.net/bbcswebdav/pid-2729738-dt-content-rid-20518143 1/courses/B2740-15 page 3 of:5 3. You discover a light-activated symport that transports Na* and pyruvate into the cell. You call this symport Symp You create an artificial vesicle where the only protein in the lipid is Sympl. Sympl is oriented such that the cytoplasmic portion is inside the vesicle and the extracellular portion is on the outside of the vesicle (and thus similar to the arrangement of Sympl on the plasma membrane of a cell). Your starting conditions are: Circle one: 210 or 212 Lab Section A. 50 mM of Na" inside and outside the vesicle. B. All the pyruvate is on the outside of the vesicle and there is no pyruvate inside the vesicle. C. Test tube in the dark. a) Given these starting conditions, is there a concentration gradient of pyruvate? (2 points) b) You take the vesicles at the starting conditions (as described above in A, B, and C above) add light and examine the vesicles after 5 minutes. Will the concentration of Na" outside the vesicle become higher than 50 mM, lower than 50 mM, or stay at 50 mM? Explain. (3 points) c) You create vesicles that have Symp/ (oriented as described above) and a Na" leak channel. You place the vesicles at starting conditions (as described in A, B, and C above), add light, and examine the vesicles after 5 minutes. In which direction do you predict pyruvate will be transported? (2 points) d) You examine the vesicles from 3e for Na" 5 minutes after exposure to light. Will the concentration of Na' outside the vesicle become higher than 50 mM, lower than 50 mM, or stay at 50 mM? Explain. (5 points) upExplanation / Answer
3.a. Yes, there is a concentration gradient for pyruvate because there are different concetrations outside and inside de vesicle, as the text says there is no pyruvate outside and pyruvate inside the cell.
b. The concentration outside the vesicle will be lower than 50mM because Symp 1 is a symport for Na+, so if there is no pyruvate outside, it will enter, and along with it also the Na+. That is why with time there would be less Na+ outside and more inside.
c. I predict the pyruvate will be transported inside the vesicle, as there is no pyruvate there. The different in concentrations will create a concentration gradient that will provoke the pyruvate to move inside.
d. The concentration of Na+ would be the same outside and inside the vesicle, although the Na+ will be transported inside with the pyruvate in the symport Symp 1, the leak channel will try to restore the concentration of Na+ so it would transpor it outside, keeping these way the concentration the same at both sides of the membrane.
e. I predict that it will not open because there is no change in the voltage, and this channels open up when the voltage changes. In the start conditions the concentration of Na+ are the same, so there would not be different concentration of electrical charges, and neither a change in voltage that could provoke a change in the channel.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.