Chapter 23 Lecture Notes - CEM 252 at MSU Spring 1997

Chapter 23 - Lipids

Chapter 23-Slide 1

Chapter 23-Slide 2

Soaps and Detergents

• Soaps are salts of fatty acids
  
• The nonpolar regions cluster in water solutions forming MICELLES
  
• These spherical particles dissolve grease into the non-polar region in the center

Chapter 23-Slide 3

The Importance of Water Solubility

Why are the molecules on the right less soluble?
(write down your reasons)

Chapter 23-Slide 4

Synthetic Detergents - Improved Solubility

• Sulfate salt replaces carboxylate salt
• Why are sulfates more soluble in acidic solutions?

Chapter 23-Slide 5

Fats and Oils: Triacylglycerols

• Fats: solid or semi-solid at room temperature
  
• Oils: liquid at room temperature
  

Chapter 23-Slide 6

Prostaglandins

Functions: lower blood pressure, stimulate smooth muscle contractions, inflammation, ulcer suppression

Chapter 23-Slide 7

Phospholipids

Derived from Glycerol - important membrane components

Chapter 23-Slide 8

Spontaneous Self-Assembly

Phospholipids in water spontaneously assemble into paired layers (bilayers), with hydrocarbon chains in the center and phosphate groups exposed to water

What chemical concepts help explain this?

Chapter 23-Slide 9

The Fluid Mosaic Membrane Model

Membrane components are not covalently connected (a mosaic of pieces)

Membrane components can move around each other in the plane of the membrane

NOTE: Demonstration participants are one layer of the bilayer

Chapter 23-Slide 10

Common Steroids

• Cholesterol (membrane component)
• Androgens (male sex hormones)
  • Testosterone
  • Andosterone
• Estrogens (female sex hormones)
  • Progesterone
  • Estrone
• Corticoid Hormones (metabolic regulators)
  • Cortisone
  • Cortisol
  • Aldosterone

Chapter 23-Slide 11

Cholesterol

Precurser for many hormones, the bile acids, and vitamin D

Rigid structure provides stiffness to cell membranes (~10% of membranes by weight)

Chapter 23-Slide 12

Rigidity of Fused Ring System

Chapter 23-Slide 13

Highlights of Cholesterol Biosynthesis
(Understanding Organic Chemistry is Useful!)

All carbon atoms in cholesterol come from acetyl groups via coenzyme A (CoA)

Isopentenyl pyrophosphate is a key intermediate

What type of conversion is this?

Chapter 23-Slide 14

Building up to Squalene

What properties make this process favorable?

What reaction is this mechanism analgous to?

Chapter 23-Slide 15

Fat-Soluble Vitamins

• Vitamin A - essential in vision
  
• Vitamin D - essential in calcium/phosphorous metabolism
  
• Vitamin E - antioxidant: traps peroxy radicals
  
• Vitamin K - essential in blood clotting
  

Chapter 23-Slide 16

Olestra: Non-caloric Fat Substitute

Potential Negative Dietary Impact: Dissolve fat-soluble vitamins and prevent their absorption

Solution: Saturate olestra with fat-soluble vitamins - those in the food can be absorbed normally

Chapter 23-Slide 17