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1.4 IB Bio
Membrane Transport
| Term | Definition |
|---|---|
| Membrane permeability (Cell membranes are selectively permeable) | -This means that some substances (water, oxygen, carbon dioxide) can pass through the membrane freely -Other substances (proteins, ions) cannot pass through through the membrane and instead must pass through membrane protein channels |
| Transport across cell membranes chart | N/A |
| Isotonic | A solution of equal solute concentration to other solutions |
| Hypertonic | A solution of higher concentration to other solutions |
| Hypotonic | A solution of lower solute concentration to other solutions |
| Diffusion | The passive movement of particles from a region of high solute concentration to low solute concentration (down the concentration gradient) |
| Osmosis | The passive movement of water molecules, across a partially permeable membrane, from a region of lower solute concentration to a region of higher solute concentration -Particles don't move water does |
| Tissues or organs to be used in medical procedures must be bathed in a solution to prevent osmosis | -Intravenous drips use saline (0.9% salt solution) not distilled water -Organs and tissues need to be placed in saline to prevent swelling or desiccation |
| Dynamic equilibrium | -The number of particles moving into the cell is equal to the number of particles moving out of the cell |
| Simple Diffusion | -Particles cross directly through the membrane -Particles are small and uncharged |
| Facilitated Diffusion | -Travelling through special transport proteins -Particles match the shape and charge requirements to fit through the channels provided in the transport proteins |
| Passive Transport | -Does not require energy -Molecules move down the concentration gradient -Examples; Simple diffusion, facilitated diffusion and osmosis |
| Active Transport | -Requires energy (ATP) -Molecules move up the concentration gradient -Examples; membrane pumps, bulk transport using vesicles |
| How Active Transport works | -Sometimes a cell needs a substance to be moved against its concentration gradient -Integral proteins called protein pumps do this for specific molecules -ATP can be used to change the shape of a protein, allow it to move molecule across membrane |
| Endocytosis | -A vesicle is formed by the enfolding of the plasma membrane (in the cell) -Liquids and dissolved particles move by pinocytosis -Large particles move by phagocytosis |
| Exocytosis | -Vesicle membrane fuses with the plasma membrane(outside of cell) -Steps to exocytosis; Protein synthesis, Transport in vesicles, modification, transport to membrane, exocytosis |
| 1.Protein Synthesis | rER produces proteins which travel through the lumen of the ER |
| 2.Transport in vesicles | Membranes produced by the rER flows in the forms of transport vesicles to the golgi, carrying proteins within the vesicles |
| 3.Modification | Golgi apparatus modifies proteins produced by the rER |
| 4.Transport to membrane | Golgi pinches off vesicles that contain modified proteins and travel to plasma membrane. |
| 5. Exocytosis | Vesicles then fuse with plasma membrane, releasing their contents by exocytosis |
| Lipids | -Move latterly in a membrane, flip-flopping across the membrane is rare -Unsaturated hydrocarbon tails of phospholipids have kinks that keep the molecules from packing together, enhancing membrane fluidity. |
Created by:
averyschwarz
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