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 1). 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

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.

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 1). Table 1. Rate of entry of substance 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 25% 20 45% 30 65% 40 80% 50 90% 60 95% 70 100% 80 100% 90 100% 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 Table 1. Rate of entry of substance L into mammalian cells in culture External Rate of entry of concentration substance L into cell of substance as a percent L (mM) maximum 10 5% 20 25% 30 45% 40 65% 50 80% 60 90% 70 95% 80 100% 90 100% 100 100% The cells maintain substance L at an internal concentration of 120 mM.