Lipids

Water insoluble (hydrophobic)

Non-polymeric structure

Energy storage, membrane constituent, hormone signaling

Migrate over-water 2,400 miles

I. Fatty Acids: Fuel & Membrane Building BlocksHydrocarbon with carboxylic acid head group

Highly reduced carbon source

Ionized at neutral pH (-ate not -ic acid form)

Which fatty acid is more reduced?

What makes soap a good cleaner?

Soap: fatty acid salt Soap: fatty acid salt

Naturally Occurring Animal Fatty Acids: Common and Systemic Names

Melting Point and Membrane Fluidity

Shorter chain length lowers melting point

cis Double bond lowers melting point

Unsaturated fatty acids (oils) lower melting point versus saturated fatty acids (solid)

Predict the oil composition from palm versus canola plants.

Health Versus Fat Quantity and Quality

Trans fats correlated with high blood cholesterol/cardiovascular disease (inflammation?)

Cis polyunsaturated fatty acids essential for the diet (inhibit blood clotting, reduce heart attack risk)

Vegetable oil (linolenate)

Shell fish/cold water fish (EPA/DHA)

II. Triacylglycerol in Energy StorageAnhydrous fat /gram stores 6x energy of hydrated glycogen

Triacylglycerol storage site – adipose tissue

Sugar storage 18 hrs; triacylglycerol storage several weeks

III. Phospholipids: Major Class of Membrane Lipids

Phosphatidate: key intermediate in phosphoglyceride biosynthesis and membranes

Lipid bilayer

Common Membrane Phosphoglycerides

What does the color coding for green, blue and pink represent?

Membrane Sphingolipids

Amino alcohol backbone – sphingosine

Sphingomyelin –sphingosine with a fatty acid amide linkage and choline; abundant in nerve cell membranes

Cerebroside – sphingosine with a sugar residue (aka glycolipid)

IV. Glycolipids

Gangliosides – sphingosine with multiple sugar residues

Sugars are extracellular

A, B and O blood typing

Multiple sugar units

V. Steroids

How does cholesterol orientate in the membrane?

Tetracyclic ring structure (3 cyclohexane fused with cyclopentane)

Facilitate lipid digestion

Membrane fluidity buffer

LipoproteinsProtein attachment to the surface of a membrane

N-Myristoylglycine

Membrane Component from a High-Temperature Organism

What are the chemical differences in this lipid from standard membrane lipids?

What impact do these alterations have on lipid behavior?

Phospholipids and Glycolipids Self-Assemble to Form a Lipid Bilayer

Driving Forces:

• H-bonding

• Hydrophobic effect

• Electrostatic interactions

• Van der Waal’s attractions (close packing)

Membrane Fluidity: Temperature, Cholesterol and Fatty-Acid-Composition Regulated

How does membrane composition alter with elevated temperature?

Significant Lateral Albeit Minimal Transverse Lipid Movement

Liposome for Potential Drug Delivery

Lipid Bilayer Small-Molecule Permeability

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* * *

Unassisted membrane crossing linked with H2O and non-polar solvent solubility

* Protein assisted transport

Peripheral and Integral Membrane Proteins

What tethers peripheral proteins to the membrane?

What secondary structure is common in membrane hydrophobic regions?

Different membrane orientation (a and e), surface position (f and e) and membrane componentassociation (d, and g)

Alpha Helices in the Integral Protein Bacteriorhodopsin

Bacteria light-harvesting protein that generates proton gradient

α-Helix most common 2° membrane structure

Helical (yellow) and charged (red) residues

Chapter 8 Problems: 1, 3, 5, 7, 9, 19, 21, 23 and 25