Lipid Classification

Question 1

Structure of Fatty Acids

Answer 1

• amphipathic molecules
• Hydrophobic:hydrocarbon chains
• Hydrophilic: Terminal carboxyl group (pka 4.8)
• solubility depends on length(longer chain is less soluble)

Question 2

At physiological pH

Answer 2

• Cooh ionizes to COO- and is hydrophilic
• long chain fatty acids (LCFA) are predominantly hydrophobic and must be associated with a protein for circulation solubility

Question 3

Saturated fatty acid

Answer 3

• no double bonds

- maximal saturation with H

Question 4

Unsaturated fatty acid

Answer 4

• carbons have 1 or more double bonds

- double bonds: cis formation, cause kinks, spaced at 3 carbon intervals

Question 5

melting temp

Answer 5

• double bonds lower the melting temp and increase fluidity
• increasing chain length increases melting temp and decreases fluidity
• membrane phospholipids typically have LCFA and contain a lot of double bonds to attempt to increase fluidity

Question 6

Carbon naming

Answer 6

Carbon 1: the carboxyl carbon
Alpha carbon: Carbon 2: the carbon to which the carboxyl group is attached.
Beta carbon: Carbon 3
Gamma Carbon: carbon 4
Omega carbon: terminal methyl group carbon(independent of length)

Question 7

Arachidonic acid

Answer 7

20: 4(5,8,11,14)
- omega 6 fatty acid
- terminal doble bond is 6 bonds away from the omega carbon

Question 8

Determine is omega 3 or 6

Answer 8

• count the number of bonds
• the first double bond occurs from where from the omega carbon?
• so if 20 and first double bond is 6 away, its an omega 6

Question 9

Essential fatty acids

Answer 9

• plants provide 2 fatty acids humans cannot synthesize
• Linoleic acid and alpha linolenic acid
• Arachidonic acid becomes essential IF linoleic acid is deficient in the diet

Question 10

Why are they fatty acids?

Answer 10

• linoleic acid is a precursor for other shorter omega 6 FA
• Arachidonic acid is a substrate for prostaglandin synthesis
• alpha linolenic acid is precursor for omega 3 fatty acids: important for growth and development

Question 11

Fatty acid length

Answer 11

-short and medium: 4-10(start at 4 because thats when it is considered a fatty acid)
-Long chain: 16-22
Very long: greater than 22

Question 12

Free fatty acids vs fatty acyl esters

Answer 12

• free fatty acids: unesterified

- fatty acyl esters: esterified

Question 13

Free fatty acids

Answer 13

• low level concentrations of them found in tissues (they are insoluble so you dont want a whole lot)
• high levels after fasting (protein blocks albumin)

Question 14

Transport of long fatty acids in blood serum

Answer 14

• requires albumin

- short chains dont need that shit

Question 15

Point of origin of free fatty acids

Answer 15

• From TAG in adipose tissue
• from circulating lipoproteins
• Site of consumption: most tissues can take up free fatty acids(adipose and muscle the most)

Question 16

Use of free fatty acids

Answer 16

1. structural component of membrane lipids
   
   • phospholipids and glycolipids and sphingolipids
2. conjugation to proteins for membrane anchoring properties
   
   • hold hydrophobi kids without killing them
3. oxidized to provide energy
   
   • mostly in liver and muscle
4. precursors for hormone-like prostaglandins

Question 17

Fatty Acyl esters

Answer 17

• precursors used to form more complex molecules (TAG)
• stored in adipose tissues as TAG
• serve as the major energy reserve
• 90% of plasma fatty acids are fatty acid esters contained in lipoprotein particles
  - TAG
  - Cholesteryl esters
  - Phospholipids