Ch 5 - Lipid Structure and Function

Question 1

Phospholipids

Answer 1

• phosphate, alcohol on polar head
  
  • glycerol is a common alcohol
• hydrophobic fatty acid tail
• joined by phosphodiester linkages
• examples: phosphoglycerides and sphingolipids
  
  • not all sphingolipids are phospholipids

Question 2

Saturation

Answer 2

• hydrocarbon chains vary in length and saturation
• saturated fatty acid - only single bonds, no pi bonds, 4 bonds per carbon
  
  • greater van der waals forces and more stable structure
  • solid at room temperature
• unsaturated fatty acids - one or more double bonds
  
  • kinks in chain, difficult to stack and solidify
  • ex. olive oil

Question 3

glycerophospholipids

Answer 3

• contain glycerol attached to 2 fatty acid tails via ester linkages
• phosphodiester linkage to a polar head group
  
  • head group determined behavior and properties
  • can be positive, negative, neutral

Question 4

Sphingolipids

Answer 4

• ex. cell surface antigens on RBC to determine blood type
• sphingosine/sphingoid backbone (OHCHR-CHNH-CH2-OR)
• fatty acid tails and polar heads
• phospholipids - linked via phosphodiester
• glycolipid - linked via glycosidic linkage
• Subclass based on head group -
  
  • ceramide - hydrogen head group
  • sphingomyelins - is a phospholipid, in plasma membrane of oligodendrocytes and Schwann cells. No net charge
  • glycosphingolipids - glycosidic bonds hold together sugar head group. No net charge
    
    • cerebrosides - single sugar
    • globosides - 2 or more sugars
  • Gangliosides - glycolipids, oligosaccharides for head group
    
    • N-acetylneuraminic acid aka sialic acid at terminus
    • negative charge

Question 5

Waxes

Answer 5

• esters of long chain fatty acids with long chain alcohols

Question 6

Terpenes

Answer 6

• lipids from C5H8 aka isoprene
• Products range from 2 - 1000 monomers of C5H8 (isoprene)
  
  • Vitamin A - 4 isoprene units
• Terpenoids - oxidized terpene

Question 7

Steroids

Answer 7

• 4 cycloalkane rings
  
  • 4 cyclohexane and 1 cyclopentane
  • greatly nonpolar
  • testosterone, estrogens, cortisol, aldosterone
• function defined by functional groups and oxidation status
• Cholesterol -
  
  • in phospholipid bilayer, keeps it fluid
  • amphipathic allows it to keep fluidity
  • precursor to hormones, bile acids, Vit D

Question 8

Prostaglandins

Answer 8

• unsaturated carboxylic acids
• arachidonic acid is the derivative, one 5 carbon ring
• regulate cAMP synthesis
• effect smooth muscle, sleep-wake cycle, body temp increase due to pain/fever

Question 9

Fat soluble vitamins

Answer 9

• vitamin - essential and cannot be adequately synthesized by body
• A - carotene - unsaturated hydrocarbon, vision, growth, immune function
  
  • retinal - aldehyde form of Vit A, retinol is storage form
  • retinoic acid - oxidized retinol - regulate gene expression, epithelial development
• D - cholecalciferol - formed in UV light dependent reaction
  
  • converted to calcitriol (bio active form of vit D)
    
    • increase Ca uptake in intestines
  • lack results in rickets
• E - tocopherols and tocotrienols - substituted aromatic ring, long side chain
  
  • antioxidants
• K - phylloquinone and menaquinone
  
  • posttranslational medifications to form prothrombin (clotting)
  • introduces calcium binding sites on proteins

Question 10

Triacylglycerol

Answer 10

• aka triglycerides
• 3 fatty acids bonded via ester linkages to glycerol
• nonpolar and hydrophobic
• adipocytes - large storage of fat
• triglycerols travel between liver and adipose tissue
• characteristics determined by saturation

Question 11

Free fatty acids

Answer 11

• unesterified fatty acids, free carboxylate group
• saponification - ester hydrolysis of triacylglycerols via a strong base (NaOH)
• fatty acid salt is known as soap
• surfactant - lower surface tension of liquid
• colloid - single phase or aqueous and nonpolar liquids
  
  • micelles - aggregates with hydrophobic in and hyrdophilic out. Allows colloids to form
  • help with absorption of fat soluble vitamins