Question

Read each question carefully. Write your response in the space provided for each part of each question. Answers must be written out in paragraph form. Outlines, bulleted lists, or diagrams alone are not acceptable and will not be scored.

Scientists are testing substance L to determine how it enters mammalian cells in a culture. The cells maintain a  120 millimolar (mM) intracellular concentration of substance L . The scientists determined the rate of entry of substance L into the cells at various external concentrations of substance L (10 to 100 mM) in culture medium (Table: Attached)

Table 1. Rate of entry of substance L into mammalian cells in culture External concentration of substance L (MM) Rate of entry of substance L into cell as a percent of maximum 5% 10 20 25% 30 45% 65% 80% 60 90% 70 95% 100% 80 90 100% 100 100% The cells maintain substance L at an internal concentration of 120 mM.

(a) Identify the most likely mode of transport across the membrane for substance L. Explain how information provided helps determine the most likely mode of transport.

(b) On the axes provided, construct an appropriately labeled line graph with correct scale and units to illustrate the data in Table 1. (Use graph below)

(c) Determine the external concentration of substance L that will result in one-half of the maximal entry rate.

d) Predict the likely effect on the ability of substance L to enter the cells if substance L is attached to a large protein instead of free in the culture.

Answer 1