Biological Molecules - 3.1.3 Lipids - Triglycerides, Phospholipids and the Emulsion Test Flashcards Preview

As-Level Biology > Biological Molecules - 3.1.3 Lipids - Triglycerides, Phospholipids and the Emulsion Test > Flashcards

Flashcards in Biological Molecules - 3.1.3 Lipids - Triglycerides, Phospholipids and the Emulsion Test Deck (33)
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1

Which 3 elements do lipids contain?

Carbon

Hydrogen

Oxygen

2

Which part of a phospholipid is hydrophilic?

The phosphate 'head'

3

What does hydrophobic mean?

water hating

4

How does the structure of triglycerides relate to their properties?

  • 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.

5

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

Liquid - they are oils.

6

What is mean by a saturated fatty acid?

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

7

Phospholipids are p___________ molecules

polar

8

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.

The emulsion test for lipids

9

What state do saturated lipids take at room temperature?

Solid - they are fats

10

What is meant by a polyunsaturated fatty acid?

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

11

What does hydrophilic mean?

attracted to water

12

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

Ester bond

13

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

Hydrolysis

14

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

Condensation reaction

15

Describe how you would carry out an emulsion test for lipids

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.

16

Which part of a phospholipid is hydrophobic?

The fatty acid 'tails'

17

What decides the properties of different fats and oils?

Variations in their fatty acid chains

18

List the roles of lipids in living organisms.

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

19

Why are triglycerides called triglycerides?

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

20

What is meant by a monounsaturated fatty acid?

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

21

Describe the structure of a phospholipid

1 glycerol molecule attached to

2 fatty acid molecules and

1 phosphate molecule

22

How does the structure of phospholipids relate to their properties?

  • 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.

23

Name the 2 main groups of lipid

Triglycerides (fats and oils)

Phospholipids

24

What happens when a phospholipid is placed in water?

The hydrophilic head positions itself towards water.

The hydrophobic tail positions itself away from water

25

List the characteristics shared by all lipids

  • 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

26

how do you test for lipids?

dissolve in alcohol, then

add water then

white emulsion shows presence of lipid

27

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

ester

28

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

saturated FA have no double bonds between carbon atoms

29

what is the difference between a triglyceride and a phospholipid?

in a phospholipid, one FA is replaced with a phosphate

30

name the reaction to breakdown phospholipids to release the phosphate

hydrolysis

31

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

Nitrogen

32

Compare and contrast structure of triglycerides and phospholipids

Both have ester bond

both contain glycerol

fatty acids on both can be saturated or unsaturated

Both contain C, H, O but phospholipids have also P

Triglycerides have 3 FA, Phospholipds have 2 FA and 1 phosphate group

33

Compare and contrast the properties of triglycerides and phospholipids

Both insoluble in water

Triglycerides are hydrophobic/non polar but phospholipids have hydrophobic and hydrophillic (polar) regions

Phospholipids form a micelle bilayer but triglycerides dont

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