Table Of Contents: Osmosis and Diffusion: Cell Transport
1. Cell Transport
2.1. Cell Membrane
Each cell is surrounded by a cell membrane which provides structure and controls the passage of materials between the cell and its environment.
2.2. Cell Membrane Composition
A cell membrane consists of two layers composed of proteins and lipids.
2.3. Semi-Permeable Cell Membrane
A cell membrane is known as a semi-permeable membrane since it only allows certain substances to move into and out of the cell.
3.1. Function of Diffusion
Organisms use the process of diffusion to allow useful molecules to enter the cells and remove waste products.
3.2. What Is Diffusion?
Diffusion is the movement of a gas or solute molecules from an area where there are many to an area where there are few until they spread evenly throughout a space. This movement can occur across a cell membrane or outside of cells.
3.3. Oxygen Diffusion in the Lungs
For example, the high concentration of oxygen in the lung’s air sacs moves to a lower concentration in the blood while carbon dioxide moves from an area of high concentration in the blood to a lower concentration in the air sacs.
3. Osmosis - The Diffusion of Water
4.1. Importance of Osmosis
All cells need water to carry out life functions.
4.2. What Is Osmosis?
Osmosis is the diffusion of water through a cell membrane from a higher water concentration (dilute solution) to a lower water concentration (more concentrated solution).
4. Pause and Interact
Use the whiteboard text tool to complete the activity: How do molecules diffuse in a cell?
5. Passive and Active Transport
6.1. What Is Passive Transport?
The transport of materials across the cell membrane from an area of high concentration to an area of low concentration without the use of energy is called passive transport.
6.2. Facilitated Diffusion
Sometimes proteins are used to carry large molecules across a cell membrane. This process is called facilitated diffusion.
6.3. What Is Active Transport?
Some substances move across the cell membrane from an area of low concentration to an area of high concentration with the use of energy. The transport of materials through proteins in the cell membrane using energy is called active transport.
6.4. Active Transport in Plant Roots
An example of active transport is when plant root cells take in minerals from the surrounding soil. Because plant root cells typically have more minerals inside of them than the soil surrounding the roots, they use active transport to take in minerals from the soil.
6. Pause and Interact
Use the whiteboard text tool to complete the activity: How does a cell take in and push out large particles?
7. Vocabulary Review
8.1. Vocabulary Matching Review
8. Virtual Investigation
9.1. Viewing Osmosis in Action
In this virtual investigation you will observe the effects of different concentrations of water on plant (onion) cells and animal (blood) cells. Select the type of cell you would like to observe and then use the slide bar to see the effects of pure, normal and salt water.