Lipids

Question 1

How are lipids different from proteins and carbohydrates?

Answer 1

They are not polymers formed from long chains of monomers.

Question 2

What do all lipids contain?

Answer 2

Hydrocarbons.

Question 3

What are hydrocarbons?

Answer 3

Molecules that contain only hydrogen and carbon atoms.

Question 4

What are the two types of lipids?

Answer 4

Triglycerides.

Phospholipids.

Question 5

What are triglycerides made up of?

Answer 5

One molecule of glycerol with three fatty acids attached to it.

Question 6

What are the fatty acids in triglycerides made of?

Answer 6

The fatty acids have long tails made of hydrocarbons.

Question 7

Why are triglycerides insoluble in water?

Answer 7

The tails are hydrophobic.

Question 8

Define hydrophobic.

Answer 8

Repels water molecules.

Question 9

What is the structure of fatty acids?

Answer 9

They all contain the same basic structure (COOH), but the hydrocarbon tail varies.

Question 10

What are the two kinds of fatty acids?

Answer 10

Saturated fatty acids.

Unsaturated fatty acids.

Question 11

What is a saturated fatty acid?

Answer 11

Doesn’t have any double bonds between the carbon atoms. It is saturated with hydrogen.

Question 12

What is an unsaturated fatty acid?

Answer 12

Has double bonds between the carbon atoms, which causes the chain to kink.

Question 13

How are triglycerides formed?

Answer 13

Condensation reactions.

Question 14

What bond forms between the glycerol and a fatty acid when a triglyceride is formed?

Answer 14

Ester bond.

Question 15

Where are phospholipids found?

Answer 15

Cell membranes.

Question 16

What are phospholipids made up of?

Answer 16

A glycerol molecule with a phosphate group and two fatty acids attached to it.

Question 17

What is the phosphate group in phospholipids?

Answer 17

Hydrophilic.

Question 18

Define hydrophilic.

Answer 18

Attracts water molecules.

Question 19

What are the fatty acids in phospholipids?

Answer 19

Hydrophobic.

Question 20

What are triglycerides mainly used as?

Answer 20

Storage molecules.

Question 21

Why are triglycerides good storage molecules?

Answer 21

The long hydrocarbon tails of the fatty acids contain lots of chemical energy - a load of energy is released when they’re broken down.

Question 22

What do triglycerides bundle together as?

Answer 22

Insoluble droplets in cells because the fatty acid tails are hydrophobic - the tails face inwards, shielding themselves from water with their glycerol heads.

Question 23

What do phospholipids make up?

Answer 23

The bilayer of cell membranes.

Question 24

What do cell membranes do?

Answer 24

Control what enters and leaves a cell.

Question 25

Why to phospholipids form a double layer?

Answer 25

Phospholipid heads are hydrophilic and their tails are hydrophobic, so they form a double layer with their heads facing out towards the water on either side.

Question 26

How does the membrane act as a barrier to water-soluble substances?

Answer 26

The centre of the bilayer is hydrophobic, so water-soluble substances can’t easily pass through it.

Question 27

What is the test for lipids?

Answer 27

The Emulsion Test.

Question 28

How do you carry out the emulsion test?

Answer 28

Shake the test substance with ethanol for about a minute, then pour the solution into water.
Any lipid will show up as a milky emulsion.