cell transport

• Cells interact with their environment
• Eukaryote cells have membrane-bound organelles
• Cells contain genetic material, cytoplasm, and ribosomes
• Phospholipid bilayer


  Consists of two layers of lipids, with polar heads and nonpolar tails
• Cell membrane


  A very important structure in ALL cells that helps regulate homeostasis by controlling what goes in and out
• Facilitated diffusion is a type of passive transport that involves transport proteins helping molecules pass through the membrane
• Simple diffusion


  Moves with the flow, following the concentration gradient from high to low concentration
• Glucose needs transport proteins to pass through the membrane
• Cells lining the gut need to take in glucose
• All mentioned transport processes are passive, moving from high to low concentration
• Cells must have control on what goes in and out to maintain homeostasis
• Organelles in cells have different functions
• Almost ALL cells, prokaryotes and eukaryotes, have genetic material, cytoplasm, and ribosomes
• The cell membrane is made of a phospholipid bilayer
• In osmosis, water passes through protein channels called aquaporins
• Simple diffusion allows molecules to pass through the phospholipid bilayer without the need for energy
• Charged ions often require protein channels for passage
• Transport proteins in the cell membrane

  • Act as channels
  • Change shape to facilitate movement
  • Open and close based on stimuli
• Facilitated diffusion moves with the concentration gradient from high to low concentration
• Active transport

  Movement of molecules from low to high concentration, requiring energy (typically ATP)
• Endocytosis


  Fusing of the cell membrane with large molecules to bring them inside the cell
• Exocytosis

  Molecules exiting the cell, used for getting rid of cell waste or important materials out of the cell
• Active transport


  • Can force molecules to go against their concentration gradient by energizing the transport protein itself
• Large carbohydrates are important for making plant cell walls


  Exocytosis is needed to get the carbohydrates produced in the plant cell out of the cell to make the wall
• Favorite example of active transport

  • Sodium-potassium pump
• ATP

  Adenosine triphosphate, a molecule with 3 phosphates. Energy is released when the bond for the last phosphate is broken
• Passive transport


  Movement of molecules from high to low concentration
• Types of endocytosis

  • Amoebas use a form where pseudopods stretch out around substances to engulf them and pull them into a vacuole
  • Receptor-mediated endocytosis where incoming substances have to bind to receptors to enter
  • Pinocytosis which allows the cell to take in fluids