Cell membranes 2 What is The Fluid Mosaic model of a cell membrane?
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Transcript of Cell membranes 2 What is The Fluid Mosaic model of a cell membrane?
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Cell membranes 2
What is The Fluid Mosaic model of a cell membrane?
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Success criteria
• I can describe the fluid mosaic model of the cell membrane structure with the aid of diagrams.
• I can describe the roles of the components of the cell membrane– Phospholipid– Cholesterol– Glycolipids– Proteins– glycoproteins
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Components of the fluid mosaic.What do you know about this?
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Key words – what are these things?
–Glycolipids–glycoproteins– Cholesterol– Proteins
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Glycoproteins and glycolipids
• Glyco – carbohydrates (sugars)
• So these are carbohydrate chains attached to proteins(glycoprotein)
• or attached to phospholipids (glycolipid).
These are used for signalling
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Key words – what are these things?
– Glycolipids– glycoproteins
–Cholesterol– Proteins
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Cholesterol
• Cholesterol is very important in SOME EUKARYOTIC cells for providing stability.
• IT is a steroid molecule that fits between the fatty acid tails forming a barrier and meaning water molecules and ions cannot pass easily through the membrane.
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Key words – what are these things?
– Glycolipids– glycoproteins– Cholesterol
–Proteins
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Proteins
• Extrinsic and intrinsic – what do these mean?
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Role of proteins
• They may act as enzymes eg carbohydrase enzymes are found in the cell membranes of intestinal epithelial cells.
• They act as receptors for hormones.• They act as carrier proteins, controlling what
enters and leaves the cell.• Carbohydrates and lipids attached to proteins
(forming glycolipids and glycoproteins) , allow cells to recognise one another.
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The fluid mosaic model of the plasma membrane:
The proteins can move freely through the lipid bilayer.
The ease with which they do this is dependent on the number of phospholipids with unsaturated fatty acids in the phospholipids.
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Fat-soluble organic molecules can diffuse through the bilayer but polar molecules require proteins
Extracellular space
Cytosoplasm (aqueous)
Fat-soluble molecules Polar molecules
hydrophilic pore
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There are different types of carrier proteins in the membrane:
ATP
Channel proteinGated-channel proteinCarrier protein(passive)
Carrier protein(active)
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Channel proteins
These provide a pathway for polar or large particles to move through the membrane.
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Carrier proteins
• These actively pump molecules into cells.• These use ATP energy
• E.g pumping Mg2+ ions into root hair cells,
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Question 4: How can polar and non-polar molecules pass through the membrane (2).
•Polar molecules require proteins to enable them to pass through the membrane
•Non-polar molecules can diffuse directly through the phospholipid bilayer
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The membrane contains many types of protein:
glycoprotein
carbohydrate chain
integral proteinperipheral protein
carrier protein
Glycocalyx: For cell recognition so cells group together to form tissues
Receptor: for recognition by hormones
Enzyme or signalling protein hydrophilic channel
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Receptor proteins Receptor: for recognition by hormones
These allow hormones / drugs to bind to cells and cause a response to happen inside the cell.
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Question: Label the diagram (11marks)1
2 10
3
4
5 6
8
9
11
Note: label the proteins based on location or structure, e.g. you do not need to identify receptors and enzymes.
1) carbohydrate; 2) glycoprotein; 3)integral protein; 4) peripheral protein; 5) carrier protein 6) hydrophilic channel; 7) phosphate group; 8) fatty acid; 9) phospholipid; 10) glycocalyx; 11) phospholipid bilayer click to cover answers
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Question: Explain why the model for membrane structure is known as the fluid mosaic model (3).
• The phospholipid molecules can move freely laterally and makes the membrane fluid.
• The proteins are distributed throughout the membrane un evenly and in a mosaic pattern.
• The agreed structure is based upon experimental and chemical evidence and so is classed as a model.
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Question: Describe the structure and function of the glycocalyx (a glycoprotein) (2)
• Consists of glycoproteins• Which are proteins with added carbohydrate chains• Used for cell recognition/receptors• Click here to hide answersClick to reveal answers
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Internal membranes
• The inner membranes of the mitochondria and chloroplasts contain enzymes and co enzymes. These allow respiration and phs to take place respectively.
• This is why the cristae and thylakoids exist.