Biochemistry Chapter 5: Lipid Structure and Function

Question 1

Are lipids soluble in water? nonpolar organic solvents?

Answer 1

Water - no

Nonpolar organic solvents - yes

Question 2

What does it mean to be amphipathic?

Answer 2

Both polar and nonpolar

Question 3

What are lipids composed of?

Answer 3

hydrophilic (polar) head group and a nonpolar hydrophobic tail

Question 4

How is the head group attached?

Answer 4

Via a phosphodiester linkage

Question 5

What determines the fluidity of the membrane?

Answer 5

saturation – saturated are less fluid than unsaturated.

Question 6

What are sphingolipids?

Answer 6

contain a sphingosine backbone – many are also phospholipids - called sphingophospholipids.

Question 7

What are sphingomyelins?

Answer 7

Major class of sphingolipids and contain a phosphatidycholine or phosphatidylethanolamine head group – main component of the myelin sheath.

Question 8

What are glycosphingolipids?

Answer 8

Attached to sugar moieties instead of a phosphate group. Cerebrosides have one sugar connected to sphingosine.

Question 9

What is a cerebrosides?

Answer 9

have one sugar connected to sphingosine

Question 10

What are globosides?

Answer 10

Have two or more sugars connected to sphingosine

Question 11

What are gangliosides?

Answer 11

contain oligosaccharides with at least one terminal N-acetylneuraminic acid (NANA); also called sialic acid

Question 12

What are waxes?

Answer 12

contain long-chain fatty acids esterified to long-chain alcohols. They are used as protection against evaporation and parasites in plants and animals.

Question 13

What are terpenes?

Answer 13

Odiferous steroid precursors made from isoprene; a 5-C molecule. 1 terpene unit = 2 isoprene units)

Question 14

What are terpenoids?

Answer 14

derived from terpenes via oxygenation or backbone rearrangement.

Question 15

Steroids

Answer 15

Contain 3 cyclohexane rings and one cyclopentane ring. Their oxidation state and functional groups may vary.

Question 16

What are steroid hormone characteristics?

Answer 16

• high-affinity receptors
• work at low concentrations
• affect gene expression and metabolism

Question 17

What is cholesterol?

Answer 17

important to membrane stability and fluidity; serves as a precursor to a host of other molecules.

Question 18

What are prostaglandins?

Answer 18

autocrine and paracrine hormones that regulate cAMP levels. They have powerful effects on muscle contraction, body temperature and sleep-wake cycle and pain.

Question 19

What are fat-soluble vitamins?

Answer 19

A, D, E, K

Question 20

What is vitamin A for?

Answer 20

aka carotene

metabolized to retinal for vision and retinoic acid for gene expression in epithelial development

Question 21

What is vitamin D for?

Answer 21

aka cholecalciferol
metabolized to calcitriol in the kidneys and regulates calcium and phosphorus homeostasis in the intestines (increasing calcium and phosphate absorption) promoting bone formation.

Question 22

What is vitamin E for?

Answer 22

aka tocopherols

acts as biological antioxidants – their aromatic rings destroy free radicals, preventing oxidative damage.

Question 23

What is vitamin K for?

Answer 23

aka phylloquinone and menaquinones
helps with formation of prothombin, a clotting factor. It performs posttranslational modifications on a number of proteins

Question 24

What are triacylglycerides?

Answer 24

Preferred method of storing energy for long term use. They contain one glycerol attached to three fatty acids by ester bonds.

Question 25

Why do lipids have so much energy?

Answer 25

The carbon atoms are more reduced than in carbohydrates

Question 26

Why are they easier to store?

Answer 26

Triacylglycerols are very hydrophobic, so they are not hydrated by body water and do not carry additional water weight.

Question 27

What are adipocytes?

Answer 27

cells specifically used for storage of large triacylglycerol deposits

Question 28

Saponification

Answer 28

the ester hydrolysis of triacylglycerols using a strong base, like sodium or potassium hydroxide

Question 29

Micelle

Answer 29

can dissolve a lipid-soluble molecule in its fatty acid core and washes away with water because of its shell of carboxylate head groups