lipids

Question 1

what do all lipids have in common with respect to solubility

Answer 1

• they all have low solubility in aqueous solutions

Question 2

what does 20:2 (Δ^8,11) mean when describing a fatty acid?

Answer 2

• there are 20 saturated carbons and 2 unsaturated carbons
• carbons 8 and 11 are the start of the double bond

Question 3

how do hydrocarbon chain length and saturation affect the melting point of fatty acids? How do these affect the tightness of packing between fatty acids into aggregates?

Answer 3

1. longer chain and higher saturation = higher melting point, lower solubility
2. longer chain = tighter packing because more interactions
3. unsaturated fatty acids have more kinks, which reduces tightness of packing

Question 4

for unsaturated fatty acids, is the conformation around the double bond usually cis or trans?

Answer 4

• almost always cis

Question 5

what is the basic structure of a triglyceride

Answer 5

• three fatty acids with ester linkage to a glycerol
• can have the same or different types of fatty acids
• can be saturated, unsaturated, or combo

Question 6

what is more soluble, a fatty acids, or triglyceride? why?

Answer 6

• carboxylic acids are more polar than the OH groups on a glycerol
• polarity from carboxylic acids lost in ester bonds to the glycerol

Question 7

what fuel storage lipid is contained in adipocyte cells?

Answer 7

• triacylglycerols
• form oily droplets int he cytoplasm of eukaryotic cells
• adipocytes store fat droplets that nearly fill the cell

Question 8

why are fats better for long-term storage of energy compared to carbohydrates?

Answer 8

• carry more energy because theyre more reduced
• they are hydrophobic and therefore unhydrated, so the organism doesn’t have to carry water weight to store it

Question 9

how do sphingolipids and glycerolipids differ?

Answer 9

• sphingolipids have an amide linkage to fatty acid, glycerolipids are ether-linked
• glycerol backbone vs sphingosine backbone
• triglycerides are a type of glycerolipids

Question 10

what are three major parts of the cholesterol molecule?

Answer 10

1. polar head group
2. steroid nucleus (four connected rings)
3. alkyl side chain

Question 11

structurally, how are steroid hormones different from cholesterol?

Answer 11

• ## steroids lack the hydrocarbon chain (more polar)