Assimilates lateral transport

In what follows, we discuss uptake, i.e., assimilation of metal ions from the environment into the organism itself. Later, in Chapter 8, we consider metal transport, storage, and homeostasis within organisms and cells. 

Ethanol strongly limits amino acid transport. It modifies the composition and the properties of the phospholipids of the plasmic membrane. The membrane becomes more permeable. The H+ ions of the medium massively penetrate the interior of the cell by simple diffusion. The membrane ATPase must increase its operation to control the intracellular pH. As soon as this task monopolizes the ATPase, the symport of the amino acids no longer functions. In other words, at the beginning of fermentation, and for as long as the ethanol concentration in the must is low, yeasts can rapidly assimilate amino acids and concentrate them in the vacuoles for later use, according to then-biosynthesis needs. 

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