Fatty Acids & Lipids

Question 1

2 characteristics of lipids

Answer 1

• Low solubility in water
• Relatively hydrophobic

Question 2

9 function of lipids

Answer 2

1. Energy storage: good packing due to hydrophobic nature
2. Insulation from Environment: high heat capacity (can “absorb” heat)
3. Water repellant: hydrophobic nature
4. Bouyancy control & acoustics in in marine mammals
5. Membrane structure: main structure of cell membranes
6. Cofactors for enzymes: vit K - blood clot formation
7. Signaling molecules: growth factors, hormones
8. Pigments: colour of tomatoes, carrots
9. Antioxidants: Vit E

Question 3

Two major lipid categories

Answer 3

• Lipids that contain fatty acids (complex lipids)
• Lipids that dont contain FAs (cholesterol, vitamins, pigments)

Question 4

What categories can complex lipids be further divided into

Answer 4

• Storage lipids
• Membrane lipids

Question 5

What is the healthy kind of fat

Answer 5

Unsaturated fat - contains double bonds

Question 6

Which 2 fats are the unhealthy fats

Answer 6

1. Trans fats
2. Saturated fats

Question 7

Saturated fats

Answer 7

No double bonds between carbons in the alkyl chain

Question 8

Monounsaturated fats

Answer 8

One double bond between carbons in the alkyl chain

Question 9

Polyunsaturated fats

Answer 9

More than one double bond in the alkyl chain

Question 10

What would 18:1 delta 9 mean

Answer 10

• 18 carbons
• 1 double bond
• Double bond on 9th carbon from carbonyl carbon (COOH carbon)

Question 11

What does 18:1 omega 9 mean

Answer 11

• 18 carbons
• 1 double bond
• Double bond 9 carbons from the terminal methyl (last carbon)

Question 12

What happens when the length of hydrocarbon chain increases in FAs (2)

Answer 12

• The solubility of the FA in water decreases, as molecule is becoming more non polar, less able to form hydrogen bonds with water
• The melting point of the FA increases also

Question 13

What are the 2 major classes of polyunsaturated FAs

Answer 13

• Omega 6
• Omega 3
  (essential FAs)

Question 14

What does the cis configuration of double bonds do to the fatty acid chain

Answer 14

Kinks the chain

Question 15

What way do saturated FAs pack

Answer 15

In an orderly way - no d bonds = no kinks in chains

Question 16

What way do unsaturated FAs pack

Answer 16

Less orderly due to the kink (caused by double bond)

Question 17

Do unsaturated or saturated cis FAs have a lower melting point & why

Answer 17

Unsaturates cis FAs have a lower melting point as they are packed less tightly so require less energy to break, therefore they have a lower melting point

Question 18

By what process do trans fatty acids form

Answer 18

By partial dehydrogenation of unsaturated FAs

Question 19

Melting point of trans unsaturated FAs

Answer 19

A trans double bond does not form a kink.
Trans FAs can pack more tightly and therefore have higher melting points.

Question 20

What is a triglyceride

Answer 20

A lipid with 3 FAs esterified by a glycerol backbone

Question 21

Solubility of triglycerides in water compared to that of FAs

Answer 21

Less soluble in water than FAs due to esterification of carboxylate group

Question 22

What are waxes

Answer 22

Esters of long chain saturated & unsaturated FAs with long chain alcohols

Question 23

Solubility & melting point of waxes

Answer 23

• Insoluble
• High mp

Question 24

5 functions of waxes

Answer 24

1. Storage of metabolic fuel in plankton
2. Protection & pliability for hair & skin
3. Waterproofing of feathers
4. Prtection from evaporation in tropical plants
5. Used in lotions, ointments, polishes

Question 25

3 types of membrane lipid

Answer 25

1. Glycerophospolipid 2. Glycerolipid 3. Sterol - contains steroid rings

Question 26

Structure of glycerophospholipids

Answer 26

Two FAs form ester linkages with the 1st & 2nd hydroxyl groups of L-glycerol-3-phosphate * Head group substituent * Glycerol * Fatty acids

Question 27

What is the backbone of sphingolipids

Answer 27

The backbone of sphingolipids is long chain amino alcohol sphingosine

Question 28

In sphingolipids, the FA is joined to sphingosine via what kind of linkage

Answer 28

Amide linkage

Question 29

What are glycosphingolipids

Answer 29

A subgroup of sphingolipids that contain saccharide head groups

Question 30

Structure of sterols

Answer 30

* Four fused rings of steroid nucleus gives rigidity * Hydroxyl group (polar head) in A-ring * Non polar side chains

Question 31

Physiological role of sterols

Answer 31

* Cholesterol & related sterols in membranes of eukaryotic cells * Modulate fluidity & permeability * Thicken plasma membrane

Question 32

What are phospholipids degraded by

Answer 32

Phospholipases A-D Each cleaves a specific bond

Question 33

Where are structural & signalling lipids degraded

Answer 33

In the lysosome

Question 34

Examples of polyketides (biologically active lipids with medicinal uses)

Answer 34

* Erythromycin (antibiotic) * Amphotericin B (anti fungal) * Lovastatin (statin) - cholesterol lowering drugs