Unit 2 - A. Fatty Acids

Question 1

Structural properties of fatty acids

Answer 1

• long hydrocarbon chain with a carboxylic acid at one end
• chain length usually 12-20
• Even-number length used in human body (odd # can be metabolized for energy but not really used biological synthesis)

Question 2

Saturated fatty acid

Answer 2

no carbon=carbon double bonds

Question 3

Monounsaturated F.A.

Answer 3

One carbon=carbon double bond

Question 4

Polyunsaturated F.A.

Answer 4

More than one carbon=carbon double bond (up to 6)

Question 5

Omega-6 Fatty Acids

Answer 5

• polyunsaturated F.A.
• counting carbons from terminal methyl to COOH, there is a C=C at the 6th carbon-carbon bond
• abundant in vegetable oils, corn, safflower, sunflower, and soybean oils; wheat germ, nuts, seeds, fat from pigs and poultry.
• examples: linoleic acid, arachidonic acid

Question 6

Omega-3 Fatty Acids

Answer 6

• polyunsaturated F.A.
• same counting as omega-6 with C=C at the 3rd C-C bond
• abundant in fatty fish that eat plant fatty acids, flax seeds and walnuts.
• examples: EPA and DHA

Question 7

Biological effects of Omega fatty acids

Answer 7

Omega-6 fatty acids - in place of saturated fat leads to lower serum cholesterol levels and lower risk for CVD

Omega-3 fatty acids:

1. Anti-inflammatory effects
   - decreases arachidonic acid (source of pro-inflammatory eicosanoids)
   - inhibits Rho-kinase (that regulates pro-inflammatory biomolecules)
2. Inhibition of platelet aggregation
3. Decrease TG/Lipoproteins synthesis
   - decrease activity of sterol receptor-binding protein-1c
   - activates PPAR-alpha to increase oxidation of F.A.
4. Interferes with plaque stabilization
   - decreases activation of endothelial cells and infiltartion of macrophages
   - decreases MMP (involved with plaque stability)
5. Prevents/lowers dementia risk
6. Prevents colorectal cancer

Question 8

Solubility of F.A.

Answer 8

• “like dissolves like”
• long hydrocarbon chain predominates over polar COOH = nonpolar molecule
• soluble in nonpolar solvents (ether, acetone, cyclohexane)
• insoluble in water

Question 9

Melting points of F.A.

Answer 9

• longer chain, increases M.P.
• saturated, increases M.P.
• more contact strengthens intermolecular forces (van der waal’s forces) and the ability to pack close together

Question 10

Fatty Acid Biosynthesis

Answer 10

• requires Acetyl CoA and occurs in the cytoplasm catalyzed by multi-enzyme complex F.A. synthase.
• Mitochondria: pyruvate -> acetyl CoA
• Acetyl CoA is converted to citrate to be moved to cytoplasm (catalyzed by citrate lyase)
• End of enlongation produces palmitoyl CoA

Question 11

Fates of Palmitoyl CoA

Answer 11

1. Esterification to glycerol + 2 more F.A. = triglyceride

2. Elongation / desaturation to make other F.A.

Question 12

Elongation of palmitoyl CoA

Answer 12

• occurs in the ER of Eukaryotes
• most tissues= elongate until 18 carbon stearate (stearoyl-CoA)
• Brain = elongate until 24 carbon chains for incorporation into sphingolipids

Question 13

Desaturation of palmitoyl CoA

Answer 13

• converts saturated fatty acids to unsaturated
• Ex: stearoyl CoA desaturase introduced double bond between C9 and C10 (palmitic acid = palmitoleic acid ; stearic acid = oleic acid)
• humans lack enzymes to produce bonds beyond C9 so F.A. like linoleic/linolenic acid must come from our diet = Essential F.A.

Question 14

Increase F.A. Biosynthesis

Answer 14

• excess kcal
• high proportion of carbohydrates
• insulin

Question 15

Decrease F.A. Biosynthesis

Answer 15

• restricted caloric intake
• high proportion of fat
• deficiency of insulin