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. |