Lipids - Phospholipids and Cholesterol.

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  • Created by: shyde7
  • Created on: 28-03-16 13:05
What is different about the structure of phospholipids and the structure of triglycerides?
One of the fatty acids is replaced by a phosphate group.
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How is the phosphate group bonded to the molecule?
A consensation reaction between an -OH group on a phosphoric acid molecule (H3PO4) and one of the three free -OH groups. This forms an ester bond.
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What is special about the carbon atoms of fatty acids in phospholipids?
They are an even number - usually 16 or 18.
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What is special about the fatty acids themselves in a phospholipid?
Commonly one of the chains are saturated and the other is unsaturated.
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What does hydrophilic mean?
Attracted to water.
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What does hydrophobic mean?
Repelled by water.
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Which part of the phospholipid molecule is hydrophilic?
The phosphate group, as it has a negative charge and so is polar.
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Which part of the phospholipid molecule is hydrophobic?
The fatty acid tails, as they are non-polar.
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Given that the head is hydrophilic and the tail is hydrophobic, what name is given to the phospholipid molecule?
Amphipathic.
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Which lipids are more likely to be amphipathic?
Membrane lipids, whereas storage lipids are not.
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When in water, what structures do phospholipids assume?
They may form a layer on the surface with the heads in the water and the tails sticking out or may form micelles - spheres with the heads on the outside and the tails inside.
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How much of membranes within cells of plants and animals are phospholipids?
Between 20% and 80%.
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What is different about bacterial membranes?
They tend to contain a greater proportion of protein.
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What gives the phospholipid membrane stability?
The fact that phospholipids can move in their layer, but not into a position where the tails are exposed to water.
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Which are the only molecules that can move through the phospholipid tails in the bilayer?
Small and non-polar ones e.g. oxygen and carbon dioxide.
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What is a steroid alcohol (sterol)?
A type of lipid which is not made from glycerol or fatty acids.
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True or false: cholesterol is a sterol?
True.
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What does cholesterol consist of?
Four carbon-based rings (or isoprene units).
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Is cholesterol hydrophobic or hydrophilic?
Hydrophobic.
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Why is being hydropphobic a good thing for cholesterol?
It can sit in the middle of the hydrophobic part of the bilayer and regulate fluidity. This prevents the membrane from becoming too fluid or stiff.
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Where is cholesterol made in mammals?
In the liver (mainly).
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What is the cholesterol derivative that plants use?
Stigmasterol. It differs in only one respect - it has a double bond between carbons 22 and 23.
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Which hormones are made from cholesterol?
Steroid hormones e.g. testosterone, oestrogen etc.
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What is the other class of lipids that plants possess?
Terpenes. They are constructed fro isoprene units like steroids.
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Other cards in this set

Card 2

Front

How is the phosphate group bonded to the molecule?

Back

A consensation reaction between an -OH group on a phosphoric acid molecule (H3PO4) and one of the three free -OH groups. This forms an ester bond.

Card 3

Front

What is special about the carbon atoms of fatty acids in phospholipids?

Back

Preview of the front of card 3

Card 4

Front

What is special about the fatty acids themselves in a phospholipid?

Back

Preview of the front of card 4

Card 5

Front

What does hydrophilic mean?

Back

Preview of the front of card 5
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