Lipids

Question 1

1. What elements are lipids made up from?

Answer 1

Carbon, hydrogen and oxygen, but less oxygen and more hydrogen than carbohydrates

Question 2

2. What are the main types of lipid?

Answer 2

The 2 main types are triglycerides and phospholipids but they also include waxes and steroids

Question 3

3. What are the main jobs of triglycerides?

Answer 3

• They act as energy stores (release more kJ/g than carbs when hydrolysed) * They are excellent for insulation purposes as they are non-conductive (we store this fat as sub-cutaneous fat beneath the skin) * This layer of fat also acts to protect many major organs in the body

Question 4

4. How are triglycerides formed?

Answer 4

They are formed when one glycerol molecule combines with 3 fatty acid via 3 condensation reactions (water removed)

Question 5

5. What type of bond is found in triglycerides and where is it found?

Answer 5

ESTER BONDS are formed between the hydroxyl, -OH ,groups of the glycerol and the carboxyl, -COOH, groups of the 3 fatty acid chains

Question 6

6. How is energy released from a triglyceride?

Answer 6

During digestion, hydrolysis occurs, breaking the ester bonds and releasing energy (forming the glycerol and 3 fatty acids once more)

Question 7

7. What is the difference between saturated and unsaturated fatty acids?

Answer 7

Saturated fatty acids contain the maximum number of hydrogen atoms and therefore no C=C double bonds. Unsaturated fatty acids do not have the maximum number of hydrogen atoms and so DO HAVE C=C double bonds.

Question 8

8. What are mono and polyunsaturated fats?

Answer 8

Monounsaturates have ONE C=C bond, polyunsaturates have more than one C=C bond

Question 9

9. What is the different between fats and oils?

Answer 9

Fats tend to be solid at room temperature and are often made from saturated fatty acids; oils tend to be liquid at room temperature and tend to be made from unsaturated fatty acids

Question 10

10. How is a phospholipid different to a triglyceride?

Answer 10

Trigylcerides are made up of one glycerol molecule and 3 fatty acids, phospholipids are made up of one glycerol molecule attached to 2 fatty acids and one phosphate group, in other words one of the fatty acid chains is replaced by a phosphate group

Question 11

11. Explain the terms, hydrophobic and hydrophilic in relation to phospholipids

Answer 11

The head end of the phospholipid, containing the glycerol and the phosphate group is HYDROPHILIC, meaning it is attracted to water and is “water-loving”. It is also POLAR (or charged) The tail end of the phospholipid, containing the fatty acid chains is HYDROPHOBIC and repels water, it is “water-hating”. It is non-polar.

Question 12

12. What is the job of phospholipids in the body?

Answer 12

• They form the phospholipid bilayer which is what cell membranes are made from * They are found in a fluid in the lungs called, surfactant, which prevents the lungs from collapsing

Question 13

13. In what different ways do phospholipids arrange themselves when exposed to water

Answer 13

1. On the surface of water they form a monolayer 2. When mixed with water they form micelles 3. When forming cell membranes, they form a bilayer