1 Biological Molecules: Lipids

Question 1

What is a glycerol?

Answer 1

• a molecule which combines with 3 fatty acids to form triglycerides
• 3 carbon chain with 3 hydroxyl groups

Question 2

What does hydrophilic mean?

Answer 2

• section of a molecule attracted to water

Question 3

What does hydrophobic mean?

Answer 3

• section of a molecule repelled by water

Question 4

What is a lipid?

Answer 4

• class or organic compounds
• fatty acids are their product
• insoluble in water
• soluble in organic solvents e.g triglycerides, phospholipids, waxes, steroids

Question 5

What is a mono- unsaturated fatty acid?

Answer 5

• fatty acid which posses a carbon chain with a single double bond between carbon atoms

Question 6

What is a phospholipid?

Answer 6

• triglyceride in which one of the three fatty acids are replaced by a phosphate molecule
• important in the structure and functioning of plasma membranes

Question 7

What is a poly- unsaturated fatty acid?

Answer 7

• fatty acid which posses a carbon chain with many double bonds between carbon atoms

Question 8

What is a saturated fatty acid?

Answer 8

• a fatty acid in which there are not any double bonds with carbon atoms

Question 9

What is a triglyceride?

Answer 9

• individual lipid molecule made up of a glycerol molecule and 3 fatty acids
• contains ester bonds

Question 10

What is the emulsion test?

Answer 10

• the test for lipids

Question 11

What are lipids used for?

Answer 11

• provide an energy source
• help to insulate organisms
• act as waterproofing from membranes
• hormones

Question 12

Components of a triglyceride:

Answer 12

• glycerol molecule
• 3 fatty acids

Question 13

Components of a phospholipid:

Answer 13

• glycerol molecule
• 2 fatty acids
• phosphate group

Question 14

Bond name in triglycerides and how they are formed:

Answer 14

• ester bonds
• condensation reaction between each of the three OH groups on the glycerol and the OH group of each fatty acid chain

Question 15

Bond name in phospholipids and how they are formed:

Answer 15

• ester bonds
• formed by condensation reaction of the 2 OH groups on the glycerol and the OH groups of each fatty acid chains

Question 16

What are the triglycerides properties?

Answer 16

• fatty acids chains are hydrophobic which makes lipids insoluble in water
• bundle as insoluble droplets since tails face inwards , glycerol heads shield them from water
• hydrocarbon fatty acid chains can be saturated or unsaturated

Question 17

What are the phospholipids properties?

Answer 17

• phosphate group is hydrophilic and the fatty acid chains are hydrophobic which allows phospholipid to from bilayer which make up membranes in and around cells

Question 18

What are triglycerides used for?

Answer 18

• used as energy store as there is a lot of energy released when fatty acid chains are broken down

Question 19

What are phospholipids used for?

Answer 19

• membranes
• hormones e.g testosterone

Question 20

What happens when phospholipids are placed in water and why ?

Answer 20

• phospholipid heads are hydrophilic , phospholipid tails are hydrophobic
• when placed in water, double layer is formed
• heads facing outwards, tails facing inwards
• centre of bilayer is hydrophobic so water soluble substances cannot easily pass through
• this creates a barrier and allows separation of solutions and can create different conditions either side of the membrane
• don’t mix in water/ insoluble in water

Question 21

What is the method of the Emulsion test?

Answer 21

• add ice cold ethanol to the sample = dissolve lipids
• add water to the sample and shake vigorously for a minute = dissolve lipids
  -if lipids are present = a milky white emulsion will form will form as a top layer

Question 22

Qualitative measurements of the Emulsion Test:

Answer 22

• if more lipids are present, the more milky/ opaque the precipitate will be

Question 23

What are most lipids?

Answer 23

• triglycerides

Question 24

Why aren’t lipids used more for energy?

Answer 24

• lipids store more energy
• glucose is most used in the body as it is easier to hydrolyse

Question 25

Is the phospholipid polar or non polar and why?

Answer 25

- polar - because its phosphate group is polar - polar = has a charge

Question 26

Are cis fats good or bad?

Answer 26

- good

Question 27

Why are cis fats bad?

Answer 27

- unsaturated = has double bonds - raises good cholesterol levels

Question 28

Are trans fats good or bad?

Answer 28

- bad

Question 29

Why are trans fats bad?

Answer 29

- saturated = no double bonds - raises bad cholesterol levels

Question 30

In cis fats , where are the hydrogens located?

Answer 30

- hydrogens on same side of the hydrocarbon

Question 31

In trans fats, where are the hydrogens located?

Answer 31

- hydrogens on the opposite side of the hydrocarbon