Ch 11: Lipids

What is a lipid?

Large heterogeneous and water-insoluble molecules

What are lipids soluble in?

Organic solvents

Lipids store energy that fuels what?

Metabolic pathways

What are lipids a key component of?

Membranes

What are the classes of water insoluble lipids?

Free fatty acids, triacylglycerols/triglycerides, and biological wax

What are the classes of amphipathic lipids?

Phospholipids, glycolipids, and steroids

What is a fatty acid?

A hydrocarbon chain that terminate with carboxylic acid groups

Saturated fatty acid

Fatty acids composed of only single bonds

Unsaturated fatty acids

Fatty acids composed of only double and triple bonds

Monounsaturated fatty acids (MUFAs)

Unsaturated fatty acids with one double bond

Polyunsaturated fatty acids (PUFAs)

Unsaturated fatty acids with two or more double bonds

Systematic name of C₁₈ saturated fatty acid

Octadecanoic acid

Common name of C₁₈ saturated fatty acid

Stearic acid

What is the numerical shorthand notation for fatty acids?

Number of carbon atoms: Number of double bonds

16:0 fatty acid

Saturated fatty acid with 16 carbons and no double bonds

18:1

Monosaturated fatty acid with 18 carbons and 1 double bond

Why do unsaturated fatty acids have lower melting points of saturated fatty acids of the same length?

Cis double bond introduces a kink in the fatty acid, making tight packing between the chains impossible, which limits the van der Waals interactions between the chains.

What properties change when a double bond is introduced in a fatty acid?

Melting point is lowered, packing efficiency lowers, membrane fluidity increases

Triacylglyceride structure

One glycerol and three fatty acids linked by esterification

Why are fatty acids so much more energy rich?

1. Store more energy than carbs

2. Triacylglycerols are hydrophobic and store as nearly anhydrous

Where is most triacylglycerol accumulated in mammals?

Adipose tissue

Where is adipose tissue distributed in mammals?

Under the skin and throughout the body

What is adipose tissue synthesized for?

1. Synthesis and storage of triacyclglycerols

2. Mobilization into fuel molecules to be transported into other tissues via the bloodstream

3. Thermal insulators to help maintain body temp

What is triacylglycerol broken down into with the help of 3 NaOH?

Glycerol and soap

Biological waxes

Long-chains if saturated and unsaturated fatty acids attached to long chain alcohols

How long is the fatty acid chain in biological waxes?

14-36 carbons

How long is the alcohol chain in biological waxes

16-30 carbons

What is the function of biological waxes in species?

Protect leaves, feathers, hair, skin

Phospholipid components

1. One or more fatty acids

2. Scaffold or platform that fatty acids attach to

3. Phosphate group

4. Alcohol attached to the phosphate

What are the two types of scaffolds?

1. Glycerol

2. Sphingosine

Phosphoglyceride structure

• 2 fatty acids

• backbone

• phosphate

• alcohol

Sphingolipid structure

• 1 fatty acid

• backbone

• phosphate

• alcohol

Importance of sphingolipids

Role in formation of lipid rafts

Sphingosine

Amino alcohol with a long, unsaturated chain

Sphingomyelin

Common in membranes, rich in myelin sheath of nerve cells

Glycolipids

Sugar-containing lipids that have a large role in cell-cell interactions

What are glycolipids in animal cells derived from?

Sphingosine

In what fashion of orientation are glycolipids in membranes?

Asymmetric

Major phosphoglycerides

• Ethanolamine

• Choline

• Glycerol

• Inositol

• Serine

What is the function of steroids?

Powerful hormones that facilitate digestion

What structure do steroids exhibit?

Cyclical

What is the most common steroid?

Cholesterol

Importance of cholesterol?

Maintaining membrane fluidity

Lipid membranes are

Amphipathic molecules

What part of the lipids are hydrophobic?

The tails

What part of the lipids are hydrophilic

The head

Eicosanoid hormones

Special class of signaling hormones

Eicosanoid hormones are precursors to what major classes of signaling molecules?

1. Prostaglandins

2. Prostacyclins

3. Thromboxanes

4. Leukotrienes

What do hydrophobic moieties facilitate?

Membrane association