Complex LipidsSections 13.4-13.8By: Cassie Webb and Alyssa Keifer

13.4 What are the Structures of Complex Lipids? Main components of membranes Classified into two groups Phospholipids

Contain an alcohol, 2 fatty acids, and a phosphate group

Two types Glycerophospholipids and sphingolipids

Glycolipids Complex lipids contain carbohydrates

13.5 What Role Do Lipids Play in the Structure of Membranes? Complex lipids form membranes around

body cells and small structures inside the cells (organelles)

Unsaturated Fatty Acids Lipid molecules in bilayer contain at

least one Prevent tight packing of hydrophobic

chains Provides a liquid-like character to

membranes Similar effect causes lower melting points

than saturated

Membranes Separate cells from external environment

and provide the transportation for nutrients and waste products into and out of the cells

Made of lipid bilayers Two layers of complex lipid molecules

arranged tail to tail Hydrophobic

Get as far from water as possible Hydrophilic

On the surface

Membranes cont. Lipid part acts as barrier against

movement of ions or polar compounds in or out.

Protein molecules located on the surface, partly, or fully in the bilayer Polar compounds transported through

protein channels or active transport.

Fluid Mosaic Model Allows the passage of nonpolar

compounds by diffusion Mosaic: meaning topography of bilayers Fluid: meaning free lateral motion in

bilayers making it liquid-like

13.6 What are Glycerophospholipids? Structure similar to fats Membrane components of cells

throughout the body Alcohol in it is glycerol

Glycerophospholipids Composed of 2 of 3 groups are esterified fatty acids

May be any long-chain carboxylic acids with or without double bonds

3rd group is esterified by a phosphate group Esterified to another alcohol

Letchin Another name A major component of egg yolk Both polar and nonpolar portions in one

molecule good emulsifier

Example: mayonnaise Cephalins

Similar to letchins Contain different alcohols

PI (phosphatidylinositol) The alcohol inositol is bonded to rest of

the molecule by phosphate ester bond Fundamental structural parts of

membrane In the form of PIP2 serves as a signaling

molecule in chemical communication

13.7 What are Sphingolipids? They were discovered in 1874 by Johann

Thudichum Named after a monster from Greek

mythology the sphinx A creature who devoured all who could

not provide the correct answers to the riddles.

Properties Alcohol sphingosine

A long-chain fatty acid connected to NH₂ Ceramide

A combination of a fatty acid and a sphingosine

They may use different fatty acids

Sphingomyelins They are the most important lipids in

the myelin sheaths of the nerve cells. Associated with diseases

Example: multiple sclerosis

13.8 What are Glycolipids? Complex lipids that contain carbohydrates

and ceramides Cerebrosides are one group

They contain a ceramide mono- or oligosaccharide

Occur primarily in the brain and nerve synapses

Gangliosides are another group Have a more complex carbohydrate structure