Reason About Scientific Principles, Theories, and Models Practice Test

A lab studies diffusion of a small nonpolar anesthetic across a lipid bilayer. The membrane is modeled as a slab of thickness $L$ with steady-state flux $J = -D,\Delta C/L$. Two membranes have identical composition and temperature, but Membrane X is twice as thick as Membrane Y. If the same concentration difference $\Delta C$ is imposed across each, which prediction is most consistent with Fick’s law for the steady-state flux?

A DNA-binding protein recognizes a specific base sequence primarily through hydrogen bonding in the major groove. The experiment is repeated in heavy water (D$_2$O) instead of H$_2$O at the same temperature. Considering hydrogen-bond strength and isotope effects qualitatively, which prediction is most consistent with replacing H$_2$O by D$_2$O?