LIPIDS

Question 1

Elements in lipids

Answer 1

• Carbon
• Hydrogen
• Oxygen

Question 2

Compare elements in lipids to elements in carbohydrates

Answer 2

Lipids have a lower proportion of oxygen and higher proportion of hydrogen compared to carbohydrates

Question 3

2 types of lipids?

Answer 3

• Triglycerides
• Phospholipids

Question 4

Properties of lipids

Answer 4

• Insoluble in water
• Solid or liquid at room temperature
• Soluble in organic solvents like alcohol

Question 5

Roles of lipids

Answer 5

1) Energy store: lipids provide twice and much as energy as carbohydrates
2) Waterproofing: Lipids are insoluble in water.
3) Good insulators: fats are slow conductors of heat
4) Protection: fat is stored around the organs
5) PLASMA MEMBRANE: MADE UP OF PHOSPHOLIPIDS

Question 6

Structure of triglycerides

Answer 6

• 3 Fatty acids joined to 1 glycerol molecule
• Joined by a condensation reaction
• Forms an ester bond
• 3 fatty acids + 1 glycerol = R-COOH

Question 7

2 types of fatty acids

Answer 7

• Saturated : no double bonds between carbon
• Unsaturated : one or more double bonds between carbon

Question 8

Hydrolysis of lipids

Answer 8

• heat with acid
• Use enzyme lipase at its optimum temperature

Question 9

Similarities between carbohydrates and lipids

Answer 9

• Both can be hydrolysed
• Both made up of carbon, hydrogen and oxygen
• Both made through a condensation reaction
• Both sources of energy

Question 10

Differences between carbohydrates and lipids

Answer 10

• Lipids have a low proportion of oxygen whereas carbohydrates have higher
• Lipids are insoluble whereas carbohydrates are soluble
• Carbohydrates are polymers whereas lipids aren’t
• Carbohydrates have glycosidic bonds whereas lipids have ester bonds

Question 11

Structure of a phospholipid

Answer 11

• Contains 1 glycerol, 2 fatty acids and a phosphate
• Joined in a condensation reaction
• to form ester bonds

Question 12

What does a phospholipid molecule consist of

Answer 12

• Polar hydrophyllic head (attracts water)
• Non-polar hydrophobic tails (repels water)

Question 13

Why do phospholipids form a bilayer

Answer 13

Phospholipids form a bilayer due to hydrophobic tails being repelled by water.

Question 14

Differences between trigylcerides and phospholipids

Answer 14

• Trigylcerides have 3 fatty acids and phospholipids have 2 fatty acids + phosphate group
• Triglycerides are hydrophobic whereas phospholipids have hydrophobic and hydrophillic region

Question 15

Similarities between triglycerides and phospholipids

Answer 15

• a small amount of the sample placed in test tube with ethanol
• shake so fat dissolves
• add water
• white emulsion = lipids