Lipids

Question 1

Triglycerids and phospholipids are what

Answer 1

two groups of lipids

Question 2

how are triglycerides formed

Answer 2

The condensation of one molecule of glycerol and three molecules of fatty acids.

Question 3

How is an ester bond formed?

Answer 3

-A condensation reaction between glycerol and a fatty acid

Question 4

How can you recognise a saturated or unsaturated fatty acid.

Answer 4

-The R group of a saturated fatty acid has no double bonds ( so carbons are fully saturated with H )

Question 4

Basic structure of lipids

Answer 4

Variable R group to the left

Question 5

Describe phospholipid structure ( related to function )

Answer 5

-heads are hydrophilic and tales are hydrophobic so they form a bilayer with heads out
-Phospholipids make up cell membrane of cell, cell membrane controls what enters/ leaves cell
-centre of bilayer is hydrophobic, so membrane acts as a barrier to water-soluble substances

Question 6

Describe the function of triglycerides ( related to function )

Answer 6

-Triglycerides are mainly used as energy storage molecules, they are good for this because:
>Long hydrocarbon tails of fatty acid contain lots of chemical energy which is released when they are hydrolysed
>Insoluble so don’t effect water potential of cell, good for storage, clump together as insoluble droplets as hydrophobic tails face inwards, shielding themselves with their glycerol head

Question 7

What is the physical difference between a phospholipid and triglyceride?

Answer 7

-In phospholipids, one of the fatty acids of a triglyceride is substituted by a phosphate-containing group

Question 7

Describe the emulsion test for lipids

Answer 7

-shake test substance with ethanol until it dissolves
-poor into water
-any lipid will show up as a milky emuslion
-(more lipid = more noticeable colour will be

Question 7

Which section of the phospholipid is hydrophobic, and which is hydrophillic?

Answer 7

-heads are hydrophilic and tales are hydrophobic