3.5 Passive Transport vs. Active Transport Passive Transport: requires NO energy. Diffusion (dialysis and osmosis) Facilitated diffusion Active Transport: requires energy Active Transport Endocytosis/Exocytosis

Diffusion and Osmosis require no energy (Passive Transport)

Passive Transport Some molecules are too large to fit through the phospholipid bilayer. They can only diffuse through proteins. (This is still Passive Transport.) Facilitated diffusion is diffusion through proteins in the cell membrane. Example: glucose

Active transport occurs through protein pumps. Active transport uses energy to move things against its concentration gradient. Active transport occurs through protein pumps. Energy allows the protein to change shape and pump molecules against the concentration gradient

Active Transport: Sodium/Potassium Pump For Example: For nerve cells to function properly, there must be a higher concentration of Na outside and higher concentration of K inside the cell

Sodium Potassium Pump (See animation)

Endocytosis and Exocytosis If the material is too large to move through the protein, it must enter/exit in a different way. Endocytosis (material entering cell) Examples: food into amoeba, white blood cells Steps: Material surrounded by cell membrane Vesicle pinches off from cell membrane Vesicle enters cell, contents are released Empty vesicle digested by lysosome

Endocytosis

Moving material out of the cell. Exocytosis Exocytosis Moving material out of the cell. Examples: protein exported, nerve cells Steps: Material in the cell is packaged by the Golgi Vesicle joins with the cell membrane Contents are dumped outside the cell and the membrane closes back up

Exocytosis