BIOFOUND 5.2 Osmoregulation pt 1`

Osmoregulation

The process by which organisms control the concentration of water and electrolytes in their bodies to maintain homeostasis.

Electrolytes

Charged ions (e.g., Na⁺, K⁺, Cl⁻) that help regulate fluid balance, nerve function, and muscle contractions.

Osmotic Stress

A condition where there is an imbalance in water and solute concentrations between the inside and outside of a cell, potentially leading to damage or cell death.

Disturbance in Water/Electrolyte Balance

Can lead to osmotic stress, which may cause cells to shrink or swell excessively, resulting in malfunction or death.

Diffusion

The passive movement of molecules from an area of high concentration to low concentration.

Osmosis

The diffusion of water across a selectively permeable membrane from areas of low solute concentration to high solute concentration.

Osmolarity

The total concentration of solutes in a solution.

Hypertonic Solution

Higher solute concentration outside the cell; water moves out, causing the cell to shrink.

Hypotonic Solution

Lower solute concentration outside the cell; water moves in, causing the cell to swell.

Isotonic Solution

Equal solute concentrations inside and outside the cell; no net water movement.

Cell Response in Hypertonic Environment

Cells lose water and shrink.

Cell Response in Hypotonic Environment

Cells gain water and swell.

Osmoconformers

Animals that maintain internal conditions that are similar to their external environment (e.g., most marine invertebrates, sharks).

Osmoregulators

Animals that actively regulate internal osmolarity independent of the external environment (e.g., freshwater fish, mammals).

Marine Fish Osmoregulation

Face dehydration due to water loss by osmosis; they drink seawater and excrete salts through gills and urine.

Freshwater Fish Osmoregulation

Face water gain by osmosis; they excrete large volumes of dilute urine and actively uptake salts through gills.

Euryhaline Fish

Fish that can live in both marine and freshwater environments; they switch osmoregulatory strategies by altering gill function, ion transport, and hormone levels.

Terrestrial Animal Osmotic Stress

Lose water through evaporation, urine, and feces; must conserve water and regulate electrolytes to avoid dehydration.

Retention

The process of keeping water and/or solutes in the body.

Filtration

Movement of fluid and solutes out of blood and into a tubule or other excretory structure.

Reabsorption

Process of reclaiming needed water and solutes back into the body from the filtrate.

Malpighian Tubules (Insects)

Excretory organs that remove wastes and help with osmoregulation by secreting solutes and water into the tubules.

Hindgut (Insects)

Reabsorbs water and ions from the tubule contents to minimize water loss and maintain internal balance.