Biological Molecules: Lipids

Question 1

What are the two groups of lipids?

Answer 1

triglycerides and phospholipids

Question 2

what are triglycerides?

Answer 2

formed from the condensation reaction of 1 molecule of glycerol and 3 molecules of fatty acids

Question 3

what bond is formed by the condensation reaction between a glycerol and fatty acid?

Answer 3

ester bond

Question 4

what can the R group of a fatty acid be?

Answer 4

saturated or unsaturated

Question 5

what are saturated fatty acids?

Answer 5

single bonds between carbon atoms

Question 6

what are unsaturated fatty acids?

Answer 6

double bond between carbon atoms

Question 7

what are phospholipids?

Answer 7

formed by the condensation reaction of 1 molecule of glycerol, 2 molecules of fatty acids and 1 molecules of a phosphate- containing group

Question 8

what is a fatty acid(formula)?

Answer 8

RCOOH

Question 9

what are properties of triglycerides?

Answer 9

• energy storage molecules
• insoluble in water, don’t affect the water potential of the cell and cause water to enter cell by osmosis(swell)

Question 10

what are properties of phospholipids?

Answer 10

• make up the bilayer of cell membranes
• hydrophilic heads
• hydrophobic tails: centre of bilayer is hydrophobic so water soluble molecules cannot easily pass through

Question 11

how do we test for lipids?

Answer 11

• emulsion test
• add ethanol
• shake
• add water
• milky white emulsion forms to show the presence of a lipid

Question 12

what is the difference between the structure of a triglyceride and a phospholipid molecule?

Answer 12

in a phospholipid, one fatty acid is replaced by a phosphate