1: BIOLOGICAL MOLECULES - LIPIDS

Question 1

What are the 2 types of lipid?

Answer 1

-triglycerides
-phospholipids

Question 2

What molecules are triglycerides made up of?

Answer 2

• 1 molecule of glycerol
• 3 molecules of fatty acids

Question 3

What is the basic structure of a fatty acid?

Answer 3

R–COOH

Question 4

What does hydrophobic mean?

Answer 4

repels water

Question 5

What is the R group in a fatty acid?

Answer 5

hydrophobic tail made of hydrocarbons that make lipids insoluble in water

Question 6

What are the 2 types of fatty acid?

Answer 6

• saturated
• unsaturated

Question 7

What is the difference between saturated and unsaturated fatty acids?

Answer 7

• saturated fatty acids dont have any double bonds between carbon atoms
• unsaturated fatty acids have double bonds between carbon atoms which causes the hydrocarbon chain to kink

Question 8

How are triglycerides formed?

Answer 8

• condensation reactions
• ester bond forms between the glycerol and fatty acids and a molecule of water is released for each ester bond formed

Question 9

What is the function of a triglyceride and how does their structure relate to this function?

Answer 9

• used as energy storage molecules
• fatty acid tails contain lots of chemical energy so when theyre broken down a lot of energy is released
• insoluble in water so they dont affect water potential and cause lysis
• form insoluble droplets as fatty acid tails are hydrophobic (tails face inwards and shield themselves with glycerol)

Question 10

What are phospholipids made up of?

Answer 10

• 1 molecule of glycerol
• 2 molecules of fatty acids
• a phosphate group

Question 11

What does hydrophilic mean?

Answer 11

attracts water

Question 12

Is the phosphate group in a phospholipid hydrophobic or hydrophilic?

Answer 12

hydrophilic

Question 13

Where are phospholipids found?

Answer 13

cell membranes

Question 14

What is the function of a phospholipid and how does their structure relate to this function?

Answer 14

• make up bilayer of cell membranes
• phospholipid heads are hydrophilic and their tails are hydrophobic so they form a double layer with their heads facing out towards water on either side
• the centre of the bilayer is hydrophobic so water-soluble substances cant easily pass through it. the membrane acts as a barrier

Question 15

How do you test for lipids?

Answer 15

emulsion test
- shake substance with ethanol for ~1 min
- pour solution into water
- any lipid will appear as milky emulsion (the more lipid there is, the more noticeable the milky colour will be)