What definition of a solvent is given and which solvent is called 'universal' in organisms?
A solvent dissolves solutes to form a solution; water is the universal solvent in organisms.
Why is water important in the human body percentage-wise and functionally?
Water makes up 60–70% of the body and dissolves/transports nutrients, gases, salts, and wastes; enables enzyme activity.
How does water assist digestion after large molecules are broken down?
It dissolves small products like glucose, enabling absorption across the gut wall into the bloodstream.
Why do many enzymes require water to function?
Enzymes often act in aqueous solutions; substrates must be dissolved for enzyme-substrate interactions.
What wastes dissolve in water for excretion and where are they formed into urine?
Urea and salts dissolve in water; kidneys filter wastes into water to form urine.
How does water prevent toxic buildup in the body?
By dissolving waste molecules and carrying them out of the body in urine.
What role does water play in blood and transport in animals?
Blood plasma is mostly water, carrying dissolved gases, nutrients, and hormones throughout the body.
How does water aid mineral transport in plants?
Water in xylem dissolves soil mineral ions like nitrates and magnesium and transports them to leaves.
List key substances transported by water in humans and plants.
Humans: Oâ‚‚, COâ‚‚, glucose, hormones. Plants: nitrates, magnesium ions dissolved in xylem.
Summarize why water as a solvent is essential for digestion, excretion, and transport.
It dissolves nutrients for absorption, wastes for safe excretion, and substances for distribution in blood or xylem.
Define osmosis succinctly including direction of water movement.
Osmosis is diffusion of water from higher water concentration (dilute) to lower water concentration (concentrated) across a partially permeable membrane.
What is a partially permeable membrane in biological terms?
A membrane allowing small molecules like water to pass while blocking larger solutes such as sugars or proteins.
What happens to animal cells if too much water enters or leaves?
If too much enters: cell may burst (lysis). If too much leaves: cell shrinks (crenation).
Describe the effect of water entering a plant cell.
Vacuole swells, cell becomes turgid—firm and supported.
What occurs when a plant cell loses water?
Vacuole shrinks; cell becomes flaccid or may become plasmolysed.
Give a concise definition of osmosis direction as summarized.
Movement of water by diffusion from high water concentration to low water concentration.
What is osmosis?
Diffusion of water through a partially permeable membrane from higher to lower water concentration.
Does osmosis require cellular energy (ATP)?
No; it is a passive process using kinetic energy of water molecules.
What must a membrane be for osmosis to occur?
Partially permeable, allowing water but blocking larger solutes.
How does osmosis differ from regular diffusion?
Osmosis moves only water and needs a partially permeable membrane; diffusion can move many solutes and may not need a membrane.
Why is osmosis important for cells?
It maintains water balance and keeps cells hydrated and properly shaped.
Why does osmosis not require ATP?
It relies on the kinetic energy of water molecules and concentration gradients.
How does a plant cell respond when water enters by osmosis?
It becomes turgid and supported by the cell wall.
What happens to an animal cell that gains too much water?
It may swell and burst (lyse).
What occurs when water leaves a plant cell?
It becomes flaccid and may undergo plasmolysis.
Why is dialysis tubing used in osmosis experiments?
It mimics a partially permeable cell membrane, letting water pass but blocking large solutes like sucrose.
What materials are needed for a dialysis tubing osmosis experiment?
Dialysis tubing, sucrose solutions, distilled water, beakers, strings, measuring cylinders, balance, timer.
Outline the basic steps of the dialysis tubing experiment.
Fill tubing with sucrose, record mass, immerse in distilled water, wait, reweigh to measure mass change.
What result is expected when tubing with concentrated sucrose is placed in distilled water?
Water enters tubing, so mass increases.
What indicates no net movement in the dialysis tubing experiment?
Inside and outside solutions having the same concentration, so mass remains unchanged.
What is an independent variable in the dialysis tubing investigation?
Sucrose concentration.
What is a dependent variable for that investigation?
Change in mass or volume of the tubing.
Name key controlled variables to keep constant.
Time, temperature, solution volumes, and tubing size.
How can the experiment's accuracy be improved?
Use a digital balance, repeat trials, test multiple concentrations, and control temperature/time.
What is investigated when plant tissues are placed in pure water versus concentrated solutions?
How plant cells gain or lose water by osmosis, affecting firmness and plasmolysis.
What is the main purpose of placing plant tissue in solutions of different sucrose or salt concentrations?
To observe osmosis by measuring water movement into or out of tissue via change in mass or length.
List three materials needed for the osmosis experiment.
Sucrose/salt solutions, beakers or test tubes, ruler or balance.
What happens to plant tissue in distilled water (0%)?
Water enters cells; tissue becomes turgid and may swell.
Describe plasmolysis in one sentence.
Plasmolysis is when the cell membrane pulls away from the cell wall due to excessive water loss.
How should results be recorded after the experiment?
Record initial and final mass/length, then calculate percentage change.
What is plotted on the Y and X axes for the % mass change graph?
Y-axis: % change in mass; X-axis: sucrose concentration.
What does the graph crossing zero indicate?
The isotonic point where no net water movement occurs.
Define 'hypertonic' and its effect on cells.
Hypertonic: outside is more concentrated; water leaves the cell causing shrinkage.
Give examples of independent and dependent variables in the experiment.
Independent: sucrose/salt concentration. Dependent: change in mass or length.
Name three controlled variables to keep constant.
Time, temperature, size of tissue.
Why do plants stay upright according to the text?
Because turgor pressure from water-filled vacuoles pushes the membrane against the rigid cell wall.
What happens to turgor pressure when cells lose water?
Turgor pressure drops, cells become flaccid, causing wilting.
Summarize how turgor pressure develops.
Water enters vacuole by osmosis, vacuole expands and presses membrane against cell wall creating outward pressure.
What is osmosis in terms of water potential?
Net movement of water from higher to lower water potential through a partially permeable membrane.
How does adding solute affect water potential?
Adding solute lowers water potential, reducing free water movement.
Why is a partially permeable membrane important for osmosis?
It allows water molecules through while blocking larger solutes, enabling selective water movement.
Describe water movement between soil and root hair cells.
Water moves from dilute soil (higher water potential) into root cell sap (lower water potential).
What happens to a plant cell placed in a dilute (hypotonic) solution?
Water enters by osmosis; vacuole fills, cell becomes turgid and firm due to turgor pressure.
Define 'turgor pressure' in plant cells.
Pressure from water pushing the cell membrane against the rigid cell wall.
What does a partially permeable membrane allow and block?
Allows water to pass but blocks many solutes.
How does water move relative to water potential?
Water moves from high water potential (dilute) to low water potential (concentrated).
What occurs when a plant cell is placed in a concentrated (hypertonic) solution?
Water leaves by osmosis, vacuole shrinks, cell becomes flaccid; plasmolysis may occur.
Define 'plasmolysis' and its reversibility.
Membrane detaches from cell wall due to extreme water loss; usually irreversible.
Contrast turgid and flaccid plant cells.
Turgid: full of water and firm. Flaccid: has lost water and is soft or weak.
Why is osmosis important for plant water uptake?
It moves water from soil (high potential) into roots (low potential) via root hair cells.
How does turgor pressure help plants structurally?
Water-filled vacuoles make cells turgid, supporting leaves and stems.
What happens to plants without proper osmosis?
They lose turgor, wilt, and struggle to transport minerals.
How does osmosis affect animal cell hydration?
Water moves in or out to balance body fluids, preventing dehydration or overhydration.
Why must osmosis be tightly regulated in animal cells?
Animal cells lack cell walls, so unregulated water movement can cause bursting or shrinking.
How do kidneys use osmosis?
Osmosis controls water reabsorption to maintain body water balance.
Summarize the role of water potential and osmosis in living organisms.
They drive water flow into/out of cells, supporting plant turgidity and animal fluid balance.
What does the graph crossing zero indicate?
The isotonic point where no net water movement occurs.
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