Unit 2 - C. D. E. Phospholipids, Sphingolipids, Steroids Flashcards
Phospholipids
- second largest family of lipids
- two fatty acids + glycerol + phosphate group + alcohol group
Function of Phospholipids
- Component of cell membrane - for signal transmission and anchor for proteins/carbohydrates
- Component of body fluid - (bile, plasma, lung surfactant) to make cholesterol soluble or decrease surface tension
sphingolipid molecular component
Similar to phospholipid/triglyceride but has a sphingosine instead of glycerol as backbone
sphingosine
long-chain unsaturated amino alcohol
ceramide
sphingosine + fatty acid off amine group via amide linkage
sphingomyelin
ceramide + phosphorylcholine group off carbon #1
glycosphingolipids
ceramide + carbohydrate off carbon #1
Include: cerebrosides, globosides, and gangliosides
cerebroside
- a glycosphingolipid
- carbohydrate is glucose or galactose
globoside
- a glycosphingolipid
- 2-4 carbs (glucose, galactose, or N-acetylgalactosamine)
ganglioside
- a glycosphingolipid
- 7 carbs, at least one being NANA (N-acetylneuraminic acid)
Function of Sphingomyelin
- 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
Myelin
- 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
Function of Cerebroside
- Found in myelin sheath (15% of lipid component)
- outer layer of cell membrane - to regulate cellular interactions with extracellular environment
- Galactocerebroside = nerve cell membranes
- Glucocerebroside = non-neural cell membranes
Lactosylceramide
- a globoside
- contains glucose and galactose
- component in RBC membrane
Function of Sphingolipids (general)
- component of cell membranes (esp. nerve cells)
- have a greater resistance of hydrolysis than phospholipids because amide linkage is stronger than ester linkage
Function of Gangliosides
- Bind to viruses and bacteria toxins
- Form complexes with amyloid beta (protein) that forms aggregates
- Promotes tumor associated angiogenesis and enhances proliferation and metastasis of tumor cells
Steriods
- nonsaponifable esters (do not hydrolyze w. base)
- not found in bacteria
- free or esterified to F.A.
General structure of steriod
- 4 fused rings w. 17 carbon atoms
- 3 six membered rings, 1 five membered ring
- rings labeled A-D
Sterol
- subgroup of steroids
- one or more -OH group, double bond in B ring
- found widely in nature in plants, animals, yeast
Stanols
- 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
Cholesterol
- 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
Cholesterol Methods
- Cholesterol ester + H20 -(cholesteryl ester hyrdolase)-> cholesterol + F.A.
- Cholesterol + O2 -(cholesterol oxidase)-> cholest-4-en-3-one +H2O2
- H2O2 +phenol +4-aminoantipyrine -(peroxidase)-> quinoeimine dye + 2 H2O [color change]
Function of phytosterols
- 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
Bile Salts
- 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
Enterohepatic circulation
- 95% bile salts recycled from liver to intestines and back
- Albumin = polar carrier protein to help return bile salts/acid back to intestines
Function of cortisol
- Increase production of glucose in liver (GNG)
- Promote glucogenesis (Both glucogenesis and GNG act to conserve glucose for future energy needs)
- Trigger release of pro-inflammatory (small amounts of cortisol) and anti-inflammatory cytokines (large amounts)
- Adverse side effects if used therapeutically for too long
Measuring Cortisol
- Free cortisol (lab send out)
- total cortisol (measure free and bound)
- both use immunoassays
- Cortisol levels change throughout the day
Function of Renin-angiotensin-aldosterone
- 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
