Lipids

Question 1

Define amphipathic molecule

Answer 1

• Molecule that has both hydrophilic and hydrophobic regions.
• Example: Phospholipid has hydrophilic polar head and hydrophobic fatty acid tails.

Question 2

Steroid

Answer 2

• Metabolic derivative of squalene (type of terpene).
• Structure made up of three cyclohexane rings and one cyclopentane ring.
• Nonpolar.

Question 3

Fat-Soluble Vitamins

Answer 3

• Vitamin A (carotene, vision).
• Vitamin D (can be consumed or formed in UV light-driven reaction in skin, absorption of calcium).
• Vitamin E (antioxidant).
• Vitamin K (important in coagulation).
• A, D, E, K.

Question 4

Water-Soluble Vitamins

Answer 4

• B, C.

Question 5

Cholesterol

Answer 5

• Amphipathic steroid found in phospholipid bilayer, responsible for maintaining membrane fluidity.
• At low temperatures, it keeps cell membrane from solidifying, this increasing fluidity; at high temperatures, it holds membrane intact and prevents it from becoming too permeable, thus decreasing fluidity.

Question 6

Triacylglycerols (Triglycerides)

Answer 6

• Used for energy storage.
• Carbon atoms of fatty acids are more reduced than those of sugars, yielding twice the amount of energy per gram upon oxidation.
• Triacylglycerols are hydrophobic; they do not draw in water and do not require hydration for stability, decreasing their weight and increasing their energy density (in comparison to hydrophilic polysaccharides).