Wee 6 Structure And Function Of Lipids

Question 1

Lipids

Answer 1

Biological lipids
-Chemically diverse
-Functionally diverse

• Defining feature – insolubility in water

Question 2

Storage lipids

Answer 2

Fats & oils principle form of stored energy for organisms -Are derivatives of fatty acids

• Fatty acids – hydrocarbon derivatives
  -Triglycerides & waxes contain fatty acids

Highly exogonic

Question 3

Fatty acids

Answer 3

Carboxylic acids
Hydrocarbon chains 4 to 36 carbons long (C4 to C36)
Chains can be saturated (no double bonds) or unsaturated (contains double bonds)

Question 4

Fatty acid nomenclature

Answer 4

Palmitic acid is abbreviated as 16:0

First carbon attached to carboxiliac end

Oleic acid is abbreviated as 18:1D9
Denotes position of double bond
Double bond Found at postion 9

Question 5

Isomerism

Answer 5

Trans c are opposite sides of the double bind

Question 6

Polyunsaturated fatty acids (PUFAs)

Answer 6

Omega-3 (ω-3) fatty acids important role in nutrition
- Termed so due to position of double bond
- Double bond nearest methyl end is important so can label from that end
- Omega-6 fatty acids – double bond between carbon 6 & 7 From methyl end
(Opposite from carboxylic end )

Question 7

Omega-3 fatty acids

Answer 7

umans require but lack ability to synthesise α-linolenic acid (ALA; 18:3D9,12,15)
Must obtain from diet

-From ALA can synthesise
— Eicosapentaenoic acid (EPA; 20:5D5,8,11,14,17)
— Docosahexaenoic acid (DHA; 22:6D4,7,10,13,16,19)
Chia, walnuts, kiwi seeds

Imbalance of omega-6 & -3 can = risk of CVD
- Optimal ratio omega-6 to -3, 1:1 to 4:1  Ratio in N.
—American diets, 10:1 to 30:1
—‘Mediterranean diet’ rich in omega-3

Question 8

Fatty acids

Answer 8

Physical properties
—Determined by length & degree of unsaturation
— Solubility – longer the chain & fewer the double bonds = lower solubility in water

Melting point – greater number of unsaturated/double bonds
—Lower melting point
— Double bonds = ‘kink’ in tail = reduced packing of fatty acids

Glucose Oxygen is electronegative = pull electrons towards it leaving hydrogen electro postive = solubility in h20 is higher

Saturated fatty acids = lots together, van de waals bonds

Unsaturated fatty acids kinks = unable to line up, Limited van de waals bonds, less heat to melt it

Question 9

Triglycerides

Answer 9

Also known as triacylglycerols, fats or neutral fats

—Triglyceride structure = 3 fatty acids, 3 ester bonds, 1 glycerol

Non polar = hydrophobic, insoluble in water

Triglycerides provide stored energy & insulation
—Form separate phase in aqueous cytosol – droplets of metabolic fuel
— Adipocytes store fat droplets (nuclei pushed out to edge of plasma membrane)(not many mitochondria)

Question 10

Energy from fats

Answer 10

Fats = 9 cal per gram, not many o2, highly reduced, don’t carry water as there insoluble
Protien = 4 cal per gram
Carbs = 4 cal per gram

Question 11

Storage from fats

Answer 11

White adipose under are skin
Acts as insulation

Question 12

Partial Hydrogenation of cooking oils

Question 13

Hydrogenation of oleic acid

Question 14

Wax

Answer 14

Biological waxes – esters of long chain fatty acids (c14 – C36) + long chain alcohols (c16 – C30)

Insoluble due to the lack of oxygen