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AQA B > 3.1.3 Lipids - Triglycerides, Phospholipids and the Emulsion Test > Flashcards

3.1.3 Lipids - Triglycerides, Phospholipids and the Emulsion Test Flashcards

1
Q

Which 3 elements do lipids contain?

A

Carbon

Hydrogen

Oxygen

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2
Q

Which part of a phospholipid is hydrophilic?

A

The phosphate ‘head’

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3
Q

Identify the molecule

A

Polyunsaturated fatty acid

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4
Q

What does hydrophobic mean?

A

water hating

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5
Q

How does the structure of triglycerides relate to their properties?

A
  • High ratio of carbon-hydrogen bonds make them an excellent energy source
  • Low mass to energy ratio- animals don’t have to carry a heavy energy store around.
  • Non-polar molecules are insoluble in water so they do not affect osmosis in cells.
  • High ratio of hydrogen to oxygen atoms so water released when trigylcerides are oxidised. Good for animals in deserts.
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6
Q

Identify the molecule

A

Monounsaturated fatty acid

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7
Q

Identify the molecule

A

Phosphate molecule

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8
Q

What state do monounsaturated and polyunsaturated fats take at room temperature?

A

Liquid - they are oils.

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9
Q

What is mean by a saturated fatty acid?

A

A fatty acid that contains no double bonds between the carbon atoms

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10
Q

Identify the molecule

A

Glycerol

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11
Q

Phospholipids are p___________ molecules

A

polar

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12
Q

What does the following describe:

  • Add 2cm3 of food and add to a test tube.
  • Add 5 cm3 of ethanol
  • Shake the tube thoroughly to dissolve any lipid.
  • Add 5cm3 of water and shake gently
  • A cloudy-white colour indicates a positive result.
A

The emulsion test for lipids

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13
Q

What state do saturated lipids take at room temperature?

A

Solid - they are fats

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14
Q

What is meant by a polyunsaturated fatty acid?

A

A fatty acid that contains more than 1 double bond between its carbon atoms.

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15
Q

What does hydrophilic mean?

A

attracted to water

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16
Q

What type of bond forms between glycerol and fatty acid molecules?

A

Ester bond

17
Q

Identify the molecule

A

Triglyceride

18
Q

Identify the molecule

A

Saturated fatty acid

19
Q

What type of reaction takes place when a fatty acid molecule is removed from a glycerol molecule?

A

Hydrolysis

20
Q

What type of reaction takes place when a glycerol molecule joins with a fatty acid molecule?

A

Condensation reaction

21
Q

Describe how you would carry out an emulsion test for lipids

A

The emulsion test for lipids:

  • Add 2cm3 of food and add to a test tube.
  • Add 5 cm3 of ethanol
  • Shake the tube thoroughly to dissolve any lipid.
  • Add 5cm3 of water and shake gently
  • A cloudy-white colour indicates a positive result.
22
Q

Which part of a phospholipid is hydrophobic?

A

The fatty acid ‘tails’

23
Q

What decides the properties of different fats and oils?

A

Variations in their fatty acid chains

24
Q

List the roles of lipids in living organisms.

A
  • Cell membranes
  • Energy store
  • Waterproofing
  • Heat insulation
  • Electrical insulation
  • Protection of organs e.g. kidneys
25
Q

Why are triglycerides called triglycerides?

A

They contain 1 glycerol molecule (glyceride) and 3 fatty acids (tri)

26
Q

What is meant by a monounsaturated fatty acid?

A

A fatty acid that contains 1 double bond between 1 pair of its carbon atoms.

27
Q

Describe the structure of a phospholipid

A

1 glycerol molecule attached to

2 fatty acid molecules and

1 phosphate molecule

28
Q

How does the structure of phospholipids relate to their properties?

A
  • Polar molecules - meaning that they can form a barrier (cell membrane) between water inside and outside a cell.
  • The phospholipid can form glycolipids by combining with carbohydrates. These are important in cell recognition.
29
Q

Name the 2 main groups of lipid

A

Triglycerides (fats and oils)

Phospholipids

30
Q

What happens when a phospholipid is placed in water?

A

The hydrophilic head positions itself towards water.

The hydrophobic tail positions itself away from water

31
Q

Identify the molecule

A

Phospholipid

32
Q

List the characteristics shared by all lipids

A
  • They contain: Carbon, Hydrogen and Oxygen
  • Lower proportion of oxygen to carbon and hydrogen than carbohydrates.
  • Insoluble in water
  • Soluble in organic solvents e.g. alcohols

AQA B (31 decks)

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