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vor etwa 9 Jahre
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Frage | Antworten |
Cell Membrane | Separate cells from environment. Allow cells to create internal compartments to maximize efficiency (compartments=organelles) Very specific about what substances they allow to cross them. |
Factors that cell membranes are fussy about | - size - polarity - charge Small molecules with no charge cross most easily. Large and/or charged particles are tightly regulated. |
Fluid mosaic model | The molecules that make up the cell membrane move around continuously. Proteins and other molecules bob around in the bi-layer. Called fluid mosaic model because fluid: movement and mosaic: interspersed with proteins and other molecules. |
Structure of cell membrane | Phospho-lipid bilayer interspersed with other molecules. |
Phospholipid Bi-layer | Hydrophilic head- turns and faces the outside- attracted to water. Hydrophobic tail, faces the middle. |
Simple Diffusion | Particles move from an area of high concentration to an area of low concentration. Small, uncharged particles are able to use this method. Does not require energy |
Facilitated Diffusion | Similar to simple diffusion except that the particles move through transport/carrier protein to reach the other side. Particles tend to be larger and more polar or charged. Still move down the concentration gradient. no energy required. |
Active Transport | Particles must move through transport proteins. Move against conc. gradient., DOES require energy in the form of ATP. |
Endocytosis | Movement of large particles or bulk quantities into a cell. part of cell membrane forms a vesicle around a particle then moves into cytosol. REQUIRES energy. |
Exocytosis | Bulk transport out of cell, requires energy |
Osmosis | Movement of water molecules from an area of low solute concentration to an area of high solute concentration. Does NOT require energy |
Solution gradient forms |
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