Fatty Acid Classification

Question 1

FAs are amphipathic:

Difference in structure between hydrophobic and hydrophilic parts of fatty acids

Answer 1

Hydrophobic- hydrocarbon chains

Hydrophilic- terminal carboxyl group with pKa ~4.8

Question 2

Terminal carboxyl of FAs has pKa ~4.8 so at physiological pH, what does it look like?

Answer 2

-COO-

Question 3

Long chain fatty acids are predominantly ___ so what do they need?

Answer 3

Hydrophobic; need association with proteins that help them be soluble in solution (serum albumin is an example)

Question 4

Difference between saturated and unsaturated fatty acids

Which has more energy associated with it?

Answer 4

Saturated- single bonds
Unsaturated- 1 or more double bonds (mono/poly)

Saturated (saturated with hydrogens which deliver electrons)

Question 5

What does the following to do melting temperature (Tm) and fluidity

1. Introduction of double bonds
2. Increasing chain length

Answer 5

1. Reduces Tm and increases fluidity

2. Increases Tm and decreases fluidity

Question 6

Carbon 1 is the
Carbon 2 is the 
Carbon 3 is the
Carbon 4 is the 
Terminal methyl group carbon is the

Answer 6

Carboxy carbon
Alpha carbon (carbon attached to the carbon of carboxyl group)
Beta carbon
Gamma carbon
Omega carbon 

(Keep in mind parenthesis when counting carbons)

Question 7

Is the following a omega 6 or omega 3 FA:

20:4 (5,8,11,14)

Answer 7

Omega 6 because 20-14=6. (Terminal double bond is 6 bonds in from the omega carbon)

Question 8

What two FAs do plants provide that humans cannot synthesis?

Are they omega 6 or omega 3?

Answer 8

Linoleic acid= omega 6

Alpha-linolenic acid = omega 3

Question 9

What happens if linoleic acid is deficient in diet?

Answer 9

Arachidonic Acid becomes essential (also an omega 6 FA)

Question 10

1. Linoleic acid is precursor for?
2. Arachidonic acid is substrate for?
3. Alpha-linolenic acid is precursor for?

Answer 10

1. Other shorter omega 6 FAs
2. Prostaglandin synthesis
3. Omega 3 fatty acids (important for growth and development)

Question 11

Structure of palmitic acid

Answer 11

16:0

Question 12

Give the length of the following:

1. Short and medium chain FAs
2. Long chain FAs
3. Very long chain FAs (and where they are synthesized)

Answer 12

1. 4-10 carbons (found in milk)
2. 16-22 carbons
3. > 22 carbons (synthesized in brain tissue)

Question 13

What are the two forms of fatty acids?

Answer 13

1. Free fatty acids (unesterified)

2. Fatty acyl esters (esterified fatty acids)

Question 14

Free fatty acids:

1. High level concentrations found in __, low level concentrations found in __
2. Point of origin (2)
3. Site of consumption
4. Uses (4)

Answer 14

1. High= blood serum during fasting; low= in most tissues
2. From TAG in adipose tissue and from circulating lipoproteins
3. Most tissues can take up FFAs
4. Structural components of membrane lipids (phospholipids/glycolipids/sphingolipids), conjugation to proteins for membrane anchoring properties, oxidized to provide free energy (adipose/muscle primarily), and precursors for hormone-like prostaglandins

Question 15

Fatty acyl esters:

1. Stored in?
2. Main function
3. 3 examples

Answer 15

1. Adipose tissue (as TAG)
2. Major energy reserve for the body
3. TAG, cholesteryl esters, and phospholipids