Diffusion

Diffusion is one of the key processes that allows substances to move into and out of cells. Imagine it as the natural "spreading out" of particles, like how the smell of freshly baked cookies spreads through a room.

 

What is Diffusion?

Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration. This process happens down a concentration gradient, meaning particles spread out to even things out.

Definition:

Diffusion is the movement of particles from a region of higher concentration to a region of lower concentration, caused by their random motion.

Example:

• Imagine putting a drop of food coloring in water. Over time, the color spreads out evenly without stirring.

• In biology, oxygen diffuses from the air into your blood because there’s more oxygen in the air than in your blood.

 

Diffusion in Cells

Diffusion happens across cell membranes to move substances like gases, nutrients, and waste in and out of cells. The cell membrane acts as a selective barrier, allowing certain particles to pass through.

 

 

• Cells directly use diffusion in order to get substances inside and out of the cell through the cell membrane
• The cell membrane of a cell acts as a partially permeable membrane. This means some molecules can pass through will others are not able to.
• Molecules can be filtered out based on the size of the molecule 

Substances that Move by Diffusion:

1. Oxygen: From the air in your lungs into your blood.

2. Carbon dioxide: From your blood into the air in your lungs.

3. Glucose and other nutrients: Into cells for energy.

 

Why is Diffusion Important?

Diffusion plays a critical role in keeping organisms alive. Here are some examples:

1. Gas Exchange:

   • In the lungs, oxygen diffuses into the blood, and carbon dioxide diffuses out.

2. Nutrient Absorption:

   • In the small intestine, nutrients like glucose diffuse into the blood.

3. Waste Removal:

   • Carbon dioxide and other waste products diffuse out of cells.