Movement of Cells In and Out: Factors Affecting Diffusion Rate

Vocabulary flashcards covering the factors that affect the rate of diffusion (concentration gradient, distance, temperature, and surface area to volume ratio) as well as the experimental methods and calculations used to investigate diffusion in a non-living agar system.

Concentration Gradient

The difference in concentration between two regions; a higher concentration gradient results in a higher rate of diffusion.

Diffusion Distance

The physical distance between two regions; less distance between regions results in a higher diffusion rate, while greater distance results in a lower diffusion rate.

Temperature (Diffusion Effect)

A factor that affects diffusion by altering kinetic energy ($\text{K.E}$); higher temperature increases kinetic energy, causing the rate of diffusion to increase.

Surface Area to Volume Ratio

The amount of surface area exposed per unit of volume; smaller substances have a larger surface area to volume ratio leading to faster diffusion, whereas larger substances have a smaller ratio leading to a decreased diffusion rate.

Membrane Folding

A structural adaptation in living bodies, such as in the intestine, that increases the surface area to volume ratio for efficient absorption of substances.

Branching (Biological Surface Area)

A structural adaptation in living systems, such as root hairs, that increases surface area to volume ratio.

Vascular Networking

A structural arrangement where blood vessels branch into capillaries between arteries and veins, increasing the surface area to volume ratio in living organisms.

Agar

A jelly-like substance used for growing cultures of bacteria, utilized in different cube sizes to investigate diffusion rates in a non-living system.

Phenolphthalein (Agar Indicator)

A pH indicator that turns pink in the presence of an alkaline solution such as sodium hydroxide ($NaOH$) and becomes colourless when neutralized by hydrochloric acid ($HCl$).

Potassium Permanganate ($KMnO_4$)

A chemical substance that imparts a purple colour to agar and becomes colourless when neutralized by hydrochloric acid ($HCl$).

$0.5 \times 0.5 \times 0.5\,\text{cm}$ Agar Cube

The smallest agar cube size tested, having a surface area of $1.5\,\text{cm}^2$, a volume of $0.125\,\text{cm}^3$, and the largest surface area to volume ratio of $12:1$, which causes it to turn colourless first.

Timed Decolourization Method (Diffusion)

An experimental method to measure diffusion rate by recording the time required for an agar cube to become completely colourless as acid diffuses into it.

Distance Measurement Method (Diffusion)

An experimental method to measure diffusion rate by using a ruler to measure the distance in millimeters ($\text{mm}$) that acid has diffused inward from the cube edges after a set period of time (e.g., after $2\,\text{min}$ or $3\,\text{min}$).

Experimental Limitation (Agar Cube Investigation)

The technical constraint requiring agar blocks to be cut precisely using a proper ruler and a scalpel.