Cell Transport

• All cells have a cell membrane which controls what enters and exits the cell to maintain an internal balance called homeostasis.
• The structure of a cell membrane consists of a Lipid Bilayer which consists of two layers of phospholipids.
• The phosphate head of a phospholipid is polar (water loving) while the fatty acid tail is non-polar (water fearing).
• Salt water fish pump salt out of their specialized gills so they do not dehydrate.
• Kidneys keep the blood isotonic by removing excess salt and water.
• Animal cells are bathed in blood.
• Proteins are embedded in the membrane.
• Cell membranes have pores (holes) in it which are selectively permeable, allowing some molecules in and keeping other molecules out.
• The structure of the cell membrane helps it be selective.
• Passive transport is a process where the cell uses no energy and molecules move randomly, spreading out from an area of high concentration to an area of low concentration.
• Passive transport has three types: Diffusion, Facilitative Diffusion, and Osmosis.
• Diffusion is a process where molecules move randomly from an area of high concentration to an area of low concentration until equilibrium is reached.
• Facilitative Diffusion is a process where diffusion occurs with the help of transport proteins.
• Osmosis is a process where water moves from an area of high concentration to an area of low concentration until equilibrium is reached.
• Active transport is a process where the cell uses energy, with three types: Protein Pumps, Endocytosis, and Exocytosis.
• The Sodium Potassium Pump pumps three sodium ions out of the cell and two potassium ions into the cell.
• A hypotonic solution has a lower concentration of solutes and a higher concentration of water than inside the cell, resulting in water moving from the solution to inside the cell, causing the cell to swell and burst open (cytolysis).
• Endocytosis is a type of active transport that takes bulky material into a cell, uses energy, and forms a food vacuole to digest food.
• Osmosis is the diffusion of water through a selectively permeable membrane, and water is so small that the cell can't control its movement through the cell membrane.
• An isotonic solution has the same concentration of solutes as inside the cell, resulting in water moving equally in both directions and the cell remaining the same size (dynamic equilibrium).
• Exocytosis is a type of active transport that forces material out of the cell in bulk, requires energy, and causes the cell to change shape.
• Organisms deal with osmotic pressure by having cell walls that prevent them from over-expanding, like bacteria and plants, or by having contractile vacuoles that collect water flowing in and pump it out to prevent them from over-expanding, like paramecium.
• A hypertonic solution has a higher concentration of solutes and a lower concentration of water than inside the cell, resulting in water moving from inside the cell into the solution, causing the cell to shrink (plasmolysis).
• Facilitated diffusion is the diffusion of specific particles through carrier proteins found in the membrane.
• Active transport involves movement from an area of low concentration to an area of high concentration.
• Passive transport also involves diffusion in the lipid bilayer.
• Passive transport involves facilitated diffusion through carrier proteins.
• Facilitated diffusion transports larger or charged molecules.
• Osmosis is the diffusion of water through a selectively permeable membrane.
• Active transport involves three types of transport proteins: protein pumps, carrier proteins, and ion channels.
• Water moves freely through pores in osmosis.
• Osmosis is a type of passive transport.
• Passive transport can involve transport proteins such as channel proteins.
• Facilitated diffusion is a type of passive transport that involves channel proteins.
• Solutes are unable to move across the membrane in osmosis.
• Active transport involves the use of energy and it actively moves molecules to where they are needed.
• Carrier proteins are specific and they "select" only certain molecules to cross the membrane.
• Protein pumps are transport proteins that require energy to do work, for example, Sodium/Potassium Pumps are important in nerve responses.
• Water moves from high to low concentrations in osmosis.