Multiple diseases arise from sterol homeostasis disruption and are characterized at the molecular level by depletion or accumulation of sterol species. One such disease is Smith-Lemli-Opitz syndrome (SLOS) that results from genetic mutations in a particular cholesterol synthesis enzyme, which leads to depletion of cholesterol and accumulation of 7-dehydrocholesterol (7DHC). Recent in vivo work demonstrated that depleting/enriching specific sterol species modulated clathrin-mediated endocytosis (CME) that might contribute to the cellular phenotypes observed in disease states. The CME results were explained by softening mechanisms involving sterol lateral redistribution, but it remains a question as to why this occurs. Here, we take the outlook that differences in Gaussian curvature modulus and local lipid composition destabilize narrow necks in fission, reducing the membrane's apparent rigidity. Using membrane fluctuation analysis, we quantify sterol physical properties that partially define the fusion/fission energetic pathway, for example: the compressibility modulus, bending modulus, leaflet neutral surface, leaflet spontaneous curvature, bilayer thickness preference, and thickness contribution to the Gaussian modulus. Using these quantities, we make predictions on where sterol species will redistribute on strongly curved membranes. Finally, we use all-atom simulations of strongly curved fusion pore and hemifusion diaphragm geometries to quantify the sterol redistribution and compare to hypotheses. Comparing cholesterol and 7DHC physical properties, for example, the key statistically significant quantity is the thickness contribution to the Gaussian modulus, and we predicted that 7DHC would be less excluded from the fusion pore than cholesterol. All-atom molecular dynamics simulations of the fusion pore confirmed this hypothesis. The result correlates to in vivo experiments that showed reduced CME with 7DHC compared to cholesterol (p < 0.10). Other tests are ongoing.