Diffusion, Osmosis & Active Transport

Diffusion

Net movement of particles from an area of higher concentration to an area of lower concentration

Osmosis

Diffusion of water molecules through a partially permeable membrane from high water potential to low water potential

Active transport

Movement of particles from low concentration to high concentration using energy

Concentration gradient

Difference in concentration between two areas

Partially permeable membrane

Membrane that allows some molecules to pass through but not others

Water potential

Measure of how much water a solution contains

Energy (ATP)

Required for active transport

Carrier proteins

Membrane proteins that move substances during active transport

What direction does diffusion occur in?

From high concentration to low concentration

Does diffusion require energy?

No

What factors increase the rate of diffusion?

Higher temperature, larger surface area, steeper concentration gradient

What is osmosis?

Movement of water from high water potential to low water potential through a partially permeable membrane

Does osmosis require energy?

No

What happens to an animal cell in pure water?

It bursts (lysis)

What happens to a plant cell in pure water?

It becomes turgid

What happens to a plant cell in a concentrated solution?

It becomes plasmolysed

What happens to an animal cell in a concentrated solution?

It shrinks (crenates)

What direction does active transport occur in?

From low concentration to high concentration

Does active transport require energy?

Yes, from respiration (ATP)

Why do root hair cells use active transport?

To absorb mineral ions from the soil against the concentration gradient

Which process uses carrier proteins?

Active transport

Which process moves water only?

Osmosis

Which process moves any particles that can diffuse?

Diffusion

Which process can move substances against the concentration gradient?

Active transport

Which process is fastest when the concentration gradient is steep?

Diffusion

Which process stops when the cell runs out of energy?

Active transport