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| Question | Answer |
| What are the functions of membranes at the cell surface? | Partially permeable Substances can move across by diffusion, osmosis or active transport Allow recognition by other cells Cell communication/cell signalling |
| What are the functions of membranes at within cells? | Act as a barrier between the organelle and the cytoplasm Forms vesicles to transport substances between different areas of the cell Partially permeable Membranes within organelles acts as barrier between the membrane contents and the rest of the organelle Site of chemical reactions |
| What is the fluid mosaic model? | This model states that membranes are composed of a phospholipid bilayer with various protein molecules floating within it |
| What does the 'fluid' part of the fluid mosaic theory suggest? | The 'fluid' part represents how parts of the membrane can move around freely, if they are not attached to other parts of the cell |
| What is the difference between intrinsic and extrinsic proteins? | INTRINSIC = completely spans the membrane EXTRINSIC = found only on the inner or outer surface of the membrane |
| Complete the sentences: The proteins also have _________ and ____-_________ regions. Weak __________ bonds between the _______ regions of the proteins and the phospholipids keep the membrane __________. | The proteins also have POLAR and NON-POLAR regions. Weak HYDROGEN bonds between the POLAR regions of the proteins and the phospholipids keep the membrane STABLE. |
| What are the components of cell membranes in the fluid mosaic model? |
Cholesterol
Carrier/channel proteins
Receptor proteins
Glycolipids
Glycoproteins
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| What is the role of cholesterol in the fluid mosaic model? | A steroid Can fit between the phospholipid molecules, increasing the rigidity and stability of the membranes as a whole They bind to the hydrophobic tails of the phospholipids, causing them to pack more closely together Cholesterol has hydrophobic regions, so it is able to create a further barrier to polar substances |
| What is the role of carrier/channel proteins in the fluid mosaic model? | Assists and controls the movement of water-soluble ions and certain molecules across the membrane |
| What is the role of receptor proteins in the fluid mosaic model? | Recognises and binds with specific molecules outside the cell, such as hormones and drugs When a molecule binds to the protein, a chemical reaction is triggered inside the cell |
| What is the role of glycolipids in the fluid mosaic model? | Lipids that have combined with polysaccharides and are thought to play a role in cell-to-cell recognition |
| What is the role of glycoproteins in the fluid mosaic model? | This is a combination of a protein and a polysaccharide Important in cells recognising each other Act as sites of cell communication (cell signalling) |
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