Lecture 13: Storage Lipids

Chapter 10.1

What are fatty acids?

carboxylic acids with hydrocarbon chains ranging from 4 to 36 carbons long

True or False: The oxidation of fatty acids (to CO₂ and H₂O) is highly exergonic.

true

Why do fats contain the highest calorie per unit?

fats are very reduced

Fatty acids can be what?

• can be saturated or unsaturated

• can be branched or unbranched

What are saturated fatty acids?

fatty acids with only single carbon-carbon bonds

What are unsaturated fatty acids?

fatty acids containing 1 or more carbon-carbon double bonds

What is the nomenclature for unbranched fatty acids?

1. separate the chain length and number of double bonds with a colon

2. begin numbering at the carboxyl carbon

3. indicate the positions of the double bonds by a delta and a superscript number

4. designate whether the double bond is cis or trans

What are the 3 ways to name fats?

• number of carbons

• greek letters

• omega

PUFAs contain more than what in their backbone?

more than one double bond

What are omega-3 fatty acids?

fatty acids with a double bond between C-3 and C-4 relative to the most distant carbon

What are omega-6 fatty acids?

fatty acids with a double bond between C-6 and C-7 relative to the most distant carbon

Which omega-3 PUFA must humans obtain from their diet?

a-linolenic acid

True or False: The human body can convert a-linolenic acid to other PUFAs.

true

Which foods are rich in omega-3s?

seafoods and vegetables

What do humans use a-linolenic (ALA) to synthesize?

eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)

What does the extent of packing depend on?

fatty acid saturation

At room temperature, what states are saturated and unsaturated fatty acids in?

• saturated fatty acids are solids

• unsaturated fatty acids are liquids

Triacylglycerols are also called what?

fats or triglycerides

What are triglycerides composed of?

composed of three fatty acids, each in an ester linkage with a single glycerol

What are simple and complex triglycerides?

simple triglycerides contain one kind of fatty acids and mixed triglycerides contain two or three different fatty acids

True or False: Triglycerides are non-polar/hydrophobic—meaning they are essentially insoluble in water.

true

How many hydroxyl groups does glycerol contain?

3 hydroxyl groups

 How vertebrates and plants store triglycerides?

• vertebrates store fats as lipid droplets in adipocytes

• plants store fats in the seed

What enzyme do adipocytes and germinating seeds contain?

lipases

What do lipases do?

lipases catalyze the hydrolysis of triacylglycerol—releasing fatty acids for export

True or False: 95% of adipocytes are filled with lipids.

true

What are some functions of waxes?

energy storage and water repellants

What do biological waxes consist of?

esters of long-chain (C₁₄ to C₃₆) saturated and unsaturated fatty acids with long-chain (C₁₆ to C₃₀) alcohols

What is important to know about waxes?

• higher melting point compared to triacylglycerols

• water-repellant properties

• firm consistency