1.3 - Lipids

Question 1

What are the two groups of lipids?

Answer 1

• Triglycerides
• Phospholipids

Question 2

In what reaction are triglycerides formed?

Answer 2

Formed by the condensation reaction of one molecule of glycerol and three molecules of fatty acid.

Question 3

What bond is formed in the reaction between glycerol and fatty acid?

Answer 3

An ester bond

Question 4

What is the emulsion test for lipids?

Answer 4

1) Shake the test substance with ethanol for about a minute so that it dissolves, then pour the solution into water.
2) Any lipid will show up us a milky emulsion.
3) The more liquid there is, the more noticeable the milky colour will be.

Question 5

What is the main use of triglycerides?

Answer 5

Mainly used as energy storage molecules

Question 6

What are some properties of triglycerides and how do they releate to their structure?

Answer 6

• Long hydrocarbon tails of fatty acids contain lots of chemical energy (release lots when broken down)
• Insoluble, so don’t affect water potential
• Clump together as insoluble droplets in cells due to hydrophobic tails and hydrophilic heads.

Question 7

What is the main use of phospholipids?

Answer 7

Make up the bilayer of cell membranes

Question 8

What are some properties of phospholipids and how do they releate to their structure?

Answer 8

• Heads are hydrophilic and tails are hydrophobic, so they form a double layer
• The centre of the bilayer is hydrophobic, so water soluble substances can’t easily pass through