Download Biochemistry: A Short Course

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 Blocks
Hydrocarbon with carboxylic acid head group
Soap: fatty acid salt
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?
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 Storage
Anhydrous 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
Tetracyclic ring structure
(3 cyclohexane fused with
cyclopentane)
Facilitate lipid digestion
Membrane fluidity buffer
How does cholesterol
orientate in the
membrane?
Lipoproteins
Protein attachment to the surface of a membrane
N-Myristoylglycine
Membrane Component from a HighTemperature 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 SelfAssemble 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-AcidComposition 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
Unassisted membrane
crossing linked with
H2O and non-polar
solvent solubility
* Protein assisted transport
*
*
*
*
*
Peripheral and Integral Membrane Proteins
Different membrane orientation
(a and e), surface position
(f and e) and
membrane
component
association
(d, and g)
What tethers peripheral proteins to the membrane?
What secondary structure is common in membrane
hydrophobic regions?
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