Lipids

Question 1

What are the 2 groups of lipids?

Answer 1

triglyceride & phospholipids

Question 2

What is the structure of a fatty acid?

Answer 2

• R-group attached to hydrocarbon chain (saturated or unsaturated)
• carboxyl group (COOH)

Question 3

What is the difference between saturated & unsaturated fatty acids?

Answer 3

saturated has no double carbon-carbon bond whilst unsaturated has one more double bond in the hydrocarbon chain which creates a kink

Question 4

How do triglycerides form?

Answer 4

one glycerol molecule joined to 3 fatty acids forming 3 ester bonds by a condensation reaction which forms 3 molecules of water

Question 5

How are the properties of triglycerides related to its structure?

Answer 5

function: energy storage
- high ratio of C-H bonds to C atoms - used in respiration to release more energy than same mass of carbohydrates
- hydrophobic/non-polar - clumps together as droplets which don’t affect water potential & can be used for water proofing

Question 6

What is the structural difference between triglycerides & phospholipids?

Answer 6

phospholipids have a phosphate -containing group instead of one of the fatty acid tails

Question 7

How are the properties if phospholipids related to its structure?

Answer 7

function: form a bilayer in plasma membrane allowing diffusion of lipid-soluble & restricting movement of water-soluble molecules
- phosphate heads are hydrophilic so attracted to water
- fatty acid tails are hydrophobic so are repelled by water

Question 8

What is the test for lipids?

Answer 8

1. Add ethanol, shake & then add water
2. Milky white emulsion produced from positive test