To help understand this, remember that glucose is a polar molecule that cannot passively diffuse across cell membranes, which means that it acts as a solute.
However, if you have a solid foundation in a language, if you've been absorbing a language passively for many years, yes, you can make the jump to fluency relatively easily.
Perhaps they got fluent quickly in a language that they had already been studying or passively absorbing, or a language that's actually very similar to their native language.
From the lungs, freshly oxygenated blood flows back into the left atrium and passively passes through the mitral or bicuspid valve to fill the left ventricle.