Cell transport

• Cells contain genetic material, cytoplasm, and ribosomes, which are found in both prokaryotes and eukaryotes
• Eukaryote cells have membrane-bound organelles with different functions
• Cells interact with their environment and must have some control on what goes in and out to maintain homeostasis
• Cell membrane


  A very important structure that all cells contain to control what goes in and out, helping regulate homeostasis
• Cell membrane


  • Made of a phospholipid bilayer
  • Part of the lipids have polar heads and nonpolar tails
• Simple diffusion


  1. Small non-polar molecules like gases can directly pass through the phospholipid bilayer

  2. Moves with the concentration gradient from high to low concentration

  3. Requires no energy (passive transport)
• Facilitated diffusion


  1. Transport proteins in the membrane help larger or polar molecules cross the membrane

  2. Still moves with the concentration gradient from high to low concentration

  3. Requires no energy (passive transport)
• Transport proteins


  Some act as channels, some change shape, some open and close based on stimuli, to help molecules cross the membrane
• Charged ions and glucose require transport proteins to cross the cell membrane
• Water crosses the membrane rapidly through protein channels called aquaporins
• Active transport


  Movement of molecules from low to high concentration, requiring energy (typically ATP)
• The sodium-potassium pump is an example of active transport
• Endocytosis


  1. Cell membrane fuses with large molecules to bring them into the cell, often forming vesicles

  2. Different types include phagocytosis, pinocytosis, and receptor-mediated endocytosis
• Exocytosis


  1. Molecules exit the cell, including waste and important materials the cell has produced

  2. Used to secrete materials like plant cell wall polysaccharides
• Cell walls are different from cell membranes and not all cells have walls
• Nucleus


  The nucleus is the largest organelle in the cell and is where the cell's DNA is stored. It is the site of genetic material transcription and protein synthesis.
• Mitochondria


  Mitochondria are the "powerhouses" of the cell and are responsible for generating energy in the form of ATP through a process called cellular respiration.
• Endoplasmic reticulum (ER)


  The ER is a network of tubules and sacs where proteins and lipids are synthesized and modified. The ER has two parts: the rough ER, which has ribosomes on its surface and is involved in protein synthesis, and the smooth ER, which is involved in lipid synthesis and detoxification.
• Golgi apparatus


  The Golgi apparatus is a series of membrane-bound compartments that modify, sort, and package proteins and lipids for transport to their final destinations.
• Lysosomes


  Lysosomes are membrane-bound organelles that contain enzymes for breaking down and recycling waste materials within the cell.
• Vacuole


  The vacuole is a membrane-bound organelle that stores water, nutrients, and waste products.
• Facilitated diffusion


  A type of passive transport that uses transport proteins to help larger or polar molecules cross the cell membrane down their concentration gradient
• Transport proteins


  Specialized proteins embedded in the cell membrane that have a specific shape to bind to certain molecules and help them cross the membrane
• Concentration gradient


  The difference in concentration of a substance between two areas, with higher concentration at one end and lower concentration at the other end
• Passive transport


  The movement of molecules across a membrane from an area of high concentration to an area of low concentration without the input of energy