CELL MOVEMENTS Part 2 of Slide Presentation over

CELL MOVEMENTS Part 2 of Slide Presentation over Cells

� Matter exists in one of three physical states: 1. Solid � 2. Liquid � 3. Gaseous � � Kinetic Energy of motion - collisions �A solid has minimal kinetic energy and has closely packed atoms. � A liquid has more dispersed atoms with greater kinetic energy � A gas has a very low density and the atoms are in vigorous motion.

� Passive Methods Active Methods

• Factors affecting the rate of diffusion include � � � Solubility Molecular Size Temperature State of Matter Gradient

� � Dialysis is the movement of solutes through a membrane by diffusion. Membrane must be permeable

� � � Concentration Gradient Energy requirement is missing Uses molecular movements � folding � rotation � domain � shape changes Glucose absorption in the liver

� � � Movement of water through a membrane Diffusion is basic mechanism Water concentrations � Solute concentration � Solvent concentration � � � Hyper-osmolarity Iso-osmolarity Hypo-osmolarity

� Initial condition • Water and Solute move along gradients

� Equilibrium state - compromise � Osmotic Pressure

� � Hyper-tonic Hyper-osmotic Isotonic Iso-osmotic Hypo-tonic Hypo-osmotic

� � � Osmosis - Driving force is water concentration Diffusion - Driving force is concentration gradient Filtration - Driving force is pressure � Force of material - gravity � Pressure - Hydralic � � � Selectivity - size along Solvent drag Bulk transport

� � The two principal differences between the passive movement of materials across membranes and the active movement of materials In active movements: � Against the concentration gradient. � Use of. metabolic energy. The conversion of ATP to ADP with the release of energy The conversion of kinetic energy to chemical energy which occurs when ions move down ion gradients.

� � � Antiport type active transport system called the Sodium/Potassium Linked Pump. Uses &% total energy It uses approximately 7% of the total energy of the body Moves Sodium out of cell Moves Potassium into cell

� Here can be seen the antiport protein with three active sites for sodium ions and two for potassium ions. A phosphate has been added to the protein by the conversion of ATP to ADP. Sodium ions are moving into the active sites for transport.

� The Channel protein opens to the inside of the cell. The three sodium ions are loaded into the active site and the energy released from the ATP - ADP reaction causes a shape change in the channel protein.

� The protein does a flip/flop and now opens to the outside of the cell. The sodium ions are now free to diffuse outward into the extracellular space.

� Sodium now moves out of the active sites and away from the membrane. Simultaneously the potassium moves into their sites. The channel remains open because of the phosphate which has been attached to the channel protein.

� The phosphate is removed from the protein after the potassium has occupied the sites and the channel reverts its' shape back to its original form.

� � � The channel protein now again open towards the inside of the cell. The potassium moves into the cytosol while new sodium ions enter the channel to begin the cycle again. No energy for K+ movement Energy needed for Na+ movement

� • Exocytosis where vesicles with the cytosol fuses with the plasma membrane to expel the contents of the vesicle to the outside. This mechanism is particularly important in nerve impulse transmission.

� � � There are two general types of endocytosis: Pinocytosis Phagocytosis.

� � In Phagocytosis, the process can be made more efficient when the particles to be ingested are tagged with specific proteins which will interact with receptors located on the plasma membrane. As an example, often invading bacteria are tagged with specific antibodies (1). White blood cells are preprogrammed to react

� to these bacteria because their membranes have receptors specific to the antibody tags. When the labeled bacteria comes into contact with the receptors, pseudopods (2) are produced which surrounds the bacteria forming a vesicle into which a lysosome (3) can be added to promote the destruction (4) of the bacterium. This digestive process will continue until the debris (5) remaining can be absorbed into the cytosol.

• Receptor Medidated Endocytosis involves the binding of extracellular molecules with spedific receptors on the plasma membrane, causing the membrane to invaginate and draw � those molecules into a coated intracellular vesicle. An example of this type of active transport is the binding of Low Density Lipids or Ligands to and LDL receptor protein located on the surface of a plasma membrane.

• Receptor Medidated Endocytosis involves the binding of extracellular molecules with specific receptors on the plasma membrane, causing the membrane to invaginate and draw � those molecules into a coated intracellular vesicle. An example of this type of active transport is the binding of Low Density Lipids or Ligands to and LDL receptor protein located on the surface of a plasma membrane.

� � � Property of all living cells Inside of cell is Negative to outside of cell Potential is maintained by ion levels and Sodium/Potassium pump Cell is Polarized Threshold IPSP EPSP