3.1.3 Lipids

Question 1

Saturated vs unsaturated

Answer 1

Saturated fats lack double bonds between the individual carbon atoms, while in unsaturated fats there is at least one double bond in the fatty acid chain.

Question 2

Explain how the structure of phospholipids makes them able to form a bilayer

Answer 2

Phospholipids heads a hydrophilic and their tails are hydrophobic, so they form a double layer with their heads facing outwards the water on either side. The center of the bilayer is hydrophobic so water soluble substances can’t easily pass through it - the membrane acts as a barrier to those substances

Question 3

Compare and contrast the structure and properties of phospholipids with those of triglycerides

Answer 3

Both types of molecule contains glycerol contain ester bonds and contain the elements carbon hydrogen and oxygen but phospholipids also contain phosphorus. The fatty acids contained in both types of molecule may be saturated or unsaturated. Both are insoluble in water because of these fatty acid chains. In contrast phospholipids have two fatty acid chains and phosphate groups versus triglyceride three fatty acid chains. Phospholipids have a hydrophilic region as well as a hydrophobic region while triglycerides are entirely hydrophobic and because of this phospholipids form micelles or bilayers when in solution which is something triglycerides do not do

Question 4

Give two reasons why triglycerides are used as energy storage molecule

Answer 4

Their long hydrocarbon tails of fatty acids contain lots of chemical energy

Question 5

What are phospholipids

Answer 5

The major components of cell surface membranes. They have fatty acid tails that are hydrophobic and a phosphate head, that is hydrophilic, attached to a glycerol molecule.

Question 6

What is the bond formed when fatty acid molecules are joined to a glycerol molecules in a condensation reaction?

Answer 6

Ester

Question 7

Glycerol

Answer 7

The formula for glycerol is C3H8O3. It has 3 carbon (C) atoms, 8 hydrogen (H) atoms, and 3 oxygen (O) atoms.

Question 8

What are triglycerides?

Answer 8

• 3 fatty acids and 1 glycerol
• Have a higher ratio of energy storing carbon atoms and are therefore an excellent source of storage
• Have low mast energy ratio making them good storage molecules because much energy can be stored in a small volume
• Large no polar molecules make them insoluble as a result their storage does not affect osmosis in cells or the water potential of them
• As they have a high ratio of H to O atoms they release Water when oxidized and therefore provide an important source of water especially for organisms in dry deserts

Question 9

What are lipids?

Answer 9

Lipids are a group of organic compounds composed mostly of carbon and hydrogen including a proportionately smaller amount of oxygen
Are insoluble in water
Serve as a source of stored energy
Component of cell membrane

Question 10

What are the two groups of lipids

Answer 10

Triglycerides
Phospholipids

Question 11

Explain the difference between a saturated fatty acid and unsaturated fatty acid

Answer 11

Saturated fatty acids don’t have any double bonds between their carbon atoms where I saturated do

Question 12

R Group of a fatty acid may be

Answer 12

Saturated or unsaturated

Question 13

What bond does a reaction between glycerol and a fatty acid (RCOOH)

Answer 13

Ester

Question 14

Fatty acid versus phosphate molecule

Answer 14

Fatty acid - hydrophobic
Phosphate molecules - hydrophilic