Lipids

Question 1

Primarily hydrocarbon chains and rings (few functional groups) are important in lipids because….

Answer 1

Strongly hydrophobic – useful for waterproofing (cells, leaves, fur and feathers)

Question 2

Many C-C and C-H bonds are useful for lipids because….

Answer 2

High potential energy when oxidized – good low mass storage molecule

Question 3

Low electrical conductivity is useful for lipids because….

Answer 3

Good insulator for nerves (myelin sheaths)

Question 4

Slow to heat and cool is useful for lipids because….

Answer 4

Provides good thermal insulation – subcutaneous fats in whales, seals, waterbirds, humans

Question 5

Identify 4 categories of lipids

Answer 5

1. Triglyceride (or triacylglycerol) = fats & oils
2. Steroids
3. Waxes
4. Phospholipids

Question 6

What are the properties of a saturated triglyceride? + give an everyday example

Answer 6

Saturated fats have no double bonds in the hydrocarbon chains of their fatty acids. Stearic acid, found in most mammals and palmitic acid (found in palm oils) are saturated.

Question 7

What are the properties of an unsaturated triglyceride? + give an everyday example

Answer 7

Monounsaturated fatty acids have one double bond, while polyunsaturated fatty acids have two double bonds. Oleic acid, found in olive oil, is monounsaturated. Linoleic and linolenic acids, found flax seed oil, and most fish oils are polyunsaturated.

Question 8

Ester Bond

Answer 8

O
||
- C - O - C

Question 9

Why are trigycerides considered macromolecules but not technically polymers?

Answer 9

While polymers can be extended ad infintum with the addition of more monomers, fats have only three fatty acid residues.

Question 10

What are the properties of a phospholipid?

Answer 10

Phospholipids are primarily made from triglycerides but one fatty acid is replaced by a phosphate that in turn is usually attached to a small hydrophilic molecule. The hydrophilic “head” orients away from the hydrophobic tails and produces an amphiphilic molecule.

Question 11

Review how phospholipids form a stable bilayer in water.

Answer 11

Phospholipids can form a stable bilayer in water with the heads of both layers oriented outward and the hydrophobic tails sandwiched in a water-free layer between them. Such bilayers always separate an inner watery environment (cytoplasm) from and outer watery environment

Question 12

What is a steroid? What molecule are all other steroids derived from?

Answer 12

A lipid soluble hormone derived from cholesterol.

Question 13

What functions do steroids play in living things?

Answer 13

Cholesterol is an important constituent of animal cell membranes, giving them strength and viscosity that helps to compensate for the lack of a cell wall and making them more resistant to solidifying when cooled. Steroids are hormones derived from cholesterol that play important roles in maturation, sexual function, stress, mineral balance (especially sodium) and, in other animals, molting and metamorphosis.

Question 14

Basic Structure of a Steroid

Answer 14

Bunch of hexagons thrown together….