Fluid Mosaic Model BBC Education - AS Guru - Biology - Cells - Pathways - Plasma MembranesBBC Education - AS Guru - Biology - Cells - Pathways - Plasma Membranes
Proteins in Membrane
Cholesterol: add stability to membrane in higher temperatures
Carbohydrate Chain: Used as Identification Markers
PROTEIN JOBS: attaches to cytoskeleton
PROTEIN JOBS: Enzymes which are catalytic teams for molecular assembly lines A Biochemical Pathway (click on animation)A Biochemical Pathway Biochemical Pathway Animation II (CLICK- ALSO CLICK ON ARROWS)Biochemical Pathway Animation II
PROTEIN JOBS-Receptors: enable cells to detect chemical messages from other cells
PROTEIN JOB: Signal Transduction Receptor binds to trigger a chain reaction EXAMPLE ANIMATION (CLICK ON START AND NEXT) MAP Kinase Signal Transduction Animation by Dr. Vic Lemas at BioCreationsMAP Kinase Signal Transduction Animation by Dr. Vic Lemas at BioCreations Another Signal Transduction Animation Interactive Concepts in Biochemistry - Interactive Animations Interactive Concepts in Biochemistry - Interactive Animations
Signal Transduction Diagram
Diffusion Movement of a substance from a region of higher concentration to a region of lower concentration
Facilitated Diffusion A protein helps the substance (like an ion) across the membrane
Facilitated Transport Facilitated diffusion involves the use of a protein to facilitate the movement of molecules across the membrane. Cell Animations (scroll down to Carrier- mediated passive transport Facilitated transport)Cell Animations
Passive Transport Cell does not need to use energy Movement of molecules goes “down the gradient” (from high to low concentration) –Diffusion –osmosis –Facilitated diffusion
Active Transport During active transport, cell needs to use energy (ATP) as molecules against a concentration gradient (low concentration to high concentration). –endocytosis –Exocytosis –Pumps (USE ATP) Cell Animations (scroll down to active transport)Cell Animations
Comparing Active and Passive Transport Shockwave Click hereShockwave
Endocytosis The process by which a cell engulfs material to bring it into the cell is called endocytosis. A vacuole is formed that contains the material that has been engulfed.
Exocytosis Vesicle fuses with plasma membrane to exit the material outside the cell (cell pooping)
Endocytosis Animation Endocytosis and Exocytosis Animation What is the difference between the two? Which brings material in and which brings materials out of the cell? Endocytosis is in Exocytosis is out
Diffusion: flow from high to low concentration Also facilitated diffusion (protein channel)
Things that can pass freely through the plasma membrane Hydrophobic molecules (oil soluble) O 2 N 2 Nonpolar Benzene Small uncharged Polar molecules H 2 O CO 2
Molecules that don’t pass through the phospholipid bilayer easily... Large uncharged Glucose Polar molecules Sucrose Ions (charged) H +, Na +, HCO 3, K +, Ca +2,Cl -, Mg +2
So what three characteristics of a molecule determine the permeability of the membrane? Charge Size Polarity
However: some molecules which we would think should (or should not) cross the plasma membrane do - (or don't) because of the presence of the membrane proteins.
Osmosis Osmosis is the movement of water from a region of high water concentration to a region of lower water concentration through a selectively permeable membrane. The Cell: Passive Transport Osmosis - Learning - clickThe Cell: Passive Transport Osmosis - Learning -
Solution Vocabulary Solute- what is being dissolved EX: salt Solvent – what is doing the dissolving EX: water Solution = solvent + solute
Hypotonic Solution Osmosis (click for animation)Osmosis A hypotonic solution is one that has less solute (more water). Cells in hypotonic solution tend to gain water.
Isotonic Solution Osmosis (click for animation)Osmosis the concentration of solute is the same on both sides of the membrane (inside the cell and outside). A cell placed in an isotonic solution neither gains or loses water. Most cells in the body are in an isotonic solution.
Drag the bag Osmosis (predict what will happen)Osmosis LabBench (do a little experiment)LabBench
Hypertonic Solution Osmosis (click for animation)Osmosis A hypertonic solution is one that has a high solute concentration. Cells in a hypertonic solution will lose water.
Plasmolysis Plant cells placed in a hypertonic solution will undergo plasmolysis, a condition where the plasma membrane pulls away from the cell wall as the cell shrinks. The cell wall is rigid and does not shrink. before
Osmosis Lab Use grams on the scale. Be very careful when carrying (use a spoon) and drying the egg (gently with a paper towel). Two set-ups per lab table. (If one side breaks, you have a back-up.) WHEN FINISHED: Clean beakers. Dry off scale and turn off.
Plasmolysis of Elodea Also scroll down for rehydration of elodea Watch the chloroplasts
Plant Cell Plasmolysis Stiff Cell wall Plasmolysis: Flaccid: Turgid: Sunken in Normal pressure Lots of pressure Cell wall on cell wall on cell wall
Can you tell which is the plasmolyzed and which is normal elodea?
Compare Plant Cells NORMAL CELL Plasmolysis
water moves toward the area with a higher solute concentration because it has a lower water concentration.
water moves from hypotonic to hypertonic solution.
Red Blood Cells p. 83
Solutions If a cell is in a Hypotonic solution, the cell will… lose water If a cell is in a Hypertonic solution, the cell will… gain water
Turgor: pressure of water vacuole on the cell wall of a plant
Active Transport Active Transport Animation Cell needs energy to move particles “against the gradient” - from low to high concentration
"pumps" materials across the membrane against the concentration gradient. i.e.,from low concentration to high concentration (therefore it requires energy).
Endocytosis Endocytosis: Large materials transported into the cell. Endocytosis includes three slightly different processes: –Phagocytosis –Pinocytosis –Receptor-mediated
Endocytosis Endocytosis - "to enter the cell" Phagocytosis - large particles - membrane "reaches out" - phago = eat" Pinocytosis - solutes in fluids - membrane folds in to form a pouch known as a vesicle. - pino = drinking" Receptor mediated endocytosis - receptors on the membrane attach to large molecules like hormones and folds them inside.
Pinocytosis “Cell drinking” Engulfing small liquid droplets
Receptor-Mediated Endocytosis Receptor Mediated EndocytosisReceptor Mediated Endocytosis Specialized receptor that just fits a specific substance EX: LDL Hormones insulin
Receptor Mediated Endocytosis
Exocytosis Material (wastes etc.) are expelled from the cell
Table 8.2: Five processes by which substances move across cell membranes. Particle Protein Energy Movement Carrier Required Simple High to low No No Diffusion Facilitated Diffusion High to low Yes No Active Transport Low to high Yes Yes Exocytosis Intracellularl to extracellular No, occurs by fusion of vesicles with cell membrane. Endocytosis Extracellular to intracellular No, occurs by involution of cell membrane.