1. Diffusion Aim: How does diffusion occur through a semi-permeable membrane?   Objectives: 1-Define the word diffusion & passive transport. 2-Explain the concept of diffusion & passive transport.

2. Vocabulary development:
1-Gradient = is the difference of measurement between two side or end.
2-Passive transport = to transport an object without applying energy.
3-Semi-permeable = not everything can pass through it, but is selective of the things that can pass through it.

3. 4-Membrane = acts as a barrier and controls and / or regulate what enters and leaves in a cell.
5-Diffusion = is the ability to transport an object from an area of high concentration to an area of low concentration without applying energy.
6-Equilibrium = When the situation equally balance and/or stable.

4. Mechanism for Crossing the Membrane Barrier
Passive Diffusion
Simple diffusion is the movement of a substance from a place of high concentration to one of lower concentration without applying energy for this reason it is called “passive transport”.

6. Analyze the diagrams and explain the direction or exchange of gas flow in the lungs of a human, by writing a paragraph or more with your partner(s). Attention should be noted that the oxygen gas (O2) is 90% and carbon dioxide gas (CO2) is 45% in the alveolus of the lung. Also, the blood vessel called capillary contains 45% oxygen gas (O2) and 90% carbon dioxide gas (CO2) in the red blood cell.
The flow of air in and out of the alveoli of the lung is called ventilation and has two stages: inspiration (or inhalation) and expiration (or exhalation).