Lipids

Question 1

Biological functions of lipids

Answer 1

-Storage of energy - reduced compounds, hydrophobic nature
-Insulation from environment - low thermal conductivity, high heat capacity, mechanical protection
-Water repellent - hydrophobic
-Buoyancy control and acoustics in marine mammals
-Membrane structure
-Cofactors for enzymes - vit K for blood clot formation, coenzyme Q for ATP synthesis
-Signalling molecules
-Pigments
-Antioxidants - vit E

Question 2

What are carotenoids?

Answer 2

Lipids that can provide colour e.g canthaxanthin (bright red), Zeaxanthin (bright yellow)

Question 3

What are the 2 types of lipids that contain fatty acids?

Answer 3

Storage lipids (Glycerol and 3 fatty acids)
Mmembrane lipids - more complex

Question 4

What are the 3 types of membrane lipids and what can these be broken into

Answer 4

1. Phospholipids
   -Glycerophospholipids (Glycerol, 2 fatty acids, phosphate+alcohol)
   -Sphingolipids (Sphingosine, 1 fatty acid, PO4+choline
2. Glycolipids
   -Sphingolipids (Sphingosine, 1 fatty acid, mono or oligosaccharide
   -Galactolipids (sulfolipids) (Glycerol, 2 fatty acids, mono or disaccharide+(SO4)
3. Archael ether lipids (3 glycerols, 2 diphytanyl, 2 PO4)

Question 5

What are trans fats and give examples

Answer 5

Unsaturated fatty acids that have be modified in food processing and made bad for you
E.g Hydrogenated vegetable oils, fast foods, cakes/pastries, chocolate, deep fried food

Question 6

What are the 2 types of saturated fatty acids and give examples

Answer 6

-Have no double bonds
i) Vegetable fats - coconut, palm oil, 3 in 1 beverages, creamer, condensed milk
ii) Animal fats - poultry skin, fatty meat, butter, ghee, tallow lard, full cream dairy products

Question 7

What are unsaturated fatty acids, what are the 2 types and give examples

Answer 7

-Has double bonds and are good for you
i) Polyunsaturated fats - com oil, soybean oil, sunflower oil, seeds, cold water fish
ii) Monounsaturated - olive oil, canola oil, peanut oil, sesame oil, avocado, most nuts

Question 8

What is a fatty acid made up of?

Answer 8

Carboxylic acids (polar) with hydrocarbon chains (non polar) containing between 4-36 carbons
Almost all FAs have even no. of carbons
Most arev unbranched

Question 9

Delta numbering VS Omega numbering

Answer 9

Delta - decribes location of first carbon of the alkene (dbl bond) in relationship to the carbonyl carbon (carbon in carboxyl end)

Omega - describes location of first carbon of alkene in relation to terminal methyl (last carbon)

Question 10

As length of the fatty acid increases the melting point……..
solubility…………

Answer 10

Melting point increases if saturated (no dbl bonds) and decreases if number of double bonds increase as less tightly packed together
Solubility decreases as non polar hydrocarbon end is increasing as the chain is getting longer - hydrophobic effect is increasing

Question 11

What are the 2 main classes pf polyunsaturated fatty acids (PUFA)?

Answer 11

Omega - 3 and Omega - 6
Humans need them but cant synthesize them

Question 12

What is the conformation of fatty acids?

Answer 12

-Saturated chain tends to adopt extended conformations
-Double bonds in natural unsaturated fatty acids are mostly in cis configuration which kinks the chain

Question 13

How do trans fatty acids form and what are their characteristics?

Answer 13

-By partial dehydrogenation of unsaturated fatty acids
-Done to increase shelf life or stability at high temps pf poils used in cooking
-Trans fatty acids can pack more and show higher melting points

Question 14

What can consuming trans fats increase the risk of?

Answer 14

Cardiovascular disease

Question 15

What is the principal trans unsaturated fatty acid?

Answer 15

Elaidic acid

Question 16

Fats VS Oils

Answer 16

fats - solid
oils - liquid

Question 17

Are triglycerides more or less soluble in water than fatty acids? Why?

Answer 17

Triglycerides are less soluble in water than fatty acids due to esterification of carboxylate group

Question 18

Advantages of fats over polysaccharides?

Answer 18

-FAs carry more energy per carbon because they are more reduced
-FAs carry less water per gram as they are non polar

Question 19

What are waxes?

Answer 19

Esters of long-chain saturated and unsaturated fatty acids with long chain alcohols

Question 20

Solubility and melting points of waxes?

Answer 20

Insoluble and have high melting points

Question 21

Functions of Waxes?

Answer 21

-Stprage of metabolic fuel in plankton
-protection and pliability for skiin and hair in vertebrates
-waterproofing of feathers in birds
-protection from evaporation in tropical plants and ivy
-used in lotions, ointments, polishes

Question 22

What are 3 types of membrane lipids?

Answer 22

-glycerophospholipid
-glycolipid
-sterol

Question 23

How do glycerophospholipids (phosphoglyceride) form?

Answer 23

-2 fatty acids form ester linkages with the first and second hydroxyl group of L-glycerol-3-phosphate (L-hydroxyl group on left, 3- 3C has phosphate)

Question 24

What is the head group in glcerophospholipids?

Answer 24

The highly polar phosphate group may be further esterified by an alcohol - such substituent groups are called the head groups

Question 25

What are 2 glycerophospholipids that are found in the membrane?

Answer 25

-Phosphatidylcholine (PC) - major component of eukaryotic cell membranes
-Phosphatidylserine (Pts) - early biomarker of apoptotic cell death

Question 26

How does phosphatidylserine indicate cell death?

Answer 26

In healthy cells there is no PTS found on outer membrane only inner membrane
Early stage apoptosis - PTS found flipped onto outer membrane

Question 27

How is a fatty acid joined to a sphingosine?

Answer 27

Via an amide linkage (not an ester linkage)

Question 28

How is a polar head group connected to a sphingosine and where are glycosphingolipids found?

Answer 28

A polar head group is connected to sphingosine by a glycosidic or phosphodiester linkage
- The sugar-containing glycosphingolipids are found in outer surface of plasma membranes

Question 29

What is the backbone of a sphingolipid?

Answer 29

A long chain amino alcohol called a sphingosine

Question 30

Where would you find i) Sphingomyelin ii)Gangliosides

Answer 30

Sphingomyelin - found on myelin sheaths
Gangliosides - within cells of CNS

Question 31

What are the blood groups determined by?

Answer 31

The type of sugars loacted on the head groups in glycosphingolipids
e.g N-acetylgalactosamine for A blood group
D-galactose for B blood group

Question 32

What enzyme creates the expression for the structure of sugar on the head groups of glycosphingolipids for blood groups?

Answer 32

Glycosyltransferase

Question 33

What antigen will individuals with no active glycosyltransferase have?

Answer 33

The O antigen

Question 34

Where is cholesterol found and what are its functions?

Answer 34

-Found in membranes of most eukaryotics - not in bacteria
-Func: modulate fluidity and permeability, thicken plasma membrane

Question 35

What is tested for to check cholesterol levels - if too high?

Answer 35

Low- density lipoproteins - tend to deposit and clog arteries

Question 36

What are phospholipids degarded by?

Answer 36

Phospholipases A-D each cleaves a specfic bond
(Degrade gangliosides)

Question 37

What can failure to correctly degrade gangliosudes result in?

Answer 37

-Build up of lipids in lysosomes, dysfunction categorized as ‘lysosomal storage disorders’
e.g Batton disease, gauches disease- affect neurological system

Question 38

What are polyketides?

Answer 38

Biologically active lipids with medicinal uses e.g erythromycin
e.g lovastatin- lower cholesterol