Which of the following molecules can diffuse through the membrane faster? CO2, CH4 Sugar, glucose H2O, H3O Ca2+, Ka1+ Solution H20 Water. oxygen is a small molecule and its non -polar makes the water molecules ,can pass through the membrane easyly by water diffusion calle osmosis.C02 ,the by product of cell respiration,is small enough to readily diffuse out of a cell. small uncharged lipid molecules can pass easyly the membrane. Large and charged molecules show slow movement. Glucose also move easyly across the membrane..