5.3 Energy Storage

Question 1

Triacylglycerols

Answer 1

• class of lipids specifically used for energy storage
• composed of three fatty acids
  bonded by ester linkages to glycerol; it is rare for all three fatty acids to be the same
• these compounds are nonpolar and hydrophobic
• deposits can be observed in cells as oily droplets in the cytosol
• serve as depots of metabolic fuel
• travel bidirectionally in the bloodstream between the liver and adipose tissue
• hydrolyzed by naturally occurring bases

Question 2

Why are lipids a great way to store energy?

Answer 2

• 1st: the carbon atoms of fatty
  acids are more reduced than those of sugars, which contain numerous alcohol groups; once triacyglycerols are oxidized yields twice the amount of energy per gram as carbohydrates, making this a far more energy-dense storage mechanism compared to polysaccharides like glycogen
• triacylglycerols are hydrophobic. They do not draw in water and do not require hydration for stability. This helps decrease their
  weight, especially in comparison to hydrophilic polysaccharides

Question 3

What’re the two main methods of energy storage in the body?

Answer 3

• triacylglycerols in adipose
  tissue or as carbohydrates in glycogen
• Glycogen is faster and water-soluble and because of its low energy density, glycogen can only provide energy for a bit less than one day
• Carbs. take longer to mobilize

Question 4

How are physical characteristics of triacylglycerols determined?

Answer 4

• the saturation (or unsaturation) of the fatty acid chains that make them up, much like phospholipids

Question 5

Free fatty acids

Answer 5

• unesterified fatty acids with a free carboxylate group
• these circulate in the blood bonded noncovalently to serum
  albumin

Question 6

Saponification

Answer 6

• the ester hydrolysis of triacylglycerols using a strong base (lye)
• Lye is KOH or NaOH
• result is the basic cleavage of the fatty acid, leaving the sodium salt of the fatty acid and glycerol
  *fatty acid salt is soap

Question 7

Surfactant

Answer 7

• lowers the surface tension at the surface of a liquid, serving as a detergent or emulsifier
• Soaps can act as surfactants

Question 8

Colloid

Answer 8

• a mixture is two or more substances mixed together but not chemically combined ( they can be separated ). They are a special type of mixture where tiny particles of one substance are scattered through another substance
• created by soaps
• Occurs b/c of micelles

Question 9

Micelles

Answer 9

• important in the body for the absorption of fat-soluble
  vitamins (A, D, E, and K) and complicated lipids such as lecithins.
• Fatty acids and bile salts secreted by the gallbladder form micelles that can
  increase the surface area available for lipolytic enzymes

Question 10

How do cleaning agents dissolve both watersoluble
and water-insoluble messes?

Answer 10

• Nonpolar compounds can dissolve in the hydrophobic interior of the watersoluble
  micelle