3.5 Lipids

Question 1

What is a lipid?

Answer 1

Non-polar macromolecules

containing elements carbon hydrogen & oxygen.

Commonly known as fats & oils.

Question 2

What is the difference between fats & oils?

Answer 2

Both are types of lipids:

fats are solid at room temperature

oils are liquid at room temperature

Question 3

What is a triglyceride?

Answer 3

Lipid

composed of glycerol + 3 fatty acids

Question 4

What is a triglyceride?

Answer 4

Lipid

composed of glycerol + 3 fatty acids

Question 5

What is the name of the bond which holds together fatty acids & glycerol in triglycerides?

Answer 5

ester bond

Question 6

Describe the structure of a triglyceride:

Answer 6

Glycerol molecule

bonded to 3 fatty acids

by ester bonds

Question 7

What is the difference between saturated & unsaturated triglycerides?

Answer 7

Saturated = no double bonds in fatty acid chains.

Unsaturated = at least 1 double bond in fatty acid chains.

Question 8

Explain the difference in physical properties of saturated & unsaturated triglycerides:

Answer 8

Saturated fatty acids have no C = C double bonds

fatty acid chains are regular, can pack closer together

higher melting point, ∴ solid at room temperature

Question 9

Plants contain [saturated/unsaturated] triglycerides.

Answer 9

unsaturated

Question 10

Along with carbon, hydrogen & oxygen, phospholipids also contain the element ____.

Answer 10

phosphorus

(makes up phosphate group)

Question 11

Why are phospholipids called surfactants?

Answer 11

Form layer on surface of water

with phosphate heads facing down & fatty acid tails up

Question 12

What is a sterol?

Answer 12

Type of amphipathic lipid/alcohol

Question 13

What is a sterol?

Answer 13

Type of amphipathic lipid/alcohol

based on four carbon ring structure + OH

Question 14

What is cholesterol used to manufacture in the body?

Answer 14

Vitamin D

Steroid hormones

Bile

Question 15

What are the roles of lipids?

Answer 15

• MEMBRANE & HYDROPHOBIC BARRIER formation
• HORMONE production
• ELECTRICAL INSULATION for impulse transmission
• WATERPROOFING

Question 15

What are the roles of lipids?

Answer 15

• MEMBRANE & HYDROPHOBIC BARRIER formation
• HORMONE production
• ELECTRICAL INSULATION for impulse transmission
• WATERPROOFING

Also stored under skin & around vital organs for:

• THERMAL INSULATION
• CUSHIONING organs
• BUOYANCY in aquatic animals

Question 16

What is the test for lipids?

Answer 16

emulsion test

Question 17

How do you carry out a test for lipids?

Answer 17

1. Mix sample with ethanol (dissolves lipid)
2. Add water (water is more soluble than lipids in ethanol, so displaces lipids from solution)
3. Shake
4. Positive result = while emulsion layer on top of solution (lipids have been displaced from their solution, forming precipitate)
5. Negative result = solution remains clear