bio osmosis and diffusion lab

What is a solute?

A substance that is dissolved in a solvent

What is a solvent?

The substance that dissolves the solute

What is a solution?

A homogeneous mixture of solute and solvent.

Which molecule crossed the dialysis bag when phenolphthalein and NaOH were used?

NaOH moved into the bag, turning it pink.

Why was NaOH able to pass through the dialysis bag?

NaOH molecules are small enough to pass through the semipermeable membrane.

Which molecule crossed the dialysis bag when starch and iodine were used?

Iodine moved into the bag.

Why could iodine move but starch could not?

Iodine molecules are small, but starch molecules are too large to pass through the membrane.

How can you predict whether a dialysis bag will gain or lose weight?

Water moves from areas of low solute concentration to high solute concentration (osmosis).

In which direction does water move during osmosis?

From hypotonic (low solute) to hypertonic (high solute) areas.

What happened to the weight of the bag in the 25% sucrose (inside) vs 1% sucrose (outside) setup?

The bag gained weight as water moved into it (beaker → bag).

What does a hypertonic solution cause a cell or bag to do?

Lose water and shrink.

What does a hypotonic solution cause a cell or bag to do?

Gain water and swell.

What color is phenolphthalein in neutral solutions?

Colorless

What color is phenolphthalein in basic (alkaline) solutions?

Pink

What does a steeper slope on a dialysis bag weight vs. time graph indicate?

A faster rate of diffusion or osmosis.

Why did bag D (25% sucrose inside) gain weight faster than bag C (10% sucrose inside)?

The greater concentration difference created a steeper gradient and faster water movement.

What is diffusion?

Movement of molecules from high to low concentration until evenly distributed.

What is osmosis?

Diffusion of water through a semipermeable membrane from low to high solute concentration.

What is equilibrium?

The point when concentrations are equal and there is no net movement of molecules.

What happens to animal cells (RBCs) in a hypotonic solution (H₂O)?

They swell and may burst (hemolysis).

What happens to animal cells in a hypertonic solution (10% NaCl)?

They shrink (crenation).

What happens to animal cells in an isotonic solution (0.9% NaCl)?

They remain the same size—no net water movement.

What happens to plant cells (Elodea) in a hypotonic solution (H₂O)?

They become turgid (swollen but protected by the cell wall).

What happens to plant cells in a hypertonic solution (10% NaCl)?

The cell membrane pulls away from the wall (plasmolysis).

What happens to plant cells in an isotonic solution (0.9% NaCl)?

They stay the same; no net water movement.

What is the typical salt concentration inside animal cells?

Approximately 0.9% NaCl.

In which direction does water move relative to the cell?

Into or out of the cell depending on external solution tonicity.