AP Biology Flashcards: Tonicity And Osmoregulation

What this deck covers

This deck focuses on Tonicity And Osmoregulation, giving you a quick way to review the definitions, rules, and examples that matter most for AP Biology.

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Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: Which cellular structure allows plant cells to resist lysis in hypotonic solutions?

Answer: The rigid cell wall. Rigid walls withstand internal pressure from water uptake.

Flashcard 2: Explain the effect of diuretics on water balance.

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

Flashcard 3: What is a nonpenetrating solute?

Answer: A solute that cannot cross the membrane and therefore affects tonicity. These solutes create permanent osmotic gradients across membranes.

Flashcard 4: What happens to a cell in an isotonic solution?

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

Flashcard 5: What is tonicity in the context of osmosis across a selectively permeable membrane?

Answer: A solution's ability to cause net water movement and cell volume change. Tonicity specifically measures osmotic effect, not just total solute concentration.

Flashcard 6: State the relationship between tonicity and osmolarity.

Answer: Tonicity depends on the osmolarity and the cell's permeability to solutes. Only nonpenetrating solutes contribute to tonicity effects.

Flashcard 7: Name a condition where blood plasma is hypotonic.

Answer: Hyponatremia is a condition where blood plasma is hypotonic. Low sodium levels create hypotonic blood conditions.

Flashcard 8: Identify the direction of water movement in osmosis.

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

Flashcard 9: What happens to a plant cell placed in a hypertonic solution?

Answer: It plasmolyzes as water leaves and the membrane pulls from the wall. Extreme water loss causes membrane separation from rigid wall.

Flashcard 10: Which structure in plants helps minimize water loss?

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

Flashcard 11: State the relationship between tonicity and osmolarity.

Answer: Tonicity depends on the osmolarity and the cell's permeability to solutes. Only nonpenetrating solutes contribute to tonicity effects.

Flashcard 12: What is the key difference between tonicity and osmolarity?

Answer: Tonicity depends on nonpenetrating solutes; osmolarity counts all solutes. Only membrane-impermeable solutes create sustained osmotic pressure.

Flashcard 13: What happens to a plant cell placed in a hypotonic solution?

Answer: It becomes turgid due to water uptake and turgor pressure. Cell wall prevents lysis while allowing optimal turgor pressure.

Flashcard 14: What type of solution is required for a plant cell to become turgid?

Answer: A hypotonic solution causes a plant cell to become turgid. Water influx creates turgor pressure against the cell wall.

Flashcard 15: What is an osmoregulator?

Answer: An organism that maintains internal osmolarity different from its environment. Actively maintains optimal internal conditions regardless of environment.

Flashcard 16: What role does urea play in osmoregulation?

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

Flashcard 17: Which part of the nephron is responsible for reabsorbing water?

Answer: The proximal convoluted tubule and loop of Henle reabsorb water. Both regions actively reclaim water from the filtrate.

Flashcard 18: State the consequence of a cell bursting due to excess water intake.

Answer: Lysis occurs when a cell bursts due to excess water intake. Cell membrane ruptures from excessive water influx.

Flashcard 19: Describe the effect of a hypotonic solution on a cell.

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

Flashcard 20: Define osmoregulation.

Answer: Osmoregulation is the control of water and solute concentrations in a cell or organism. Maintains proper cell volume and prevents osmotic stress.

Flashcard 21: What is the function of the glomerulus in the nephron?

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

Flashcard 22: Identify the hormone that regulates water reabsorption in kidneys.

Answer: Antidiuretic hormone (ADH) regulates water reabsorption. Increases water permeability of collecting duct cells.

Flashcard 23: What happens to an animal cell placed in a hypertonic solution?

Answer: It shrivels (crenates) as water exits. Water loss causes membrane to fold inward at cell edges.

Flashcard 24: Identify the hormone that regulates water reabsorption in kidneys.

Answer: Antidiuretic hormone (ADH) regulates water reabsorption. Increases water permeability of collecting duct cells.

Flashcard 25: Which part of the nephron is responsible for reabsorbing water?

Answer: The proximal convoluted tubule and loop of Henle reabsorb water. Both regions actively reclaim water from the filtrate.

Flashcard 26: What is a penetrating solute (in tonicity problems)?

Answer: A solute that can cross the membrane and may not sustain tonicity effects. These solutes equilibrate across membranes, eliminating osmotic effect.

Flashcard 27: What is an osmoconformer?

Answer: An organism whose internal osmolarity matches its external environment. No energy spent maintaining osmotic gradients against environment.

Flashcard 28: What is a solute in a solution, in the context of tonicity?

Answer: A dissolved substance that contributes to total solute concentration. Only nonpenetrating solutes affect tonicity in osmotic calculations.

Flashcard 29: Which cellular structure allows plant cells to resist lysis in hypotonic solutions?

Answer: The rigid cell wall. Rigid walls withstand internal pressure from water uptake.

Flashcard 30: What is a selectively permeable membrane?

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

Flashcard 31: Which direction does water move by osmosis relative to solute concentration?

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

Flashcard 32: What does isotonic mean for a cell in a surrounding solution?

Answer: No net water movement; cell volume remains stable. Equal effective solute concentrations create osmotic equilibrium.

Flashcard 33: What is the primary osmoregulatory challenge for freshwater animals?

Answer: Gaining water and losing salts by osmosis and diffusion. Hypotonic environment causes continuous water influx and salt loss.

Flashcard 34: Which hormone increases water reabsorption in the kidney collecting ducts?

Answer: Antidiuretic hormone (ADH, vasopressin). ADH makes collecting ducts more permeable to water reabsorption.

Flashcard 35: What is plasmolysis?

Answer: Plasmolysis is the process where plant cells lose water and the cell membrane detaches from the cell wall. Occurs when plant cells are placed in hypertonic solutions.

Flashcard 36: Which option best describes negative feedback in osmoregulation?

Answer: A deviation triggers responses that restore internal osmolarity toward a set point. Homeostatic mechanism maintains stable internal water balance.

Flashcard 37: Which structure in plants helps minimize water loss?

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

Flashcard 38: Describe the role of contractile vacuoles in osmoregulation.

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

Flashcard 39: What does hypertonic mean for a cell in a surrounding solution?

Answer: Solution has higher effective solute; water leaves the cell. Water moves out to equalize solute concentrations across membrane.

Flashcard 40: What is turgor pressure?

Answer: Pressure of the cell contents against the plant cell wall after water uptake. Created when water enters cell but wall prevents expansion.

Flashcard 41: Identify the tonicity: Outside and cytosol have equal nonpenetrating solute.

Answer: Isotonic. Equal concentrations prevent net water movement across membrane.

Flashcard 42: What does hypertonic mean for a cell in a surrounding solution?

Answer: Solution has higher effective solute; water leaves the cell. Water moves out to equalize solute concentrations across membrane.

Flashcard 43: What does hypotonic mean for a cell in a surrounding solution?

Answer: Solution has lower effective solute; water enters the cell. Water moves in to dilute higher internal solute concentration.

Flashcard 44: What is lysis in the context of osmosis?

Answer: Cell rupture caused by excessive water influx. Occurs when osmotic pressure exceeds membrane strength.

Flashcard 45: Which type of organism primarily uses contractile vacuoles?

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

Flashcard 46: Which organ is primarily responsible for osmoregulation in mammals?

Answer: The kidneys are primarily responsible for osmoregulation in mammals. Filter blood and regulate water and electrolyte balance.

Flashcard 47: What is osmosis?

Answer: Diffusion of water across a selectively permeable membrane. Water moves down its concentration gradient through membrane pores.

Flashcard 48: What is lysis in the context of osmosis?

Answer: Cell rupture caused by excessive water influx. Occurs when osmotic pressure exceeds membrane strength.

Flashcard 49: What type of solution is required for a plant cell to become turgid?

Answer: A hypotonic solution causes a plant cell to become turgid. Water influx creates turgor pressure against the cell wall.

Flashcard 50: How does the body respond to dehydration in terms of ADH?

Answer: The body increases ADH secretion to promote water reabsorption. Conserves body water by increasing kidney reabsorption.

Flashcard 51: Identify the primary challenge for terrestrial animals in osmoregulation.

Answer: Terrestrial animals must conserve water while excreting wastes. Must balance water retention with waste elimination.

Flashcard 52: What is an osmoregulator?

Answer: An organism that maintains internal osmolarity different from its environment. Actively maintains optimal internal conditions regardless of environment.

Flashcard 53: Which hormone decreases blood osmolarity by increasing water reabsorption?

Answer: Antidiuretic hormone (ADH) decreases blood osmolarity. Promotes water retention to dilute blood solutes.

Flashcard 54: What happens to a cell in an isotonic solution?

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

Flashcard 55: Which type of organism primarily uses contractile vacuoles?

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

Flashcard 56: What is the role of the rectal gland in sharks?

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

Flashcard 57: What is the role of the loop of Henle in water reabsorption?

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

Flashcard 58: What is the primary osmoregulatory challenge for marine bony fish?

Answer: Losing water and gaining salts due to a hypertonic environment. Hypertonic seawater continuously draws water from fish tissues.

Flashcard 59: What is the primary osmotic challenge for freshwater fish?

Answer: Freshwater fish must excrete excess water and retain salts. Hypotonic environment requires active water removal.

Flashcard 60: Identify the tonicity: Outside has higher nonpenetrating solute than cytosol.

Answer: Hypertonic. Higher nonpenetrating solute creates net water efflux from cell.

Flashcard 61: What is a solute in a solution, in the context of tonicity?

Answer: A dissolved substance that contributes to total solute concentration. Only nonpenetrating solutes affect tonicity in osmotic calculations.

Flashcard 62: Which part of the brain regulates thirst?

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

Flashcard 63: What is a nonpenetrating solute?

Answer: A solute that cannot cross the membrane and therefore affects tonicity. These solutes create permanent osmotic gradients across membranes.

Flashcard 64: Identify the effect of increased ADH on urine concentration.

Answer: Urine becomes more concentrated (greater water reabsorption). More ADH increases water reabsorption, reducing urine volume.

Flashcard 65: What is plasmolysis?

Answer: Plasmolysis is the process where plant cells lose water and the cell membrane detaches from the cell wall. Occurs when plant cells are placed in hypertonic solutions.

Flashcard 66: Which group is most commonly osmoconformers: marine invertebrates or freshwater fish?

Answer: Marine invertebrates. Their body fluids match seawater osmolarity naturally.

Flashcard 67: Name a condition where blood plasma is hypotonic.

Answer: Hyponatremia is a condition where blood plasma is hypotonic. Low sodium levels create hypotonic blood conditions.

Flashcard 68: What is the function of the glomerulus in the nephron?

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

Flashcard 69: What is crenation?

Answer: Shriveling of an animal cell due to water loss in a hypertonic solution. Cell membrane shrinks and creates characteristic spiky appearance.

Flashcard 70: What is the term for the movement of water across a semipermeable membrane?

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

Flashcard 71: Which option best describes negative feedback in osmoregulation?

Answer: A deviation triggers responses that restore internal osmolarity toward a set point. Homeostatic mechanism maintains stable internal water balance.

Flashcard 72: What does isotonic mean for a cell in a surrounding solution?

Answer: No net water movement; cell volume remains stable. Equal effective solute concentrations create osmotic equilibrium.

Flashcard 73: Identify the process by which salt is actively transported out of saltwater fish.

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

Flashcard 74: Explain the effect of diuretics on water balance.

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

Flashcard 75: What is osmosis?

Answer: Diffusion of water across a selectively permeable membrane. Water moves down its concentration gradient through membrane pores.

Flashcard 76: What is the term for the movement of water across a semipermeable membrane?

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

Flashcard 77: What happens to a plant cell placed in an isotonic solution?

Answer: It becomes flaccid due to reduced turgor pressure. Reduced turgor makes plant tissue soft and wilted.

Flashcard 78: State the consequence of a cell bursting due to excess water intake.

Answer: Lysis occurs when a cell bursts due to excess water intake. Cell membrane ruptures from excessive water influx.

Flashcard 79: What is tonicity?

Answer: 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.

Flashcard 80: What is a selectively permeable membrane?

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

Flashcard 81: Which hormone increases water reabsorption in the kidney collecting ducts?

Answer: Antidiuretic hormone (ADH, vasopressin). ADH makes collecting ducts more permeable to water reabsorption.

Flashcard 82: Which cells are responsible for maintaining osmotic balance in the brain?

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

Flashcard 83: What is tonicity?

Answer: 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.

Flashcard 84: What is the main nitrogenous waste in most mammals, relevant to water conservation?

Answer: Urea. Less toxic than ammonia but requires some water for excretion.

Flashcard 85: What happens to an animal cell placed in a hypertonic solution?

Answer: It shrivels (crenates) as water exits. Water loss causes membrane to fold inward at cell edges.

Flashcard 86: What does a hypertonic solution cause a cell to do?

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

Flashcard 87: What is the function of the nephron in osmoregulation?

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

Flashcard 88: Which structure prevents animal cells from becoming turgid in hypotonic solutions?

Answer: No rigid cell wall is present in animal cells. Animal cell membranes lack rigid walls to resist osmotic pressure.

Flashcard 89: What happens to an animal cell placed in an isotonic solution?

Answer: It maintains normal volume with no net water movement. Equal solute concentrations prevent osmotic water movement.

Flashcard 90: What is osmolarity?

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

Flashcard 91: What is a stomatal function in osmoregulation?

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

Flashcard 92: What does hypotonic mean for a cell in a surrounding solution?

Answer: Solution has lower effective solute; water enters the cell. Water moves in to dilute higher internal solute concentration.

Flashcard 93: What is the advantage of producing uric acid instead of urea for some animals?

Answer: It conserves water because uric acid can be excreted as a paste. Minimal water loss makes this ideal for arid environments.

Flashcard 94: What happens to an animal cell placed in a hypotonic solution?

Answer: It swells and may lyse. Water influx causes swelling; no cell wall provides structural resistance.

Flashcard 95: What is crenation?

Answer: Shriveling of an animal cell due to water loss in a hypertonic solution. Cell membrane shrinks and creates characteristic spiky appearance.

Flashcard 96: What is anhydrobiosis?

Answer: Anhydrobiosis is a dormant state that allows survival in dry conditions. Extreme dehydration tolerance by suspending metabolism.

Flashcard 97: What is tonicity in the context of osmosis across a selectively permeable membrane?

Answer: A solution's ability to cause net water movement and cell volume change. Tonicity specifically measures osmotic effect, not just total solute concentration.

Flashcard 98: Identify the primary challenge for terrestrial animals in osmoregulation.

Answer: Terrestrial animals must conserve water while excreting wastes. Must balance water retention with waste elimination.

Flashcard 99: What is the role of aquaporins in osmosis?

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

Flashcard 100: What is turgor pressure?

Answer: Pressure of the cell contents against the plant cell wall after water uptake. Created when water enters cell but wall prevents expansion.