Unit 2 - C. D. E. Phospholipids, Sphingolipids, Steroids

Question 1

Phospholipids

Answer 1

• second largest family of lipids

- two fatty acids + glycerol + phosphate group + alcohol group

Question 2

Function of Phospholipids

Answer 2

1. Component of cell membrane - for signal transmission and anchor for proteins/carbohydrates
2. Component of body fluid - (bile, plasma, lung surfactant) to make cholesterol soluble or decrease surface tension

Question 3

sphingolipid molecular component

Answer 3

Similar to phospholipid/triglyceride but has a sphingosine instead of glycerol as backbone

Question 4

sphingosine

Answer 4

long-chain unsaturated amino alcohol

Question 5

ceramide

Answer 5

sphingosine + fatty acid off amine group via amide linkage

Question 6

sphingomyelin

Answer 6

ceramide + phosphorylcholine group off carbon #1

Question 7

glycosphingolipids

Answer 7

ceramide + carbohydrate off carbon #1

Include: cerebrosides, globosides, and gangliosides

Question 8

cerebroside

Answer 8

• a glycosphingolipid

- carbohydrate is glucose or galactose

Question 9

globoside

Answer 9

• a glycosphingolipid

- 2-4 carbs (glucose, galactose, or N-acetylgalactosamine)

Question 10

ganglioside

Answer 10

• a glycosphingolipid

- 7 carbs, at least one being NANA (N-acetylneuraminic acid)

Question 11

Function of Sphingomyelin

Answer 11

• contain dual polarity
  1. found in gray matter (stearic/palmitic fatty acids)
  2. found in myelin sheath to insulate and protect axons (lignoceric/nervonic fatty acids) - loss = multiple sclerosis

Question 12

Myelin

Answer 12

• dielectric (electrically insulating) material around axon of neuron
• fat helps insulate axons from electrically changed atoms/molecules
• 40% water, Dry splits 70% lipids & 30% protein
• proteins = myelin basic protein, myeline oligodendrocyte glycoprotein, and proteolipid protein
• primary lipid = glycoside galactocerebroside
• strength from intertwining hydrocarbon chains of sphingomyelin

Question 13

Function of Cerebroside

Answer 13

1. Found in myelin sheath (15% of lipid component)
2. outer layer of cell membrane - to regulate cellular interactions with extracellular environment

• Galactocerebroside = nerve cell membranes
• Glucocerebroside = non-neural cell membranes

Question 14

Lactosylceramide

Answer 14

• a globoside
• contains glucose and galactose
• component in RBC membrane

Question 15

Function of Sphingolipids (general)

Answer 15

• component of cell membranes (esp. nerve cells)

- have a greater resistance of hydrolysis than phospholipids because amide linkage is stronger than ester linkage

Question 16

Function of Gangliosides

Answer 16

1. Bind to viruses and bacteria toxins
2. Form complexes with amyloid beta (protein) that forms aggregates
3. Promotes tumor associated angiogenesis and enhances proliferation and metastasis of tumor cells

Question 17

Steriods

Answer 17

• nonsaponifable esters (do not hydrolyze w. base)
• not found in bacteria
• free or esterified to F.A.

Question 18

General structure of steriod

Answer 18

• 4 fused rings w. 17 carbon atoms
• 3 six membered rings, 1 five membered ring
• rings labeled A-D

Question 19

Sterol

Answer 19

• subgroup of steroids
• one or more -OH group, double bond in B ring
• found widely in nature in plants, animals, yeast

Question 20

Stanols

Answer 20

• subgroup of steroids
• similar to sterol but without the double bond (one or more -OH group)
• also found widely in nature in plants, animals, yeast

Question 21

Cholesterol

Answer 21

• most abundant sterol
• constituted cell membranes, nuclear membranes, golgi apparati, and mitochondria
• mainly non-polar= insoluble in water
• precursor for other steriods
• Biosynthesis starts with acetyl CoA mostly in the liver
• 50% excreted, 50% reabsorbed
• high cholesterol can cause atherosclerosis and stroke

Question 22

Cholesterol Methods

Answer 22

1. Cholesterol ester + H20 -(cholesteryl ester hyrdolase)-> cholesterol + F.A.
2. Cholesterol + O2 -(cholesterol oxidase)-> cholest-4-en-3-one +H2O2
3. H2O2 +phenol +4-aminoantipyrine -(peroxidase)-> quinoeimine dye + 2 H2O [color change]

Question 23

Function of phytosterols

Answer 23

• sterols/stanols derived from plants
  1. Lower serum cholesterol levels (because it is very similar in structure to cholesterol = competition)
  2. Lowers LDL (“Bad”) cholesterol due to increase production of LDL -receptors because less cholesterol is being absorbed

Question 24

Bile Salts

Answer 24

• bile acid + glycerine/taurine -> bile salt (in liver)
• bile = bile salts + bile pigments + water + F.A. + lecithin + cholesterol. It is stored in the gallbladder and secreted to intestines
• emulsifying agents = increase surface area of lipid helps lipase in digestion

Question 25

Enterohepatic circulation

Answer 25

• 95% bile salts recycled from liver to intestines and back

- Albumin = polar carrier protein to help return bile salts/acid back to intestines

Question 26

Function of cortisol

Answer 26

1. Increase production of glucose in liver (GNG)
2. Promote glucogenesis (Both glucogenesis and GNG act to conserve glucose for future energy needs)
3. Trigger release of pro-inflammatory (small amounts of cortisol) and anti-inflammatory cytokines (large amounts)
4. Adverse side effects if used therapeutically for too long

Question 27

Measuring Cortisol

Answer 27

• Free cortisol (lab send out)
• total cortisol (measure free and bound)
• both use immunoassays
• Cortisol levels change throughout the day

Question 28

Function of Renin-angiotensin-aldosterone

Answer 28

• cleaves angiotensinogen -> angiostensin I that inturn converts to -> angiotensin II that causes:
  1. secretion of aldosterone = Sodium and Water retention
  2. secretion of ADH (vasopressin) = Water reabsorption
  3. stimulates hypothalamus to activate thirst reflex