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Warm Up

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Presentation Transcript

  1. Warm Up • What is meant by concentration gradient? Which direction do materials diffuse across the gradient? • What is passive transport? • What are two examples of passive transport?

  2. 3.5 Active Transport, Endocytosis, and Exocytosis

  3. Moving against the concentration gradient • Cells need some materials that cannot passively diffuse across the membrane • Proteins can help transport materials against the concentration gradient. • These proteins are often called pumps

  4. Active Transport • Drives molecules across a membrane from a region of lower concentration to higher concentration (opposite of passive transport, different from facilitated diffusion) • Uses transport proteins • Requires energy • Allows cells to get necessary materials regardless of concentration gradient

  5. Transport Proteins • Found in membrane • Most change shape when they bind to a specific molecule • What do we call a change in shape? • Some bind to only one type of molecule, some bind two different kinds • Those that bind two may move both types in the same direction or in opposite directions

  6. Transport Proteins: key point • Using energy to move molecules against the concentration gradient • Most use energy from a molecule called ATP (adenosine triphosphate) • In what ways are active transport proteins similar to enzymes?

  7. Vesicles • A cell can use energy to move a large substance or large amount of a substance in a vesicle • Allows substances to enter/exit a cell without crossing through the membrane

  8. Endocytosis • Large molecules or liquids are engulfed by the membrane • Something like a little capsule forms • The capsule breaks off inside of the cell forming a vesicle • Vesicle fuses with lysosome which breaks down the membrane capsule and allows contents to be released into cell

  9. Phagocytosis • Type of endocytosis • Literally means “cell eating” • Key role in immune system • Macrophages are special white blood cells that perform an interesting form of phagocytosis • Video: watch the macrophage engulf invaders

  10. Exocytosis • Opposite of endocytosis • Release of substances from cell by way of a vesicle fusing with the membrane • Example: every move you make! • nerve impulses travel along nerve cells as an electrical signal • This electrical signal must be converted into a chemical signal to jump the small gap between nerve cells • These chemicals are stored in vesicles • Video clip: endocytosis and exocytosis

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