1.5: Lipids

Question 1

What characteristics do all lipids share (4)

Answer 1

1. They contain carbon, hydrogen, and poxygen
2. Proportion of oxygen:carbon:Hydrogen is smaller tan in carbs
3. They are insoluble in water
4. They are soluble in organic solvents e.g. Alcohol and acetone

Question 2

What are the two main groups of lipids

Answer 2

1. Triglycerides

2. Phospholipids

Question 3

Roles of lipids (5)

Answer 3

1. Phospholipids in cell membranes - contribute to flexibility
2. Waterproofing - insoluble so form a waxy coating
3. Insulation - Slow conductors of heat so insulate well. Also insulate the myelin sheath
4. Protection - Fat is stored around the kidney to protect it

Question 4

What is a triglyceride

Answer 4

3 fatty acids combined with 1 glycerol

Question 5

What bond is between glycerol and fatty acids

Answer 5

An ester bond formed in a condensation reaction

Question 6

Where do the differences in fats and oils come from

Answer 6

Variations in the fatty acids of triglycerides

Question 7

Types of triglycerides

Answer 7

1. Saturated
2. Mono-Unsaturated
3. Poly-unsaturated (Double bonding)

Question 8

How is the structure of triglycerides related to their properties (4)

Answer 8

1. Triglycerides have a high ratio of energy-storing carbon-hydrogen bonds to carbon atoms and are therefore an excellent source of energy
2. Low-mass to energy ratio - Good storage molecules because energy can be stored in a small volume
3. Large, non-polar molecules, triglycerides are insoluble in water. Storage doesnt affect water potential
4. high ratio of hydrogen to oxygen atoms, therefore they release water when oxidised

Question 9

What is a phospholipid

Answer 9

1 glycerol head, 2 fatty acid chains and 1 phosphate molecule

Same as triglyceride but one fatty aid is replaced with a phosphate molecule

Question 10

What is the unique property of phospholipids

Answer 10

1. The phosphate head is attracted to water (hydrophillic)

2. The fatty acid molecules repel water (Hydrophobic)

Question 11

What are the 2 parts a phospholipid is made of

Answer 11

1. A hydrophillic head - this interacts with water, but not with fat
2. A hydrophobic tail - this doesnt interact with water (repels) but mixes readily with fat

Question 12

What are phospholipids said to be

Answer 12

Polar

Question 13

How is the structure of phospholipids related to their properties (3)

Answer 13

1. Phospholipids are polar molecules, having a hydrophillic head and a hydrophobic tail. This means they form a bilayer between cell-surface membranes
2. Hydrophillic heads of phosholipid molecules help to hold at the surface of the cell-surface membrane
3. The phospholipid structure allows them to form glycolipids by combining with carbohydrates within the cell-surface membrane. These are important in cell recognition