3.1.3 │ LIPIDS

Question 1

name the two groups of lipids

Answer 1

phospholipid and triglycerides

Question 2

how are triglycerides formed

Answer 2

condensation of one molecule of glycerol and three molecules of fatty acid releasing three water molecules and forming three ester bonds

Question 3

describe the structure of a fatty acid (RCOOH)

Answer 3

Variable R-group - hydrocarbon chain (saturated or unsaturated)-COOH = carboxyl group

Question 4

describe the difference between saturated and unsaturated fatty acids

Answer 4

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 5

what is the function of a triglyceride

Answer 5

energy storage

Question 6

describe the difference between the structure of phospholipids and triglycerides

Answer 6

in phospholipid, one fatty acid replaced by a phosphate

Question 7

explain how the properties of triglycerides are related to their structure

Answer 7

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 / non-polar fatty acids so insoluble in water (clump together as droplets)
so no effect on water potential of cell (or can be used for waterproofing)

Question 8

describe the structure of a phospholipid

Answer 8

phosphate group, glycerol molecule and two fatty acids bonded together by ester bonds

Question 9

describe the structure of a triglyceride

Answer 9

one glycerol molecules bonded to three fatty acids by ester bonds

Question 10

what is the function of a phospholipid

Answer 10

forms a bilayer in cell membrane, allowing diffusion of lipid-soluble (non-polar) or very small
substances and restricting movement of water-soluble (polar) or larger substances

Question 11

describe how the properties of phospholipids relate to their structure

Answer 11

phosphate heads are hydrophilic - attracted to water so point to water (aqueous environment) either side of membrane
fatty acid tails are hydrophobic - repelled by water so point away from water / to interior of membrane

Question 12

describe the test for lipids

Answer 12

add ethanol to sample, shake then add water
positive = milky white emulsion