Biology: Cell Transport

Cell Transport

The movement of materials into and out of cells and around the cell.

What are the two types of cell transport?

Active transport and passive transport.

Active Transport

The movement of materials that requires ATP (energy).

Passive Transport

The movement of materials that does not require ATP (energy).

Diffusion

The movement of molecules from an area of higher concentration to an area of lower concentration.

Why does diffusion occur?

Because of probability, molecules naturally spread from areas of higher concentration to lower concentration.

What is the concentration gradient in diffusion?

Molecules move down their concentration gradient, from high concentration to low concentration.

What types of molecules can diffuse directly through the phospholipid bilayer?

Small nonpolar molecules, such as oxygen (O2) and carbon dioxide (CO2).

Can small polar molecules pass through the phospholipid bilayer?

Some small polar molecules, such as water (H2O), can pass through to a limited extent.

What molecules cannot easily diffuse directly through the phospholipid bilayer?

Large polar molecules, such as sugars (glucose and fructose) and proteins.

Osmosis

The movement of water molecules from an area of higher water concentration to an area of lower water concentration across a selectively permeable membrane.

What is a selectively permeable membrane?

A membrane that allows certain substances to pass through while preventing others from passing through.

Isotonic Solution

A solution that has the same dissolved particle (solute) concentration as the cell.

What happens to a cell in an isotonic solution?

There is no net water movement because water moves into and out of the cell at equal rates.

Dynamic Equilibrium

A state in which substances continue moving in both directions, but there is no net change.

Hypertonic Solution

A solution that has a higher dissolved particle (solute) concentration than the cell.

What happens to a cell in a hypertonic solution?

Water moves out of the cell, causing the cell to lose volume and shrink.

What happens to a red blood cell in a hypertonic solution?

It loses water and shrivels up.

Hypotonic Solution

A solution that has a lower dissolved particle (solute) concentration than the cell.

What happens to a cell in a hypotonic solution?

Water moves into the cell, causing it to swell and potentially burst.

What happens to a red blood cell in a hypotonic solution?

It takes in water, swells, and may burst.

What is the difference between isotonic, hypertonic, and hypotonic solutions?

Isotonic: same solute concentration; hypertonic: higher solute concentration outside the cell; hypotonic: lower solute concentration outside the cell.

In which direction does water move during osmosis?

From higher water concentration to lower water concentration.

What does ATP provide for active transport?

The energy needed to move materials.

Does passive transport require energy?

No, passive transport does not require ATP.