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Biological Molecules Topic One AQA A-Level > Lipids > Flashcards

Lipids Flashcards

1
Q

What are the most common lipids?

A

Triglycerides and phospholipids

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2
Q

Are lipids hydrophobic or hydrophilic?

A

Hydrophobic

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3
Q

What are triglycerides used for?

A

Insulation, storage, and protection of organs

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4
Q

Why are triglycerides good for energy storage?

A

When oxidized, they yield more energy per unit mass than carbohydrates

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5
Q

Why are triglycerides not good for quick energy?

A

They can’t be mobilised quickly because they are very insoluble.

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6
Q

What are triglycerides made from?

A

One glycerol molecule and three fatty acid molecules

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7
Q

What is the R group of fatty acids?

A

COOH

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8
Q

What is the structure of fatty acids?

A
  • made of non-polar hydrocarbon chains with a polar carboxyl acid group at one end.
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9
Q

How are triglycerides formed?

A
  • 3 Fatty acid molecules
  • 1 glycerol molecule
  • 3 condensation reactions to form 3 ester bonds
  • 3 water molecules also produced
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10
Q

Structure of an ester bond

A

O=C

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11
Q

Whats the difference between saturated and unsaturated fatty acids?

A

Unsaturated fatty acids have C=C double bonds, whereas saturated fatty acids have no C=C double bonds

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12
Q

What are some features of triglycerides with saturated fatty acids?

A
  • High melting points
  • Found in warm blooded animals
  • Solid at room temperature
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13
Q

What are some features of triglycerides with unsaturated fatty acids?

A
  • Low melting points
  • Found in cold blooded animals
  • Liquid at room temperature
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14
Q

What is the difference between monounsaturated and polyunsaturated fatty acids.

A

Polyunsaturated fatty acids have more than one C=C bond, monounsaturated acids only have one C=C bond.

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15
Q

What makes a phosphodiester bond different to a triglyceride?

A

They have a phosphate group

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16
Q

What is the structure of a phospholipid?

A
  • Polar hydrophilic ‘head’ (the negatively charged phosphate group)
  • Two non-polar hydrophobic ‘tails’ (fatty acid chains)
17
Q

Which type of bond joins the glycerol molecule to the phosphate group?

A

Phosphoester bond

18
Q

What happens when phospholipids are mixed with water?

A
  • FORM A LIPOSOME
  • Double-layered phospholipid bilayer (the hydrophilic heads face the water and the hydrophobic tails face eachother
19
Q

What is the biochemical test for lipids?

A

The alcohol emulsion test

20
Q

What is the method for the alcohol emulsion test?

A
  • Shake the sample with ethanol
  • Decant the liquid into water
  • A positive test will result in a cloudy emulsion forming because the lipids dissolved in ethanol will form a precipitate.

Biological Molecules Topic One AQA A-Level (7 decks)

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