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21 Cards in this Set
- Front
- Back
Why was the name 'fluid mosaic model' given? |
• Fluid means that the phospholipids are constantly moving. • Mosaic describes the arrangement of the molecules in the membrane. |
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What does the fluid mosaic model of the cell membrane look like? |
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Explain the roles for phospholipids and cholesterol. |
• Phospholipid - Have a hydrophilic head and hydrophobic tail. The centre of the bilayer is hydrophilic because the membrane doesn't allow water-soluble substances to allow pass through it. Small, non-polar substances and water can diffuse through it. • Cholestrol - gives the membrane stability because it binds to the tails of the phospholipids, causing them to pack closely which restricts movement. |
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How do temperatures affect the membrane permeability? |
• Temperatures below 0°c - The phospholipids can't move a lot. The channel and carrier proteins in the membrane denature increasing the permeability. Ice crystals may form and pierce the membrane, making it highly permeable when it thaws. • Temperatures between 0°c and 45°c - they can move around more. As the temperature increases the phospholipids move more because they have more energy, increasing the permeability. • Temperatures above 45°c - The bilayer melts down. Water inside the cell's expands. The carrier and channel proteins denature so they can't control what leaves or enters the cell. Which evidently increases the permeability. |
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How can you investigate the cell membrane permeability? |
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What is diffusion? |
It is the net movement of particles from an area of high concentration to an area of low concentration. It moves down a concentration gradient. |
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What is simple diffusion? |
When molecules diffuse directly through a cell membrane. |
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Name some factors that can affect diffusion. |
• Concentration gradient - The higher it is, the faster diffusion will be. This will lead up to both sides of the membrane being in equilibrium; diffusion slows over time. • Thickness of exchange surface - thinner the exchange surface, the quicker the diffusion is because they'd have a shorter distance. • Surface area - Larger means diffusion will happen quicker. |
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What is facilitated diffusion? |
Net movement of particles from a high concentration to a low concentration, using carrier proteins (carries large molecules) and channel proteins (carries charged particles). |
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Name factors affecting the rate for facilitated diffusion. |
• Concentration gradient - higher concentration gradient means that the faster the rate of diffusion is. • Number of channel or carrier proteins - if all of the proteins are occupied then that means facilitated diffusion can't happen any quicker. |
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What is osmosis? |
Diffusion of water molecules across a partially permeable membrane, from an area of higher water potential to an area of low water potential. |
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What is the water potential of pure water? |
Zero |
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What does it mean if cells are in a ... solution: • Isotonic • Hypertonic • Hypotonic |
• Isotonic - Two solutions have the same water potential. • Hypertonic - Solutions with lower water potential than the cell. • Hypotonic - Solutions with high water potential than the cell. |
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Name some factors affecting the rate of osmosis. |
• Water potential gradient - higher the gradient, faster the rate of osmosis. • Thickness of exchange surface - thinner exchange surface, faster the rate of osmosis. • Surface area of the exchange surface - Larger surface area means more quicker osmosis occurs. |
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How would you make serial dilutions? |
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How does active transport work? |
• It uses energy (gained by hydrolysing ATP) to move molecules and ions across plasma membranes, usually against a concentration gradient. Carrier proteins and co-transporters are involved in active transport. |
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Two main differences between facilitated diffusion and active transport? |
• Active transport requires energy. • Active transport usually moves solutes from a low concentration to a high concentration. |
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How is glucose absorbed in the lumen? |
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Factors affecting the rate of active transport? |
• Speed of individual carrier proteins - faster they work, the faster the rate of active transport. • Number of carrier proteins present - more proteins there are, the faster the rate of active transport. • The rate of respiration into he cell and the availability of ATP. If respiration is inhibited, active transport can't take place. |
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What is the function of glycolipids and glycoproteins? |
• Glycolipids - help maintain stability, help cells attach to one another and act as recognition sites. • Glycoproteins - act as recognition sites, help cells attach to one another and allow cells to recognise one another. |