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#hypertonic conditions

2 public questions tagged with this topic.

Membrane Transportation

What is the effect of hypertonic conditions on cells?

Tonicity governs cell volume by defining relative effective osmolarity of extracellular fluid compared with cytoplasm, usually near 300 milliosmoles. Hypertonic environment contains higher concentration of non-penetrating solutes like sodium chloride, mannitol or sucrose, leading to lower water potential described by psi equals psi solute plus psi pressure. Since water diffuses toward lower water potential via aquaporins and lipid bilayer, net efflux occurs from cell to surroundings. Loss of water concentrates intracellular proteins and solutes, decreases cell volume, increases ionic strength

Ref: Alberts et al., Molecular Biology of the Cell, Chapter 11: Hypertonic Effects on Cell Volume and Regulatory Mechanisms.

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Microbial Physiology

Which bacterial structure prevents plasmolysis in hypertonic conditions?

Hypertonic surroundings draw water out of bacterial cytoplasm through semipermeable inner membrane, generating inward osmotic pressure that tends to detach inner membrane from wall and shrink cytoplasm, a process termed plasmolysis. Survival depends on mechanical resistance supplied by peptidoglycan, a covalently crosslinked heteropolymer forming a single macromolecule sacculus surrounding entire cell, often described as exoskeleton. Its glycan strands crosslinked via peptide bonds possess high tensile strength, allowing it to withstand internal turgor of 2 to5 atmospheres in Gram-negatives an

Ref: Rojas et al., PNAS 2014, Stiffness of Bacterial Cell Wall; Alberts et al., Molecular Biology Cell, Cell Wall Mechanics.

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