Biology

Lab Notes

Diffusion

The process of molecules moving from an area of higher concentration to an area of lower concentration.

Diffusion continues until it is evenly distributed across the space.

The rate is affected by temperature, size of molecules, and the steepness of the concentration gradient

1. Density of medium

2. Concentration gradient

3. Temperature

4. Molecular Size

5. Membrane permeability

• Defined as the net movement of particles form an area of higher concentration to an area of lower concentration. Resulting from the random movement of molecules.

Solute vs Solvent

Solute is what dissolves in the solvent . Like the substance Salt

Solvent is the substance that holds the solute to be dissolved in , like water. The solute is typically in lesser quantity compared to the solvent, which is present in greater quantity and dissolves the solute.

**In biological systems like the cytoplasm or blood, the solvent is blood.

Concentration Gradient

A concentration gradient exists when solute concentrations are unequal within a solution. —Diffusion only occurs in a place where there is a concentration gradient

Selectively Permeable

This means to allow some substances to pass while preventing others from doing so. A membrane is given this title if it does as such.

Cell Membrane factors

Non charged molecules pass through by Simple Diffusion , without help from a transport protein

• Small solutes that are charged or polar are blocked by the membrane, so their passing through requires a transport protein. This is called Facilitated Diffusion .

So, factors would be its charge or polarness.

Solutions

A solution is a homogenous(parts are equal and uniform) mixture of at least two substances

• Major component is the solvent

• Minor component(s) are the solutes

• A simple example would be salt dissolved in water.

Concentration

The concentration of a solution is a measure of the amount of solute that dissolved in a certain amount of solvent

• Example - a solution with 10 grams of salt dissolved in 1 liter of water has concentration of 10 grams/liter

A solution with a large amount of solute is concentrated, whereas a solution with little solute is dilute

Diffusion Rate Through Different Media

Substances diffuse faster within media that are less dense (more space to move)

• With all factors being equal. diffusion rate of a substance is slowest in a semi solid, faster in liquid, and fastest in air.