Materials Move Across Cell’s Membranes

1. Materials Move Across Cell’s Membranes Chapter 2.3C

2. Review • What is a cell membrane?? • What is the purpose of a membrane? • What are membranes primarily made up of? • For the remainder of the powerpoint, copy words highlighted in ORANGE!

3. Diffusion • Molecules spread out from where there are many to where there are fewer • They keep spreading until they are evenly distributed • Examples: • Smelling a scent • Oxygen (needed for respiration) and carbon dioxide (produced by respiration)

4. Concentration • The number of particles of that substance in a specific volume • Example: • Dissolving 9 grams of sugar in 1 liter of water yields the concentration 9g/L

5. Diffusion in Cells • Materials are able to move into and out of the cell • Example: • Photosynthesis: • produces oxygen inside the cell • Concentration of oxygen is higher on the inside than the outside • Oxygen cells move out of the cell by diffusion **What are some daily examples of diffusion?

6. Types of Diffusion • Passive transport • Active transport • Osmosis • Endocytosis • Exocytosis

7. Passive Transport • Materials move without using the cell’s energy (moving from high concentration to low concentration)

8. Osmosis • Diffusion of water through a membrane • Example: • Unwatered plants wither • Water leaves the plant’s roots to go to the dry soil to even out the concentration of water molecules • When the plant is watered, water molecules diffuse through the plant’s cell membranes to even out the concentration again

9. Active Transport • Process of using energy to move materials through a membrane (moving from low concentration to high concentration) • Examples: • Marine iguanas • Kidneys

10. Endocytosis • Moving materials too large to pass through a membrane INTO the cell • Membrane folds inward, creating a pocket • Membrane closes around the material, forming a “package” • “Package” breaks away from cell membrane, bringing the material into the cell

11. Exocytosis • Moving materials too large to pass through a membrane OUT OF the cell • “Package” carries materials to cell membrane • Attaches to membrane and merges together • Materials are pushed out of membrane

12. Cell Size (and shape) Affects Transport • As cell grows, surface area is not large enough to allow resources to travel to all parts of cell • As a result, the cell may: • Stop growing • Divide • Shape • Thin and flat cells (single-celled organisms) have increased surface area • Long and skinny cells (nerve and muscle) have increased surface area