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1.4 IB Bio

Membrane Transport

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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