This document discusses cell membrane transport, including the types of transport mechanisms cells use to move nutrients and molecules in and out. It describes diffusion, facilitated diffusion, and osmosis as passive transport mechanisms that move particles down concentration gradients without requiring energy. Active transport is defined as the active movement of particles against a concentration gradient, which does require energy in the form of ATP. Different osmotic environments are also defined based on the relative concentration of water inside and outside the cell.

1. BIOLOGY
Unit 2 Notes:
Cell
Membrane
Transport

2. (1) Cell Membrane Transport
• Why Do Cells Do This?
Cells need to move useful nutrients and
molecules in and out of the cell .
• Types of Transport:
– Diffusion
– Facilitated Diffusion
– Osmosis
– Active Transport

4. (2) Diffusion
• Movement of particles from high to low
concentration, across a concentration
gradient, until reaching equilibrium.
• Does NOT require any energy (or ATP).

6. (3) Facilitated Diffusion
• The assisted movement of large molecules
across protein channels, from high to low
concentration, until reaching equilibrium.
• Does NOT require any energy (or ATP).

8. (4) Osmosis
• The diffusion of water.
• The movement of water molecules from
high to low concentration, across a
gradient, until reaching equilibrium.
• Does NOT require any energy (or ATP).

10. (5) Osmotic Environments
• Isotonic Environment:
When there is an EQUAL concentration of water
inside, and outside the cell.
• Hypertonic Environment:
When there is a HIGHER concentration of water
inside the cell, than outside.
• Hypotonic Environment:
When there is a LOWER concentration of water
inside the cell, than outside.

11. (6) Active Transport
• The forced movement of particles, AGAINST
a gradient, from low to high concentration.
• Requires the use of energy (or ATP).