Grade 12 Cell Transport PDF

Cell Membrane Transport Mechanism Subtitle  Cell Membrane Transport Mechanism Passive Transport is the diffusion of a substance across a biological membrane, needing no input of energy. – Simple Diffusion simply refers to the movement of molecules of any substance wit...

Cell Membrane Transport Mechanism Subtitle  Cell Membrane Transport Mechanism Passive Transport is the diffusion of a substance across a biological membrane, needing no input of energy. – Simple Diffusion simply refers to the movement of molecules of any substance with regards to the concentration gradient (from the region of high concentration to low concentration).  Passive Transport – Osmosis refers to the diffusion of free water across a selectively permeable membrane, whether artificial or cellular. Water diffuses across the membrane from the region of lower solute concentration (higher free water concentration) to that of higher solute concentration (lower free water concentration) until the solute concentrations on both sides of the membrane are equal.  Osmosis – Tonicity refers to the ability of a surrounding solution to cause a cell to gain or lose water and is greatly influenced by the concentration of solutes that cannot cross the membrane relative to the solute concentration inside the cell.  Cell Membrane Transport Mechanism Passive Transport is the diffusion of a substance across a biological membrane, needing no input of energy. – Simple Diffusion simply refers to the movement of molecules of any substance with regards to the concentration gradient (from the region of high concentration to low concentration).  Passive Transport –Facilitated diffusion refers to the diffusion of substances which requires specific structure such as proteins and also does not need energy for the transport process.  Two Types of Facilitated Diffusion Channel proteins are transport proteins which serves as a hydrophilic tunnel for certain atoms or molecules. – Aquaporins are channel proteins that enables the passage of water molecules through the cell membrane and increases the transport rate of water. – Ion channels are channel proteins that transport ions and mostly function as gated channels, which open or close in response to a stimulus. Carrier proteins are also transport proteins that hold onto their passengers and change shape in a way that transports them across the membrane. – Glucose transporter a specific carrier protein in the plasma membrane of red blood cells that transports glucose across the membrane  Cell Membrane Transport Mechanism Active Transport is the type of membrane transport that requires the cell to expend energy. This type of transport need the energy to move materials across the concentration gradient. – Membrane potential is the voltage across a membrane which acts as a battery or an energy source that affects the movement of charged substances across the membrane. – combination of forces acting on ions is called the electrochemical gradient. – Co-transport refers to the process in which the membrane protein enables the “downhill” diffusion of one solute to drive the “uphill” transport of another.  Active Transport sodium-potassium pump which exchanges Na+ for K+ across the cell membrane.  Bulk Transport Bulk Transport refers to the mechanism used by large molecules such as proteins and polysaccharides and other large particles crossing the membrane in bulk (packaged in vesicles. This process also requires energy. – Two Types of Bulk Transport – Exocytosis- used by secretory vesicles in cells to export cellular Exocytosis in a cell membrane products.  Bulk Transport Endocytosis-cells take in molecules and other materials by forming new vesicles from plasma membrane. Types of Endocytosis – Phagocytosis (“cellular eating”)- cell engulfs a particle by extending pseudopodia around a particle and packaging it using the membranous sac called food vacuole.  Types of Endocytosis Pinocytosis (“cellular drinking”)-the cell “drinks” drops of extracellular fluid into small vesicles. The molecules dissolved in the droplets are taken by the cell.  Types of Endocytosis Receptor-mediated endocytosis- cell acquires bulk quantities of particular substances that were not concentrated in the extracellular fluid.