6: Nutritional Properties Of Lipids

Question 1

How is energy generation achieved from fatty acids?

Answer 1

Through the process of beta oxidation, which takes place in mitochondria of cells.

Question 2

Explain the process of beta oxidation

Answer 2

TGs broken down to FFA which are transported into cells mitochondria using Carnitine (molecule that shuttles FFA into mitochondria from cytoplasm).
Energy generation occurs in mitochondria by FFA being broken down by the sequential removal of 2 carbon units. These are released in the form of acetyl COA which feed into the TCA cycle (citric acid cycle) = energy generation

Question 3

Explain how membrane fluidity is regulated

Answer 3

• Fatty acid composition :
  Saturated FA reduce fluidity
  Long chains reduce fluidity
  Cis unsaturated FA produce a kink = increased fluidity
• Cholesterol:
  (Sits between FA in membranes)
• Prevents crystallisations as stops interactions between adjacent FA (increased fluidity)
• Blocks large motions of acyl chain (acts as a barrier) = reduces fluidity

Question 4

Explain why we need essential fatty acids

Answer 4

n-3 and n-6 (omega 3 & 6) FA structure cannot be synthesised by humans as we lack the desaturase enzyme, and so dietary sources are required.
- Involved in regulating cell membrane structure
- n-3:n-6 ratio important
- important in synaptic function in the brain and visual development
- Precursors for a range of other signalling molecules, e.g. Eicosanoids : regulate inflammation & immunity

Question 5

Give dietary sources of omega 3 & omega 6 PUFA

Answer 5

n-3 PUFA = fish oils (EPA and DHA) & flax/linseed/rapeseed oil (a linolenic acid)
n-6 PUFA = vegetable oils (linoleic acid)

Question 6

Give food sources of saturates

Answer 6

Animal products (meat, cheese, butter)
Coconut

Question 7

Give food sources of monounsaturated fat

Answer 7

Olives; veg oils; spreading fats; nuts; avocados

Question 8

Give food examples of polyunsaturates

Answer 8

Cereals; fish; plant oils; spreading fats

Question 9

Give food sources of trans unsaturated fats

Answer 9

Meat/dairy products; processed foods; spreading fats

Question 10

What are the health implications of excessive fat intake (particularly saturates)?

Answer 10

• Hyperlipidaemia
• CVD
• obesity
• diabetes mellitus
• cancer : breast, colon, prostate

Question 11

What is the % daily population average intake of fat (recommended fat intake)?

Answer 11

33% - assuming 5% from alcohol and 15% from protein