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17 Cards in this Set
- Front
- Back
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Biological Membranes |
Around all cells (prokaryotic and eukaryotic) and surrounding some cells e.g mitochondria. |
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Phospholipids |
They form the phospholipid bilayer section of the membrane. They are modified triglycerides with two fatty acid chains and one phosphate group. The phosphate head is hydrophilic and the non-polar tails are hydrophic. |
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Roles of the membrane |
Partially permeable barrier, site of chemical reactions and cell signalling. |
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Fluid Mosaic model |
This is used to describe the arrangement of molecules in the membrane, 'fluid' because the phospholipds are constantly moving and 'mosaic' because protein molecules are scattered. |
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Role of cholesterol |
Cholesterol is a component of membranes and is involved in maintaing stability and regulating fluidity. |
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High temperature effect on membrane |
The increased temperature is converted to kinnetic energy in the membrane so the phospholipds vibrate rapidly and the fluidity is increased. |
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Low temperature effect on membrane |
The lower temperature can cause the membrane to become more rigid and disrupt normal cell function. |
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Solvents effect on membrane |
Water is a polar solvent which allows the bilayer to form, organic solvents which are less polar/non-polar dissolve the membrane and disrupt the cell. |
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Diffusion |
The net movement of particles from a region of higher concentration to a region of lower concentration, this is a passive process meaning it does not require energy. |
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Factors affecting Simple Diffusion |
High temperatures lead to increased kinnetic energy so faster diffusion, and low temperatures slower. Large concentration gradients lead to faster diffusion, and small difference leads to slow diffusion. Large SA leads to fast diffusion and also a thin membrane leads to fast diffusion. |
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Diffusion across Membranes |
Occurs through the phospholipid bilayer if the membrane is permeable to the particles e.g non-polar. |
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Facilitated Diffusion |
Channel Proteins, polar molecules and ions can pass through. Carrier Proteins, if molecule is too large. |
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Active Transport |
Movement of molecules or ions from a region of lower concentration, to a region of higher concentration, using ATP. It is used to maintain concentration gradients and requires carrier proteins. |
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Bulk Transport |
A type of active transport for large quantites of objects e.g enzymes or hormones. Endocytosis- into the cell, Exocytosis - out of cell. |
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Osmosis |
The movement of water molecules from a higher water potential to a lower water potential. |
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Water potential |
The pressure exerted by water molecules as they collide with a membrane or container. More water leads to a higher water potential. Measured in Pa/kPa. |
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Cell Signalling |
The process by which cells communicate with each other. It allows multicellular organisms to control and coordinate their bodies and to respond to their environments. |
