AAMC FL Practice Exam

For a transporter to be effective under low food conditions, it is crucial for the transporter to have a high affinity for the substrate. When food availability is limited, the concentration of substrates (like nutrients) in the environment is low. A high affinity allows the transporter to bind substrates more effectively even when their concentration is minimal, ensuring that the organism can still acquire the necessary nutrients despite scarcity.

This characteristic is especially important for survival in challenging environments where competition for limited resources can occur. It maximizes nutrient uptake efficiency, facilitating the organism's ability to thrive despite reduced substrate availability.

Options suggesting that the transporter's size must increase, the number of transporters should decrease, or that action should be faster do not address the core challenge of low substrate concentration. Instead, they might even hinder the transport process. Thus, the high affinity is the most critical aspect for effective transport in such conditions.