Lipids

Question 1

Roles for lipids in organisms

Answer 1

• Energy Storage (fats/oils)
• Cell Membranes (phospholipids)
• Capture of light energy (carotenoids)
• Hormones and vitamins (steroids/modified fatty acids)
• Thermal insulation
• Electrical insulation of nerves
• Water repellency (waxes/oils)

Question 2

How do fats form?

Answer 2

Dehydration reactions (condensation reactions)

Question 3

Structure of fats

Answer 3

• consist of glycerol linked by ester linkages to three fatty acids

Question 4

Structure of phospholipids (phosphatidylcholine)

Answer 4

Hydrophilic head:
- Choline
- Phosphate
Hydrophobic tail:
- Glycerol
- Hydrocarbon chains

• Makes up cell membrane

Question 5

Describe the phospholipid bilayer

Answer 5

• hydrophilic heads interact with water
• hydrophobic tails interact with one another
• phospholipids are in constant lateral motion, but rarely flip to the other side of the bilayer

Question 6

Describe the effects of double bonds in phospholipids

Answer 6

• causes a kink in the phospholipid’s tail

- increases permeability of cell membrane, letting through more fluid

Question 7

Describe saturated lipids

Answer 7

• are linear, are bonded to the maximum number of hydrogens, and are solids at room temp
• Ex: Butter, Beeswax

Question 8

Describe unsaturated lipids

Answer 8

• have kinks in its structure (non-linear), have double/triple bonds, and are liquids at room temp
• Ex: Vegetable oil

Question 9

What does it mean when a protein is amphipathic? Why are these important?

Answer 9

• means to have both hydrophilic (polar and charged amino acids) and hydrophobic (nonpolar amino acids) parts
• these proteins can integrate into lipid bilayers

Question 10

List molecule types in increasing permeability of the phospholipid bilaer

Answer 10

ions < large, uncharged polar molecules < small, uncharged polar molecules < small, nonpolar molecules