1.3 Lipids

Question 1

What are the 2 groups of lipids?

Answer 1

1. Triglycerides
2. Phospholipids
   (Includes fats and oils)

Question 2

What elements do lipids contain?

Answer 2

Carbon, hydrogen, oxygen
however the proportion of oxygen is very small compared with carbohydrates

Question 3

Why are lipids not polymers?

Answer 3

They are not composed of repeating units (monomers)

Question 4

What is the structure of a triglyceride molecule?

Answer 4

• Has 1 molecule of glycerol joined by three covalent ester bonds formed in condensation reactions to 3 fatty acids.
  -3 molecules of water are removed
  There are over 70 fatty acids each with a COOH group with a hydrocarbon chain attached

Question 5

What are the functions of triglycerides?

Answer 5

1. Source of energy
2. Act as insulators
3. Waterproofing
4. Protection

Question 6

Why are triglycerides a good source of energy?

Answer 6

Lipids have a higher proportion of hydrogen to oxygen atoms and when oxidised release 2x the energy as the same mass as carbohydrates and proteins

Question 7

Why are triglycerides good insulators?

Answer 7

Thermal insulator - Fat is a slow conductor of heat and helps retain body heat
Electrical insulator - myelin sheath in nerve cells

Question 8

Why are triglycerides waterproofing?

Answer 8

They are large non polar molecules which are insoluble in water, therefore useful for waterproofing
E.g waxy cuticle in plants

Question 9

How do triglycerides provide good protection?

Answer 9

Fat is stored around delicate organs and acts as a shock absorber

Question 10

What are the 2 types of triglycerides?

Answer 10

1. Saturated - fatty acid has no C=C bond, all the carbon atoms are linked to the maximum number of hydrogen atoms
2. Unsaturated
   a) monounsaturated has one C=C bond
   b) polyunsaturated have more than one C=C bond

Question 11

What are the properties of saturated triglycerides

Answer 11

• high melting point
• solid at room temperature
  E.g butter

Question 12

What are the properties of unsaturated triglycerides

Answer 12

• low melting point
• liquid at room temperature
  E.g oil

Question 13

Where are phospholipids found?

Answer 13

Cell membranes

Question 14

What structure do phospholipids have?

Answer 14

• Contain a glycerol molecule, 2 fatty acids and a phosphate group

Question 15

Is the phosphate group in a phospholipid hydrophobic or hydrophilic?

Answer 15

Hydrophillic because the phosphate group is electrically charged (polar) making it attracted to water

Question 16

Is the hydrocarbon chain/tail of a phospholipid hydrophobic or hydrophilic?

Answer 16

Hydrophobic because the hydrocarbon tail is non-polar and therefore is repelled by water

Question 17

What happens when phospholipids are put in water?

Answer 17

They form a bilayer
- hydrophobic tails point towards the centre of the bilayer, the hydrophilic heads point outwards

Question 18

What is the function of the phospholipid bilayer?

Answer 18

Controls the movement of molecules through it.
The hydrophobic tails prevent water soluble molecules passing directly through the bilayer, however lipid soluble molecules can diffuse through directly

Question 19

Glucose is a ……….. substrate

Answer 19

Glucose is a respiratory substrate
(Used in respiration)