Rate of Osmosis and Transport Processes Investigation

Vocabulary terms and core concepts based on the osmosis and diffusion lab notes, including transport mechanisms, experimental variables, and microscopy calculations.

Osmosis Investigation Hypothesis

If the size of the potato cube increases, then the rate of osmosis will decrease because larger cubes have a smaller surface area-to-volume ratio.

Independent Variable (Potato Experiment)

The size of the potato cubes ($1 \times 1 \times 1\,\text{cm}$, $2 \times 2 \times 2\,\text{cm}$, and $3 \times 3 \times 3\,\text{cm}$).

Dependent Variable (Potato Experiment)

The percentage change in mass of the potato cubes.

Controlled Variables (Potato Experiment)

The volume of solution ($60\,\text{ml}$), the time kept in the solution (overnight), and the concentration of the sodium chloride solution ($5\%$).

Passive Transport

The movement of substances down their concentration gradient (from high to low concentration) without the use of cellular energy.

Active Transport

The movement of substances against their concentration gradient (from low to high concentration) requiring energy supplied by $ATP$ and the use of protein carriers.

Agar Cube Indicator Change

A color change that occurs when acidic vinegar diffuses into agar containing a pH indicator, showing how far the acid has spread.

Surface-Area-to-Volume Ratio ($SA:V$) Relationship

As a cube gets bigger, its volume increases faster than surface area, leading to a decrease in $SA:V$ and a slower overall rate of diffusion through the cube.

Isotonic Solution

A solution with the same solute concentration as the cell's cytoplasm, resulting in no net movement of water.

Hypotonic Solution

A solution with a lower solute concentration than the cell's cytoplasm, causing water to move into the cell by osmosis.

Hypertonic Solution

A solution with a higher solute concentration than the cell's cytoplasm, causing water to move out of the cell by osmosis.

Diffusion

The movement of particles from a region of higher concentration to a region of lower concentration until they are evenly spread out.

Osmosis

The movement of water molecules across a differentially permeable membrane from a region of higher water concentration (lower solute) to a region of lower water concentration (higher solute).

Differentially Permeable Membrane

A membrane that allows some substances to pass through freely while restricting the passage of others.

Concentration Gradient

The difference in the concentration of a substance between two areas.

Starch vs. Iodine Membrane Permeability

Iodine molecules are small enough to pass through membrane pores, whereas starch molecules are too large to pass through.

Field of View ($FOV$) Calculation

$$\frac{\text{Current magnification} \times \text{Current FOV}}{\text{New magnification}}$$

Size of one object Calculation

$$\frac{\text{FOV diameter}}{\text{Number of objects fitting across}}$$

Reliability (Investigation Limitation)

The degree of consistency in results; rated low in this experiment because only one trial was conducted per cube size.

Validity (Investigation Limitation)

The extent to which an experiment measures what it intended; rated moderate, but weakened by imprecise hand-cutting of potato cubes.