- Slides: 15
Transport Passive and Active
Passive Transport Passive transport is any transport that occurs without the use of energy. ¨ Ex: ¨ ¤ Diffusion ¤ Osmosis ¤ Facilitated diffusion ¤ Ion Channels
Diffusion The movement of molecules from an area of higher concentration to an area lower concentration. ¨ Concentration gradient ¨ Driven by kinetic energy ¨ Dynamic equilibrium ¨ CO 2 and O 2 ¨
Osmosis ¨ ¨ The process in which water molecules diffuse from areas of higher concentration to lower concentration. Depends on the concentration of the solutes found in the water on the two sides of the membrane.
Isotonic When the concentration of solutes outside and inside the cell are equal, the outside solution is said to be isotonic to the cell. ¨ The water moves into and out of the cell at even rates. ¨ Iso- equal / the same
Hypotonic When the concentration of solute is lower outside of the cell than the concentration of solute inside the cell. The solution outside the cell is said to be hypotonic. ¨ The water will move into the cell until equilibrium is reached. ¨ Hypo – under / beneath
Hypertonic Hyper – above / excessive When the concentration of solute is higher outside of the cell than the concentration of solute inside the cell. The solution outside the cell is said to be hypertonic. ¨ The water will move out of the cell until equilibrium is reached. ¨
Cells and Osmosis ¨ ¨ Contractile Vacuole – organelle that takes up water from the cytoplasm and then pump it out of the cell. Requires energy. Turgor Pressure – pressure that water molecules exert against the cell wall. Plasmolysis – When plant cells do not receive enough water and the cell membrane shrinks away from the cell wall. The plant cell shrivels. Cytolysis – When animal cells are left in hypotonic solutions, water continues to enter until the cell bursts.
Tonicity ¨ ¨ Tonicity problems let you figure out how water will diffuse based on the % concentration of a solution. Ex: ¤ If the solution in a cell is 2% solute, it would be 98% water. That cell is placed in a solution that was 5% solute and therefore 95% water. n Is the solution that the cell is placed in hypotonic, isotonic, or hypertonic? n Is the cell going to gain or lose water? n If the cell is an animal cell, what would the cell look like after it sat in the solution for an extended period of time?
Facilitated Diffusion and Ion Channels ¨ ¨ Facilitated diffusion – movement of molecules across a membrane with assistance from proteins in the membrane. Energy is still not being used. ¤ Performed by carrier proteins (type of integral protein) ¤ Aid in movement from higher concentration to lower concentration regardless of movement into or out of the cell. ¤ Glucose uses carrier proteins Ion Channels ¤ ¤ Transport ions from higher concentration to lower concentration Na+, K+, Ca 2+, and Cl. Specific for each ion Gated
Active Transport Movement of molecules from lower concentrations to higher concentrations with the use of energy. ¨ Ex: ¨ ¤ Cell Membrane Pumps ¤ Movement in vesicles (small spherically shaped sacs surrounded by a single membrane) n Endocytosis n Exocytosis
Cell Membrane Pumps ¨ Carrier proteins that use energy to “pump” molecules from one area to another. ¨ Use energy – ATP (Adenosine Triphosphate) ¨ Ex : Na+ /K+ Pump ¨ Need a higher concentration of Na+ outside the cell and a higher concentration of K+ inside the cell. ¨ ¨ ¨ 3 Na+ bind to the pump inside the cell, the pump expels them outside of the cell. This builds up a high concentration of Na+ outside the cell. The pump then binds 2 K+ located outside the cell and pushes them through the membrane into the cell. This creates an electrical gradient across the cell where the inside of the cell is negative in comparison to the outside. ¤ Allows for the sending and receiving of electrical impulses across the cell.
Na+/K+ Pump 13
Endocytosis When substances are brought into the cell ¨ There are two types ¨ ¤ Pinocytosis - small particles and fluid ¤ Phagocytosis - large particles or entire cells n Used by cells as a way to eat n Used by the immune system to take in bacterial cells and dead tissues/debris to be destroyed by the lysosome
Exocytosis The process by which the cell exports materials out of the cell. ¨ Items for export are first packaged in the Golgi apparatus ¨ Releases items such as: proteins, hormones, waste, or toxins ¨