2Cell or Plasma Membrane Composed of double layer of phospholipids and proteins (phospholipid bilayer)Surrounds outside of ALL cellsControls what enters or leaves the cellLiving layerOutsideof cellInside(cytoplasm)CellmembraneProteinsProteinchannelLipid bilayerCarbohydratechainscopyright cmassengale
3copyright cmassengale PhospholipidsHeads contain glycerol & phosphate and are hydrophilic (attract water)Tails are made of fatty acids and are hydrophobic (repel water)Make up a bilayer where tails point inward toward each otherCan move laterally to allow small molecules (O2, CO2, & H2O to enter)copyright cmassengale
4Cell Membrane Proteins Proteins help move large molecules or aid in cell recognitionPeripheral proteins are attached on the surface (inner or outer)Integral proteins are embedded completely through the membranecopyright cmassengale
6The Cell Membrane is also referred to as the Fluid Mosaic Model Molecules in cell membranes are constantly moving and changingcopyright cmassengale
7Structures Of The Plasma Membrane Phosphate Head: Made of a phosphate group (polar and attracts water)Carbohydrate: Used for cell recognitionMembrane Protein: Transports large particles across the cell membraneCholesteral: Helps stabilize the phospholipidsLipid Tails: Made of fatty acids (non-polar and does not attract water)
11Diffusion● Concentration gradient: the difference in concentration across a barrier/membrane● Because diffusion depends upon random particle movements, substances diffuse across membranes without requiring the cell to use energy
15Dynamic Equilibrium Equal concentrations are reached Not the same volumesContinued movement across the membraneNot gain or loss
16Osmosis● Osmosis is the diffusion of water through a selectively permeable barrier. Water will tend to move across the membrane until equilibrium is reached, when this occurs the two solutions will be isotonic, the same.● When a solution is more concentrated with solute it is said to be hypertonic, whereas a dilute (less concentrated) solution is said to be hypotonic.Pre-AP do the potato experiment with salt waterDiscuss osmotic pressure as a side discussion to the second question. For Pre AP may wish to perform potato lab with regular tap water and salt water.
24Passive Transport Cell uses no energy From high to low Plasma membrane Concentrationgradient
25Facilitated Diffusion Type of passive transportUse transportproteinsChannel proteinsCarrier proteinsChanges shapeFrom high to low
26Facilitated Diffusion ● During facilitated diffusion molecules that would not normally be able to cross through the membrane, such as glucose, diffuse across the membrane through selected protein channels.It is dependent upon the concentration gradient because it does not require the cell to expend any energy.
28Active Transport Cell uses energy Against concentration gradient From low to highCarrier ProteinsMolecule binds with carrier proteinEnergy then used to change shapeMolecule released on other sideCarrier protein returns to original shape
29Active Transport●The movement of material across a membrane and against a concentration gradient is called active transport.Like facilitated diffusion this is carried out by protein channels in the membrane called transport proteins, however in this form of diffusion energy is expended in the process of “pumping” the material “uphill” against the gradient.
31Large Particle Transport ● Endocytosis is the process of taking material into the cell by means of enfolding's, or pockets, of the cell membrane. The pocket or enfold, once it has surrounded the molecule, then closes and breaks off from the membrane forming a vacuole. Two examples of endocytosis are phagocytosis (cell eating) and pinocytosis (cell drinking).● Exocytosis works the opposite of endocytosis. It is a vacuole with material designated to leave the cell which joins with the cell membrane then releases its material outside of the cell.
32Large Particle Transport (Exocytosis and Endocytosis)
33Large Particle Transport Not through membraneRequires energyExocytosis- out