3. MOVEMENT INTO AND OUT OF CELL

Transport Mechanisms Overview

• Three primary transport mechanisms:

  1. Passive Transport

  2. Osmosis

  3. Active Transport

Passive Transport

• Diffusion

  You can see particles moving from a high concentration to a low concentration area to achieve equilibrium (concentration is equal). This is how oxygen and carbon dioxide move in and out of cells.

  Example = oxygen & carbon dioxide movement

  

• Osmosis

  Water moving from a high water potential to a low water potential across a partially permeable membrane. Osmosis allows water particles to pass, blocks larger particles and applies to both animal and plant cells. This process affects animal and plant cells differently - animal cells can burst or shrivel, while plant cells become turgid or flaccid.

  

Effects of Osmosis

Animal Cells

• High Water Potential

  • Water enters cell

  • Potential cell expansion/bursting

• Low External Water Potential

  • Water exits cell

  • Cell shriveling possible

Plant Cells

• High Water Potential

  • Water enters cell

  • Cell becomes turgid

  • Cell wall prevents bursting

• Low Water Potential

  • Water exits cell

  • Potential plasmolysis

  • Plant wilting occurs

Active Transport

Active Transport is the movement of particles from a low concentration to a high concentration. Movement of molecules/ions against concentration gradient. Requires energy from cellular respiration.

Example = root hair cells & human small intestine

Active & Passive Transport