the structure of the plasma membrane
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The Structure of the Plasma Membrane. Membrane Structure. The plasma membrane is 8 nm thick. It is mainly made up of phospholipids and proteins. Membrane Structure. carbohydrate. cholesterol c. protein. Phospholipid bilayer. Membrane phospholipids. - PowerPoint PPT PresentationTRANSCRIPT
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The Structure of the Plasma Membrane
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Membrane Structure
• The plasma membrane is 8 nm thick.
• It is mainly made up of phospholipids and proteins.
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Membrane Structure
Phospholipid bilayer
protein
cholesterolc
carbohydrate
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Membrane phospholipids
• Phospholipids have a hydrophilic head and two hydrophobic tails.
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Membrane phospholipids
• The phospholipids form a bilayer- The hydrophilic heads face outward and the
hydrophobic tails face inward
Hydrophobictails
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Membrane Proteins
• Membrane proteins are found within the phospholipid bilayer
• They can extend all the way through the bilayer – integral proteins
• They can be found embedded on either surface – peripheral proteins
Integral Protein
Phospholipid bilayer
Peripheral protein
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Functions of Membrane Proteins
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• Some proteins transport substances across the membrane by forming channels or by physically moving them across the membrane.
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Membrane Proteins
Functions of membrane proteins include:• Transport of substances across the membrane• Join cells to one another• Act as enzymes• Bind to chemical messengers from other cells• Act as identification tags so cells can recognize one another• Attach to cytoskeleton and the extracellular matrix
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Membrane cholesterol and carbohydrates
Cholesterol• Cholesterol is found within the
phospholipid bilayer• It helps stabilize the
phospholipids
Carbohydrates• Located on outer layer of
membrane only• Bound to proteins (glycoproteins)
or phopholipids (glycolipids)• Act as identification tags for cell
cell recognition
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Fluid Mosaic Model
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Fluid Mosaic Model
• The membrane is a fluid mosaic• Fluid – the phospholipids and the proteins drift within the
membrane• Mosaic – the diversity of proteins found within the
membrane and the arrangement of these proteins in the membrane
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Lecture Review 11/281. What is the membrane mainly composed of?2. How are the phospholipids arranged in the
membrane?3. What are the 2 types of membrane proteins and
why are they different?4. What is the role of cholesterol?5. What is the role of carbohydrates?6. What are 2 functions of the proteins in the
membrane?7. Why is the current model called fluid mosaic?