Yeasts reproduce primarily by:

A. Plasmolysis: Plasmolysis occurs when a bacterial cell is placed in a hypertonic solution, causing water to move out of the cell via osmosis. The loss of water leads to shrinkage of the cytoplasm away from the cell wall, which can inhibit growth or cause cell death if prolonged. This process is a direct result of osmotic pressure differences across the cell membrane.

B. Osmosis into the cell: Osmosis into the cell occurs when water moves from a region of lower solute concentration to higher solute concentration inside the cell, typically in a hypotonic solution. In a hypertonic environment, water moves out of the cell, not into it, making this explanation incorrect for cell shrinkage.

C. Diffusion of solutes: While solutes do diffuse across membranes, the shrinkage of a bacterium in a hypertonic solution is primarily due to water movement, not solute diffusion. Solute movement alone does not account for the immediate loss of cell turgor and cytoplasmic shrinkage seen in plasmolysis.

Bacterial cell membranes are composed of a phospholipid bilayer in which the hydrophilic (water-attracting) heads face outward toward the aqueous environment both inside and outside the cell, while the hydrophobic (water-repelling) tails are buried in the interior of the membrane, away from water. This arrangement creates a selectively permeable barrier that regulates the movement of substances into and out of the cell. The correct orientation of phospholipids is critical for maintaining membrane integrity, fluidity, and proper function of embedded proteins, transport systems, and signaling molecules.