(3.1.3) lipids

Question 1

what are lipids?

Answer 1

molecules made from carbon, hydrogen and oxygen which are only soluble in organic solvents.

Question 2

what are fatty acids?

Answer 2

fatty acids are long chains of hydrocarbons with a carboxyl group (-COOH) at one end

Question 3

describe the difference between a saturated and an unsaturated fatty acid

Answer 3

• saturated fatty acids only have single C-C bonds
• unsaturated fatty acids have one or more double C=C bonds

Question 4

what is the formation of triglycerides?

Answer 4

• are made from one glycerol molecule and three fatty acid molecules.
• a condensation reaction chemically links together with the elimination of three water molecules.
• ester bonds formed between hydroxyl groups.

Question 5

what are properties of triglycerides?

Answer 5

• high number of carbon-hydrogen bonds meaning they’re an excellent energy store
• low mass to energy ratio meaning they’re a good storage molecule
• large + non-polar (insoluble) meaning their storage doesn’t affect the cell water potential

Question 6

what is the formation of phospholipids?

Answer 6

• are made from one glycerol molecule, two fatty acid molecules and one molecule of phosphate
• one fatty acid molecule is replaced by the phosphate molecule
• condensation reactions, eliminating three molecules of water and forming ester bonds
• non-polar, hydrophobic fatty acid tails + polar, hydrophilic phosphate head

Question 7

what are properties of phospholipids?

Answer 7

• in an aqueous environment being polar means a bilayer can be formed
• hydrophilic heads can be used to hold at the surface of cell membrane
• structure allows them to form glycolipids w/ carbohydrates, important for cell recognition

Question 8

how do you test for lipids?

Answer 8

1. mix test sample with ethanol in test tube and shake thoroughly
2. add water and shake gently

a cloudy-white emulsion appears if the result is postive