Lipids Flashcards

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1
Q

Describe the structure of a triglyceride molecule

A

1 Glycerol, 3 Fatty Acids

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2
Q

Describe the structure of a fatty acid.

A
  • Long ‘tails’ made of hydrocarbons that are hydrophobic.
  • These make lipids insoluble in water.
  • Fatty acids all have same basic structure, but hydrocarbon tail varies.
  • Carbon atom links fatty acid to glycerol.
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3
Q

How are triglycerides formed?

A

By condensation reactions.

  • A molecule of water is released as the ester bond is formed between fatty acid and glycerol.
  • This process happens twice more to form a triglyceride
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4
Q

What are the two kinds of fatty acids?

A

Saturated and Unsaturated

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5
Q

What is the structural difference between saturated and unsaturated fatty acids?

A

They have different hydrocarbon tails.
- Saturated fatty acids dont have any double bonds between their carbon atoms. The fatty acid is ‘saturated’ with hydrogen

  • Unsaturated fatty acids have at least one double bond between carbon atoms.
  • This causes the chain to kink.
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6
Q

What lipids are found in cell membranes?

A

Phospholipids.

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7
Q

Describe the structure of phospholipids.

A

1 Glycerol, 2 Fatty acids, 1 phosphate group.

- the phosphate group is hydrophilic (attracts water). The fatty acid tails are hydrophobic (repel water).

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8
Q

Why does the structure of triglycerides help them to be good energy storage molecules?

A
  • Lipids contain twice as much energy gram for gram as carbohydrates (hydrocarbon tails contain lots of energy)
  • Insoluble, so dont affect water potential. Triglycerides clump together as insoluble droplets bc fatty acid tails are hydrophobic, so tails face inwards protected by glycerol heads.
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9
Q

How do phospholipids form the bilayer of cell membranes?

A
  • Their heads are hydrophilic & tails are hydrophobic, so they form a double layer with their heads facing out towards the water on either side.
  • Centre of bilayer is hydrophobic so water-soluble substances cant easily pass though it-membrane acts as a barrier to these substances.
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10
Q

How to test for lipids?

A

Emulsion test.

  • shake substance with ethanol for a minute so it dissolves, then pour solution into water
  • any lipid will show up as a milky emulsion
  • more lipid there is, more noticeable milky colour will be.
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