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biology year 1 > 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

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17
Q

Identify the molecule

A

Triglyceride

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18
Q

Identify the molecule

A

Saturated fatty acid

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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
33
Q

how do you test for lipids?

A

dissolve in alcohol, then

add water then

white emulsion shows presence of lipid

34
Q

name the bond between the glycerol and the fatty acid chains in a lipid molecule

A

ester

35
Q

How can you tell the difference between a fatty acid that is saturated and how which is not?

A

saturated FA have no double bonds between carbon atoms

36
Q

what is the difference between a triglyceride and a phospholipid?

A

in a phospholipid, one FA is replaced with a phosphate

37
Q

name the reaction to breakdown phospholipids to release the phosphate

A

hydrolysis

38
Q

name the element found in all amino acids but not in triglycerides?

A

Nitrogen

39
Q

what is the advantage of expressing omega-3 fatty acid concentration in cows as a percentage of total fat?

A

milk will vary between cows

40
Q

explain 2 ways in which fatty acids are important in the formation of new cells?

A

1- fatty acids used to make phospholipids

  • phospholipids in membranes
  • more phospholipids, more membranes made

2- fatty acids respire to release energy

  • more triglycerides
  • more energy released
  • energy used for cell production
41
Q

in a reaction, the concentration of lipase did not change during the course of the investigation.

explain why?

A

enzyme not used up in the reaction

42
Q

at a lower temperature how would you expect the curve to be plotted?

A

less steep

43
Q

compare and contrast the STRUCTURE and PROPERTIES of triglycerides and phospholipids?

A
  • both contain ester bonds
  • both contain glycerol
  • fatty acids on both can be unsaturated/saturated
  • both insoluble in water
  • triglyceride has 3 fatty acids whilst phospholipid has 2 and phosphate group
  • triglycerides are non-polar, phospholipids have polar and non polar regions
  • phospholipids form monolayer but triglycerides cant
44
Q

in an investigation, investigating the structure of surface membrane of cells,

explain why red blood cells were used in this investigation rather than white blood cells?

A
  • red blood cells have no nucleus
  • so cell surface memb easier to extract
45
Q

digestion of lipids

A
  1. bile neutralises stomach acid and emulsifies lipid to micelles, increasing surface area
  2. pancreas and intestinal glands secrete lipase which hydrolyses lipids to fatty acids and glycerol
  3. hydrolysis of ester bonds
  4. can be digested into mono and diglycerides
46
Q

absorption of products of lipid digestion

A

short chain fatty acids - diffuse straight into epithelial cells. Longer chain fatty acids and glycerol cannot so they undergo this process.

  1. packages with bile salts into micelles
  2. micelles then diffuse into epithelial cells
  3. micelles broken down and repackaged into triglycerides
  4. packages into lipid soluble chylomicrons in the golgi
  5. chylomicrons transported into the lacteal by exocytosis

biology year 1 (45 decks)

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