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18 Cards in this Set
- Front
- Back
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Plasma membrane functions |
-Encloses the cell, isolates its contents from the external environment -regulates flow of substances in and out of the cell -allows communication with other cells |
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Phospholipids |
-Responsible for isolating isolating the internal from the external environment
-Proteins regulate the exchange of materials as well as interactions with the environment |
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Fluid mosaic model |
Protein molecules are arranged in the phospholipid like tiles in a mosaic |
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The structure of the membrane is maintained because |
-Phospholipid consists of a polar hydrophilic containing a phosphate group
-It also contains a pair of non-polar hydrophobic fatty acid tails |
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Intrinsic proteins |
Embedded inside the protein |
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Extrinsic proteins |
Found attached outside the protein |
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gylcoprotein |
Some membrane proteins have carbohydrates attached to them |
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Different types of membrane proteins: |
Transport proteins: Intrinsic, transport molecules across cell membranes Recognition proteins: glycoproteins enable cells of body's defence system to recognise foreign cells Receptor proteins: have specific binding sites where hormones or other chemicals can bind triggering particular cellular responses Catalytic proteins: Enzymes which control chemical reactions Structural proteins: involved in maintaining the shape of the cell |
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Cholesterol |
-Makes the phospholipid bilayer more flexible by disturbing the close packing of phospholipids -Cells in the body are continuously changing shape as an organism moves -If plasma membranes weren't flexible they'd snap with every slight movement |
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Selectively permeable |
Membrane can select some substances to pass through |
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How can materials cross membranes? |
-Simple diffusion -Osmosis -Facilitated diffusion -Active transport |
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Simple diffusion |
-A few substances can pass directly through the membrane, because the membrane can't act as a barrier since they're so small (oxygen and carbon dioxide)
- Diffusion is the movement of molecules from region of high concentration to a region of low concentration until they become equally distributed |
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Osmosis |
The movement of water molecule from a dilute solution to a concentrated solution across a selectively permeable membrane |
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Solute Solution |
-Solution is the water diluted with the solute |
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Facilitated diffusion |
- Diffusion is the movement of molecules from region of high concentration to a region of low concentration, across a membrane
-They do this with the help of intrinsic transport proteins
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Transport proteins: channel proteins |
Channel proteins: -form a permanent water-filled channel in the membrane which allows water-soluble substances such as ions to pass through
The channel has a fixed diameter specific for a particular type of protein
Most channels have gates that control the entry and exit of these molecules |
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Transport proteins: carrier proteins |
- have binding sites for specific solutes -When molecules bind to the protein, the protein changes shape so that the molecules can are carries across the membrane |
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Active transport |
The movement of molecules from a region of low concentration to a region high concentration, wit the help of carrier protein and energy from ATP |
