L17 Omega-3 and Omega-6 Fatty Acids

Question 1

What is each number/letter representative of in PUFA nomenclature?
22:5n-3

Answer 1

22 - number of carbon atoms in the chain
5 - number of double bonds in the carbon chain
n-3 - position of the first double bond from the methyl/omega/terminal end

Question 2

What are the essential fatty acids? (2)

Answer 2

Omega 3
Omega 6

Question 3

What is omega 3 also known as?

Answer 3

Alpha-linolenic acid

Question 4

What is omega 6 also known as?

Answer 4

Linoleic acid

Question 5

What essential fatty acid has the nomenclature 18:3n-3?

Answer 5

Omega 3/Alpha-Linolenic Acid

Question 6

What essential fatty acid has the nomenclature 18:2n-6?

Answer 6

Omega 6/Linoleic Acid

Question 7

What does ‘essential fat’ mean?

Answer 7

Can not be synthesised in the body and is required from the diet

Question 8

What are the two sources of PUFAs?

Answer 8

Omega-3 (ALA) and Omega 6

Question 9

What is the class of monounsaturated fats?
What are some examples? (4)

Answer 9

Omega 9 fatty acids
- Olive oil
- Avocado
- Peanuts
- Almonds

Question 10

What are some examples of Omega-6 FAs? (3)

Answer 10

• Corn oil
• Safflower oil
• Sunflower oil

Question 11

What are some examples of ALA FAs? (3)

Answer 11

• Eicosapentanoic acid (fish, shellfish)
• Docosahexanoic acid (fish, shellfish)
• Alpha linolenic acid (flaxseed, soybean, walnut, rapeseed oils)

Question 12

What PUFA is consumed more in a Western diet and by how much?

Answer 12

Omega-6 is consumed ~20x more than Omega-3

Question 13

What is the major plant-based oil produced in the world?

Answer 13

Palm oil

Question 14

What is the main type of fat in coconut oil?

Answer 14

Saturated fat

Question 15

What is the main type of fat in olive oil?

Answer 15

Monounsaturated fat - Oleic acid (Omega 9)

Question 16

How are the essential fatty acids stored in the body?

Answer 16

Esterified to phospholipids and stored in the lipid bilayer of plasma and nuclear membranes

Question 17

How is diet related to the composition of cellular phospholipids?

Answer 17

• Omega 6 and omega 3 have competitive pathways
• These essential fatty acids (attained by the diet) are stored in the phospholipid cell membrane therefore what is consumed is what is stored

Question 18

What is EPA?

Answer 18

Eicosapentaenoic acid - LC Omega 3 PUFA

Question 19

What is DHA?

Answer 19

Docosahexaenoic acid - LC Omega 3 PUFA

Question 20

How do EPA and DHA contribute to cellular membrane function? (4)

Answer 20

• Fluidity
• Membrane protein function
• Generation of intracellular signalling molecules
• Gene expression

Question 21

What are the key cell types in which PUFAs play a role? (3)

Answer 21

• Neural
• Endothelial
• Platelets

Question 22

What are eicosanoids? (1) What do they do? (1)

Answer 22

• Biologically active lipids
• Act as signalling molecules (localised hormones)

Question 23

Do cells store eicosanoids? Why or why not?

Answer 23

Cells do not store eicosanoids
They are synthesised when required from fatty acids in cell and nuclear membranes

Question 24

What are some key eicosanoids? (3)

Answer 24

• Prostaglandins (produced by the prostate gland)
• Leukotrines (produced by leukocytes)
• Thromboxanes (produced by platelets; thrombocytes)

Question 25

What is arachidonic acid?

Answer 25

Omega 6 PUFA

Question 26

What is the recommended Omega 6 to Omega 3 ratio?

Answer 26

2:1 (Omega 6 to Omega 3)

Question 27

What are some benefits of omega-3 fatty acids? (5)

Answer 27

- Anti-inflammatory effects - Membrane stabilising effects - Anti-thrombotic effects - Lipid lowering effects - Plaque stabilisation effects

Question 28

a) What is PGE2? (1) b) What effects can it have on the body? (5)

Answer 28

a) Prostaglandin E2 is a pro-inflammatory mediator from eicosanoids (arachidonic acid) b) Effects on the body: - Induces fever - Increases vascular permeability -Increases vasodilation - Causes pain - Increases production of other inflammatory mediators

Question 29

a) What is LTB4? (1) b) What effects can it have on the body? (5)

Answer 29

a) Leukotriene B4 is a pro-inflammatory mediator from eicosanoids (arachidonic acid) b) Effects on the body: - Increases vascular permeability - Enhances local blood flow - Chemotactic for leukocytes - Increased leukocytes ROS production - Increases production of other inflammatory mediators

Question 30

What is the role of eicosanoids in platelet aggregation?

Answer 30

Thromboxanes are the major eicosanoids produced by platelets Initiates thrombus formation at sites of vascular injury or atherogenic plaque rupture

Question 31

What are some potential health benefits of ALA? (2)

Answer 31

- Lower risk of CVD (cardioprotective) - Lowering risk of cognitive impairment

Question 32

What is the order of priority of fat consumption?

Answer 32

1. Omega-3 PUFA 2. Omega 6 PUFA 3. MUFA 4. Saturated FA 5. Trans saturated FA