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Exchange with the Environment

Exchange with the Environment. Essential Question. How do materials move across the cell membrane?. The exchange of materials between a cell and its environment takes place at the cell ’ s membrane. In a living thing, the cell membrane is permeable - allows materials to pass through it.

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Exchange with the Environment

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  1. Exchange with the Environment

  2. Essential Question How do materials move across the cell membrane?

  3. The exchange of materials between a cell and its environment takes place at the cell’s membrane. • In a living thing, the cell membrane is permeable - allows materials to pass through it. • Because the cell membrane only permits substances such as food, oxygen, and water to diffuse into the cell, it is said to be selectively permeable.

  4. Materials enter and leave a cell through a variety of methods • Passive Transport • Diffusion (simple) • Facilitated Diffusion • Osmosis • Active Transport • Endocytosis • Exocytosis

  5. Passive Transport • movement of materials through a membrane from high concentration to low concentration. • This type of movement does not require energy

  6. Diffusion The process by which molecules of a substance move from areas of higher concentration (more of the molecules) of that substance to areas of lower concentration (fewer of the molecules) of that substance.

  7. Diffusion • Diffusion occurs whether matter is in the form of a gas, liquid, or solid.

  8. Osmosis • a special type of diffusion where water moves into or out of a cell in order to travel from an area of higher concentration to lower concentration.

  9. Diffusion and Osmosis do not require energy. • The movement just happens whenever there are unequal concentrations inside and outside a cell.

  10. Diffusion through a membrane Cell membrane Outside cell Inside cell

  11. Diffusion through a membrane Cell membrane diffusion Outside cell Inside cell

  12. Diffusion through a membrane Cell membrane Outside cell Inside cell EQUILIBRIUM

  13. Movement of Small Particles • Many particles because of their small size, such as water and oxygen, can diffuse directly through a cell membrane; however, other particles must travel through protein “doorways” located in the cell membrane. Amino acids and sugar are 2 examples of items that travel through proteins. • Particles can travel through these doorways either by facilitated diffusion or active transport.

  14. Active Transport • movement of particles through proteins against the normal direction of diffusion. • Particles are moved from an area of lower concentration to higher concentration. • The cell must use energy to make this happen

  15. Moving Larger Particles • Diffusion, passive transport and active transport are good methods of moving small particles; however, the cell also has two ways of moving larger particles.

  16. Endocytosis • the cell membrane surrounds a particle and encloses it in a vesicle.

  17. Exocytosis • vesicles are formed at the ER and the Golgi complex to carry the particles to the cell membrane

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