Tonicity and Osmoregulation - AP Biology

Plant cell membrane detaches from cell wall due to water loss. Water loss shrinks cytoplasm away from inflexible cell wall.

Yes; they drink seawater and excrete excess salts. Drinking replaces lost water; gills pump out excess salt.

Salt is actively transported out by chloride cells in the gills. Specialized cells actively pump out excess sodium chloride.

A membrane that allows some substances to cross more easily than others. Permeability varies by substance size, charge, and lipid solubility.

From lower solute concentration to higher solute concentration. Water dilutes concentrated regions to achieve equilibrium.

Urea maintains osmotic balance by being reabsorbed in the kidneys. Acts as an osmolyte to concentrate urine effectively.

The glomerulus filters blood to form a filtrate in the nephron. Initial step in urine formation within Bowman's capsule.

Aldosterone increases sodium reabsorption and potassium excretion in the kidneys. Promotes sodium retention and potassium loss for volume regulation.

Astrocytes help maintain osmotic balance in the brain. Glial cells that regulate brain fluid osmolarity.

Nephrons filter blood, reabsorb water, and excrete waste to maintain osmotic balance. The functional unit of the kidney for water and solute regulation.

A hypotonic solution causes a cell to gain water and swell. Lower external solute concentration drives water into the cell.

Water moves from regions of low solute concentration to high solute concentration. Water follows its concentration gradient via osmosis.

Diuretics increase urine production, promoting water excretion. Inhibit sodium reabsorption, leading to water loss.

In an isotonic solution, a cell experiences no net water movement. Equal solute concentrations create osmotic equilibrium.

The hypothalamus regulates thirst. Contains osmoreceptors that detect blood osmolarity changes.

Aquaporins facilitate the rapid transport of water across cell membranes. These channel proteins increase membrane water permeability.

Protists, such as amoebas and paramecia, use contractile vacuoles. Single-celled organisms in freshwater environments need this adaptation.

The loop of Henle creates a concentration gradient to facilitate water reabsorption. Countercurrent flow concentrates urine and conserves water.

Osmosis is the movement of water across a semipermeable membrane. Passive diffusion driven by concentration gradients.

The cuticle helps minimize water loss in plants. Waxy layer reduces water loss through transpiration.

Salt is actively transported out by chloride cells in the gills. Specialized cells actively pump out excess sodium chloride.

Marine fish drink seawater and excrete salt through gills. Osmoregulation in hypertonic seawater environment.

The rectal gland excretes excess salts in sharks. Specialized organ for concentrated salt elimination.

Stomata regulate gas exchange and water loss in plants. Guard cells control water vapor loss and CO₂ uptake.

Aldosterone increases sodium reabsorption and potassium excretion in the kidneys. Promotes sodium retention and potassium loss for volume regulation.

Contractile vacuoles expel excess water from cells to maintain osmotic balance. Prevent cell bursting in hypotonic environments.

Osmolarity is the total concentration of solute particles in a solution. Measured in osmoles per liter of solution.

A hypertonic solution causes a cell to lose water and shrink. Higher solute concentration outside draws water out via osmosis.

Tonicity is the ability of a solution to cause a cell to gain or lose water. Based on relative solute concentrations between solution and cell.