Chapter 5

Question 1

Membrane Lipids

Answer 1

Components contributing to structure:
1. Amphipathic: hydrophilic heads and hydrophobic tails, allowing formation of bilayers in aqueous solution
2. Fatty Acid Tails: form bulk of phospholipid bilaryer and play predominant structural role

Components contributing to function:
1. Polar head groups: due to constant exposure to exterior environment of phospholipid bilayer (inside/outside of cell)
2. Degree of unsaturation of fatty acid tails (small role)

Question 2

Sphingolipid

Answer 2

Bond between sphingosine backbone and head group determines whether or not a sphingolipid is also a phospholipid
Sphingolipids used in ABO blood typing
If has phosphodiester bond, it’s a phospholipid
Nonphospholipid sphingolipids: glycolipids (glycosidic linkage to sugar)

Types of Sphingolipids:
1. Sphingomyelin
2. Glycosphingolipid
3. Ganglioside

Question 3

Sphingomyelin

Answer 3

Phospholipid
Functional groups: phosphatidylethanolamine/phosphatidylcholine

Question 4

Glycospingolipid

Answer 4

Glycolipid
Functional Groups: Sugar (mono or polysaccharide)

Question 5

Ganglioside

Answer 5

Glycolipid
Functional groups: oligosaccharides and N-acetylneuraminic acid (NANA)

Question 6

Amphipathic Molecule

Answer 6

Placed in nonpolar solvent:
* Opposite of what happens in water (polar solvent)
* Hydrophilic (polar) part of molecules would be inside
* Hydrophobic (nonpolar) part on exterior exposed to solvent

Question 7

Diterpene

Answer 7

Contain four isoprene units
* Each isoprene unit has 5 carbons
* Total of 20 C for backbone

Question 8

Steroid

Answer 8

Defined by structure
* 3 cyclohexane rings and a cyclopentane ring

Question 9

Steroid Hormone

Answer 9

Molecule within steroid class that functions as a hormone
* Has high affinity receptors
* Affects gene expression and metabolism

Question 10

Prostaglandins

Answer 10

Regulate synthesis of cAMP
* cAMP involved in several pathways
* Ex: pathways that drive pain, inflammation, and smooth muscle function
* Synthesis inhibited by NSAIDs
* Paracrine/autocrine signaling molecules NOT endocrine (affect regions close to where produced, not whole body)

Question 11

Fat Soluble Vitamins

Answer 11

1. A (Carotene):
   * As retinal: vision
   * As retinoic acid: epithelial development
2. D (Cholecalciferol):
   * As calcitriol: calcium and phosphate regulation
3. E (Tocopherols):
   * Antiodixants, using aromatic ring
4. K (Phylloquinone and menaquinones)
   * Posttranslational modification of prothrombin, addition of calcium-binding sites on many proteins

Question 12

Energy

Answer 12

Stored as glycogen and triacylglycerols
Triacylglycerols: preferred because Carbons are more reduced, therefore larger amount of energy yield per unit weight
Due to hydrophobic nature, don’t need to carry extra weight from hydration

Question 13

Triacylglycerols

Answer 13

AKA triglycerides
* Composed of glycerol backbone esterified to three fatty acids
* Used for energy storage

Question 14

Saponification

Answer 14

Exter hydrolysis:Ester bonds of triacylglycerols broken to form a glycerol molecule and salts of fatty acids (soap) using a strong base (Na/KOH)

Question 15

Soap

Answer 15

Appears to dissolve in water because amphipathic free fatty acid salts from micelles with hydrophobic fatty acid tails towards center and carboxylate groups facing out toward water
* Fat soluble particles can dissolve inside micelles in soap-water solution and wash away
* Water-soluble compounds can freely dissolve in water

Question 16

Saturation

Answer 16

• Can describe number of double/triple bonds in fatty acid tail
• Determines at least one of the properties of membranes
• Fully saturated fatty acids: have only single bonds and are fless fluid solution (can pack more tightly and form more noncovalent bonds, therefore more energy needed to disrupt structure)

Question 17

Glycerophospholipids

Answer 17

• Subset of phospholipids
• Never sphingolipids because contain glycerol backbone not spingosine/sphingoid
• Have polar head group, glycerol, two fatty acid tails

Question 18

Cholesterol

Answer 18

Steroid hormone precursors with variable effects on membrane fluidity depending on temeprature
* Interacts with hydrophobic tails and hydrophilic heads of membrane lipids
* Precursor for vitamin D (produced in skin in UV driven reaction)