9700 · 4.1
Fluid mosaic membranes flashcards
Revision flashcards for Cambridge 9700 Fluid mosaic membranes (syllabus 4.1). Flip, recall, then mark a real past-paper question.
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What are the two main components of the fluid mosaic model's name, and what do they represent?
'Fluid' represents the constant movement of phospholipids and proteins. 'Mosaic' represents the scattered pattern of proteins embedded within the phospholipid bilayer.
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Describe the structure of a phospholipid molecule.
It has a polar, hydrophilic (water-loving) phosphate head and two non-polar, hydrophobic (water-fearing) fatty acid tails. This makes it an amphipathic molecule.
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What is the primary function of cholesterol in an animal cell membrane?
Cholesterol acts as a fluidity buffer. It reduces fluidity at high temperatures and increases fluidity at low temperatures, maintaining membrane stability across a range of temperatures.
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Differentiate between intrinsic and extrinsic proteins.
Intrinsic (integral) proteins are embedded within the phospholipid bilayer (some span the entire membrane). Extrinsic (peripheral) proteins are loosely attached to the membrane's surface.
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What is the glycocalyx and what is its function?
The glycocalyx is a carbohydrate layer on the outer surface of the cell, formed by glycoproteins and glycolipids. It is involved in cell-cell recognition, adhesion, and as receptors.
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Name two types of transport proteins found in the cell membrane.
Channel proteins and carrier proteins. Channel proteins form hydrophilic pores for specific ions, while carrier proteins change shape to transport specific molecules.
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Why is the phospholipid bilayer described as 'selectively permeable'?
Because its hydrophobic core allows small, non-polar molecules to pass through freely but restricts the passage of large, polar, or charged substances, which require protein channels or carriers.
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How do unsaturated fatty acid tails affect membrane fluidity?
Unsaturated fatty acid tails have 'kinks' or bends due to C=C double bonds. These kinks prevent phospholipids from packing closely together, which increases the fluidity of the membrane.