Cell membranes and transport

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  • Created by: zoolouise
  • Created on: 20-04-16 12:04
What is the cell membrane and what does it control?
It's a boundary that separates the living cell from it's non-living surroundings. It controls which substances can enter/leave the cell.
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Who was the structure of the membrane described by and what as?
Described by Singer and Nicholson as a fluid mosaic. Fluid as the individual phospholipids can move about within the layer. Mosaic because the proteins appear dotted throughout the layer like a mosaic.
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What is the cell membrane almost entirely made up of?
Phospholipids and proteins.
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How are phospholipids made and what are they?
By replacing one of the fatty acids of a triglyceride with a phosphate group. It's a polar molecule, phosphate head is hydrophillipic and liphobic and fatty acid tails are hydrophobic and lipophillic. They can create a bilayer.
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What does Singer and Nicholsons model for the structure of the cell/plasma membrane state?
There's a bimolecular phospholipid layer, variety of proteins associated w/bilayer. Some proteins occur on just one layer of membrane and are extrinsic, some span both layers and are intrinsic proteins.
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What do phospholids create and what are their tails?
They create the bilayer and act as a barrier to most water-soluble substances. Their tales are non-polar so it's difficult for molecules/ions to pass through them.
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What do phospholipids allow?
They allow lipid-soluble materials to move through the membrane easily. Small, uncharged molecules can also pass through the bilayer easily.
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What are some facts about the phospholipid tails?
The fatty acid tails can be saturated or unsaturated. More unsaturated tails, more fluid the membrane is. Tails face inward creating a hydrophobic interior to the bilayer.
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What does cholesterol do?
Occurs throughout membranes of animal cells. Adds strength to cell membranes, a necessary feature in the absence of a cell water. They're very hydrophobic, prevent leakage of water/dissolved ions out of the cell. Regulate fluidity.
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What are extrinsic proteins?
Occur on the surface of the bilayer/partly embedded into it. Act to give mechanical support to the membrane. Some have carbohydrate chains added to them making glycoproteins - having a role in cell recognition and cell interaction.
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What are intrinsic proteins?
These completely span the bilayer, some act as carriers to transport water-soluble materials across the bilayer. Some are enzymes.
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What are channel proteins?
They consist of a pore lined with polar groups allowing charged ions to pass through as well as water soluble substances. Each channel protein is specific for one type of ion, they can open/close depending on cell needs.
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What are carrier proteins?
They allow the diffusion across the membrane of large, polar molecules such as sugars and amino acids. A particular molecule attaches to the carrier protein at its binding site, causes carrier protein to change shape.
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Card 2

Front

Who was the structure of the membrane described by and what as?

Back

Described by Singer and Nicholson as a fluid mosaic. Fluid as the individual phospholipids can move about within the layer. Mosaic because the proteins appear dotted throughout the layer like a mosaic.

Card 3

Front

What is the cell membrane almost entirely made up of?

Back

Preview of the front of card 3

Card 4

Front

How are phospholipids made and what are they?

Back

Preview of the front of card 4

Card 5

Front

What does Singer and Nicholsons model for the structure of the cell/plasma membrane state?

Back

Preview of the front of card 5
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