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25 Cards in this Set
- Front
- Back
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What is the fluid mosaic model? |
A model which shows the arrangement of molecules in the membrane |
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Why is the cell membrane fluid and mosaic |
Fluid - phospholipids are constantly moving Mosaic - proteins are scattered through bilayer |
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What is present within fluid mosaic model? |
Phospholipids Proteins Cholesterol Glycolipids Glycoproteins |
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What is the role of phospholipids in cell membrane? |
Molecules arrange themselves into a bilayer Hydrophilic heads face outwards and hydrophobic tails are inside Centre of bilayer is hydrophobic so water soluble substances can get through it - acts as a barrier |
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What is the role of cholesterol in the cell membrane? |
Cholesterol molecules bind to the hydrophobic tails of the phospholipids, causing them to pack more closely together, this restricts the movement of phospholipids, making the membrane less fluid and more rigid Cholesterol helps to maintain the shape of animal cells |
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How does a temperature of below 0 affect membrane permeability? |
Phospholipids don't have much energy so can't move much They're packed closely together and membrane is rigid but channel and carrier proteins in membrane deform, increasing permeability of the membrane
Ice crystals may form and pierce the membrane making it highly permeable when it thaws |
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How does a Temp of between 0-45 affect membrane permeability? |
Phospholipids can move around and aren't packed as closely together - membrane is partially permeable As temp increases phospholipids move more, this increases permeability of membrane |
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How does a temp above 45 affect membrane permeability? |
Phospholipids bilayer starts to Melt and membrane becomes more permeable Water inside the cell expands, putting pressure on the membrane Channel proteins and carrier proteins deform so they can't control what enters and leaves the cell This increases permeability of membrane |
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What is diffusion? |
The net movement of particles from an area of higher concentration to an area of lower concentration This continues until particles have reached equilibrium Diffusion is a passive process |
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What is simple diffusion? |
When molecules diffuse directly through a cell membrane |
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What particles are transferred through facilitated diffusion? |
Larger molecules (eg amino acids and glucose) Charged particles (eg ions and polar molecules) |
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What is facilitated diffusion? |
Molecules diffuse through cell membrane with the help of carrier proteins or protein channels It moves particles down a Concentration gradient from higher to lower concentration It is a passive process |
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Describe carrier proteins |
Move large molecules across membranes, down their concentration gradient - a large molecule attaches to a carrier protein in the membrane - then the protein changes shape - this releases the molecule on the opposite side of the membrane |
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Describe co-transporters |
They are a type of carrier protein They bind two molecules at a time, the concentration of one of the molecules is used to move the other molecules against its own concentration gradient |
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What factors affect the rate of active transport? |
The speed of individual carrier proteins the faster they work, the faster the rate of active transport Number of carrier proteins present the more proteins there are the faster the rate of active transport The rate of respiration in the cell and the availability of ATP if respiration is inhibited, active transport can't take place |
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How is glucose absorbed into the blood? |
Co-transport in the mammalian ileum with sodium ions |
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Describe channel proteins |
Form pores in the membrane for charged particles to diffuse through Different channel protein facilitate he diffusion of different charged particles |
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What factors affect the rate of simple diffusion? |
Concentration gradient the higher if is the faster the rate of diffusion Thickness of exchange surface the thinner the exchange surface the faster the rate of diffusion The surface area the larger the surface area the faster the rate of diffusion |
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What factors affect the rate of facilitated diffusion? |
Concentration gradient the higher the concentration gradient the faster the rate of facilitated diffusion Number of channel or carrier proteins the greater the number the faster the rate of diffusion |
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What is osmosis? |
The diffusion of water molecules across a partially permeable membrane from an area of higher water potential to an area of Lower water potential |
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What is water potential? |
The likelihood of water molecules to diffuse out of or into a solution |
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What word describes to solution with the same water potential? |
Isotonic |
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What affects the rate of osmosis? |
Water potential gradient the higher the water potential the faster the rate of osmosis Thickness of exchange surface the thinner the exchange surface the faster the rate of osmosis Surface area of exchange surface the larger the surface area the faster the rate of osmosis |
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What is active transport? |
Uses energy to move molecules and ions across membranes usually against a concentration gradient Involves carrier proteins |
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What are the differences between active transport and facilitated diffusion? |
Active transport usually moves solutes from a low to high concentration, in facilitated diffusion they always move from a high to low concentration ATP requires energy - facilitated diffusion does not |
