Lipids

Question 1

What are two groups of lipids?

Answer 1

Triglycerides
Phospholipids

Question 2

How are Triglycerides formed?

Answer 2

The condensation of one molecule of glycerol and three molecules of fatty acid

Question 3

What bond does a condensation reaction between glycerol and a fatty acid form?

Answer 3

Ester bond

Question 4

How does Phospholipids molecules differ from Triglycerides?

Answer 4

One fatty acid is substituted by a phosphate-containing group

Question 5

What is the test for lipids?

Answer 5

Emulsion test
Ethanol

Question 6

What is the R-group?

Answer 6

Fatty acids which can be saturated or unsaturated

Question 7

What are lipids?

Answer 7

Biological molecules made of C, H and O which are only soluble in organic solvents such as alcohols

Question 8

What does the presence of double bonds change?

Answer 8

The name of the lipid
They can be saturated or unsaturated

Question 9

Where are saturated lipids found?

Answer 9

Animal fats

Question 10

Where are unsaturated lipids found?

Answer 10

Plants

Question 11

What does a double bonds do in terms of structure?

Answer 11

Allows molecule to bend
As a result, unsaturated fats cannot pack together as tightly and are therefore liquid at room temp

Question 12

Describe phospholipids heads and tails

Answer 12

Phosphate heads are hydrophilic (-charge)
Phosphate tails are hydrophobic
As a result, phospholipids form micelles when in contact with water
Therefore the molecule is polar

Question 13

How are phospholipids structure related to their properties?

Answer 13

• In an aqueous environment, being polar means a bilayer can be formed
• The hydrophilic heads can be used to hold at the surface of the cell surface membrane
• Their structure allows them to form glycolipids with carbohydrates which are importantly on the cell surface membrane for cell recognition

Question 14

How are triglycerides structure related to their properties?

Answer 14

• High ratio of energy storing C-H bonds to C atoms, therefore good energy store
• Low mass to energy ratio - good storage molecule with a lot of energy stored in a small volume - be ergo coal for animals as it is less mass to move around
• Large and non-polar lipids are insoluble in water so storage doesn’t affect water potential of cells
• High ratio of H-O atoms means triglycerides release water when oxidised, therefore provide important source of water for organisms to live in dry environments

Question 15

Describe saturated fatty acids

Answer 15

The hydrocarbon chain has only single bonds between C

Question 16

Describe unsaturated fatty acids

Answer 16

The hydrocarbon chain has at least one double bond between Cs