3.1.3lipids and phospholipids

Question 1

What are fatty acids?

Answer 1

Long non-polar hydrocarbon chains containing a COOH (carboxylic group) at one end.

Question 2

What are the roles of lipids

Answer 2

• Source of energy: twice as much as carbohydrates for same mass
• Waterproofing: insoluble in water
• Insulation: slow heat conductors so help retain heat
• Protection: fat stored around delicate organs
• Phospholipids make up cell membranes

Question 3

How are triglycerides formed?

Answer 3

Condensation reactions between 1 glycerol and 3 fatty acids to produce 3 molecules of water.
Forms ester bond.

Question 4

Describe the structure and formation of triglycerides

Answer 4

3 fatty acids combined with one glycerol molecule
Glycerol is a fatty acid containing 3 hydroxyl groups which react with 3 fatty acids to form ester bonds

Question 5

Are phospholipids hydrophilic or hydrophobic?

Answer 5

Hydrophilic head, hydrophobic tail

Question 6

What are saturated fatty acids?

Answer 6

• Fatty acids with no double bonds between 2 carbon atoms
• saturated with hydrogen

Question 7

What are phospholipids?

Answer 7

2 fatty acids, one glycerol and one phosphate molecule. (Like triglycerides but one fatty acid replaced by phosphate molecule)

Question 8

Are lipids soluble?

Answer 8

Soluble in organic solvents (e.g. alcohol)
Insoluble in water

Question 9

Are triglycerides hydrophilic or hydrophobic?

Answer 9

Hydrophobic

Question 10

What are the differences between triglycerides and phospholipids?

Answer 10

• Triglycerides have 3 fatty acids but phospholipids have 2 fatty acids and a phosphate group
• Triglycerides are hydrophobic but phospholipids have hydrophobic and hydrophilic regions
• Phospholipids form bilayer in water but Triglycerides don’t

Question 11

What are the similarities between triglycerides and phospholipids?

Answer 11

• Contain ester bonds
• Contain glycerol
• Fatty acids may be saturated or unsaturated
• Insoluble in water
• Contain C, O and H

Question 12

What are unsaturated fatty acids?

Answer 12

Mono-unsaturated fatty acids: one carbon to carbon double bond
Poly-unsaturated fatty acids: 2+ carbon to carbon double bonds

Double bonds cause the chain to bend

Question 13

What is the general structure of a fatty acid?

Answer 13

R.COOH
R group is a long hydrocarbon chain

Question 14

Compare the structure of starch and cellulose MOVE

Answer 14

• Both polysaccharides/polymers of glucose
• Both glycosidic bonds
• Both contain O H C
• Starch helical/coiled, cellulose straight
• starch branched, cellulose unbranched
• starch no microfibrils, cellulose microfibrils
• starch 2 types of molecule (amylose and amylopectin)
• starch 1-6 glycosidic bonds, cellulose 1-4