A boundary that seperates the living cell from its non-living surroundings.
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What are the main features of the cell surface membrane?
It is selectively permeable, responsible for cell-cell recognition, allows compartmentalisation and allows transport(removing unwanted products from cell and required materials to the cell).
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How thick is the cell surface membrane?
7.5 nano-metres.
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What is meant by 'Selectively Permeable'?
The membrane controls movement of substances into and out of the cell.
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What is meant by 'Compartmentalisation'?
Where there are two membranes which isolate the reactions taking place inside them from those taking place elsewhere, eg mitochondria.
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What is the best model of the plasma membrane?
Fluid Mosiac Model.
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Why is it called a Fluid Mosaic Model?
Membrane is fluid because there is movement or diffusion of lipid molecules. These are protein within the membrane which look like a mosaic pattern.
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Who made the Fluid Mosiac Model and When?
Singer and Nicolson 1972.
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What are the components of the cell surface membrane?
Phospholipids, Phospholipid bilayer, Glycolipids, Glycoproteins, Intrinsic/Intergral Proteins, Extrinsic/Peripheral Protein and Cholesterol.
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Phospholipids
A phospholipid is made up a hydrophillic gylcerol and phosphate head, their heads have a tiny charge and this attratcs them to H20 molecules.They also have hydrophobic fatty acid tails attatched to the head, these do no have a charge and hate water.
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Phospholipid Bilayer
Made up of a continuous stack of Phospholipids, it is surrounded by the cytoplasm containg lots of water. Because the tails repel from H20, the phospholipids form a double layer with heads facing outwards and tails facing inwards.
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Glycolipid
A phospholipid molecule with a carbohydrate chain(glycocalyx) attatched to it. The gycocalyx allows cell-cell recognition and cell adhesion.
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Glycoprotein
A protein molecule with a glycocalyx attatched to it. Involved in cell-cell recognition and cell adhesion.
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Intrinsic/Integral Protein
These proteins span the membrane, act as channels or carriers for facilated diffusion/active transport. ALWAYS COME IN PAIRS.
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Extrinsic/Periphal Protein
Dont span the membrane, are found in both inside and outside of membrane. They act as receptors or enzymes.
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Cholesterol
Helps maintain the fluidity of the membrane and prevents it becoming to stiff when temperatures are low or too fluid when the temperatures are too high.
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What is meant by 'Cell-signalling'?
A receptor in the cells plasma membrane picks up a signal and causes a response within a cell.
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Why do cells use signalling molecules?
To gather information about the environment and respond to any changes in the environment and commuinicate with other cells.
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Other cards in this set
Card 2
Front
What are the main features of the cell surface membrane?
Back
It is selectively permeable, responsible for cell-cell recognition, allows compartmentalisation and allows transport(removing unwanted products from cell and required materials to the cell).
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