Lipids

Question 1

2 groups of lipid

Answer 1

Triglycerides

Phospholipids

Question 2

Structure of a fatty acid

Answer 2

Variable R group - hydrocarbon chain (can be saturated or unsaturated)

-COOH = carboxyl group

Question 3

Describe the difference between saturated and unsaturated fatty acids

Answer 3

Saturated: no C=C double bonds in hydrocarbon chain; all carbons fully saturated with hydrogen

Unsaturated: one or more C=C double bond in hydrocarbon chain creating bend

Question 4

How do triglycerides form

Answer 4

1 glycerol molecule and 3 fatty acids

Condensation reaction

Removing 3 water molecules

Forming 3 ester bonds

Question 5

Function of triglycerides

Answer 5

Energy storage

Question 6

Explain how the properties of triglycerides are related to their structure

Answer 6

High ratio of C-H bonds to carbon atoms in hydrocarbon chain

So used in respiration to release more energy than same mass of carbohydrates

Hydrophobic fatty acids so insoluble in water

So no effect on water potential of cell

Question 7

Describe the difference between the structure of triglycerides and phospholipids

Answer 7

One of the fatty acids of a triglyceride is substituted by a phosphate-containing group

Question 8

Function of phospholipids

Answer 8

Form a bilayer in cell membrane

Allowing diffusion of lipid-soluble or very small
substances

And restricting movement of water-soluble or larger substances

Question 9

Describe how the properties of phospholipids relate to their structure

Answer 9

Phosphate heads are hydrophilic

Attracted to water so point to water

Fatty acid tails are hydrophobic

Repelled by water so point away from water

Question 10

Test for lipids

Answer 10

Add ethanol, shake to dissolve lipids, then add water

Positive = milky white emulsion