Lipids And Membranes Flashcards
The major lipid component of most cellular membranes is…
A) triacylglycerol
B) cholesterol
C)glycerophospholipid
D)cerebrosides
E)gangliosides
C)glycerophospholipid
Which of the following lipid types are derived from fatty acids?
A) triacylcglyerols
B) prostaglandins
C)thromboxanes
D)phospholipids
E) all of the above
E) all of the above
What is the correct abbreviation for the fatty acid shown below?
A)22:5 (5,8,11,14,17)
B)22:4 (5,8,11,14)
C)20:5 (3,6,9,12,15)
D) 20:4 (6,9,12,15)
E) 20:4 (5,8,11,14)
E) 20:4 (5,8,11,14)
Single a yo chain lipids that can act as detergents are most likely to form what type of structure in aqueous solution?
A) vesicles
B) droplets
C) micelles
D)monolayers
E)bilayers
C) micelles
Describe the general properties and some of the functional roles of the major classes of lipids (fatty acids, triacylglycerols, phospholipids, steroids, glycolipids)
Lipids are heterogenous, amphipathic and thus insoluble
They associate into larger structures and are not usually free in solution (due to the hydrophobic affect)
Due to the potencial to aggregate, lipid storage and transport is a challenge
Lipids classification:
Structure:
-fatty acids (FAs: aliphatic carboxylic acids)
-triacylglycerols (TAGs: 3 FAs esterilidad to glycerol)
-phospholipids (PLs: phosphorus head group
-isoprenoid/steroids (cholesterol)
-glycolipids (glycosphingolipds)
Functions:
-cellular structures (membrane bilayers, vesicles)
-energy storage (fat=triacylglycerols)
-bioactivity (messengers,vitamins, hormones)
Apply the rules of fatty acid nomenclature (both conventional and omega systems) to the identification of FA structures
Omega nomenclature: count the carbons starting from the tail to the first double bond.
Ex: 18:3(n-3)
Delta nomenclature: count the carbons starting from the carbonyl group: list positions of the double bonds (assume cis unless otherwise specified)
Ex:18:3(9,12,15)
Describe fatty acids
They are amphipathic: hydrophilic carboxyl group and hydrophobic hydrocarbon tail of variable leangth
Fas may be saturated (no double bonds), mono- or poly-unsaturated
Most natural unsaturated FAs have unconjugated cis double bonds (¨trans¨ fats mainly derived artificially)
In humans, most FAs are found esterified (CE) to cholesterol or to glycerol (TAGs or PLs) , or are bound to albumin in the blood
Arachidonic acid is the precursor of eicosanoids: bioactive FAs including prostaglandins and thromoboxanes and leukotrienes
Describe the fluid mosaic model of membrane bilayer structure and structural featured of fatty acids and phospholipids that influence membrane properties (fluidity)
The lipid bilayer consists mainly of lipids (PLs, cholesterol) and proteins and is fluid in 2D.
Rotation and lateral diffusion os allowed, but ¨flip-flop¨is rare
Lipid composition is different in the inner vs. outer membrane leaflets.
Double bonds influence the fluidity of lipids (at body temperature)
Membrane fluidity increase with degree of FA chain un saturation, and decreases with FA chain length
Cholesterol also influences membrane fluidity by ¨smoothing¨the transition between solid and liquid phospholipid phases
Explain triacylglycerols
TAGs consist of 3 FAs esterified to glycerol: they are found circulating lipoproteins or in insoluble cytosolic lipids droplets.
In adipose tissue, stored TAG in droplets can be hydrolysis to reales FFA and glycerol for delivery to the liver and other tissues.
TAGs are the major energy reserve in the body
Explain glycerophospholipids
Most phospholipids are esters of 3-glycerophosphate, two FA and a polar head group. They are a major component of cellular membranes and vesicles.
Headgroups vary by charge, cellular location, and effects on membrane curvatures and protein function.
Ex: phosphatidylcholine is the most abundant
Pls are also precursors of lipid second messengers: position specific cleavage of PIP2 by phospholipases generated bioactive molecules such as diacylglycerol and inositol-1,4,5-P3
Exaplain sphingomyelin and glycosphingolipids
Sphingomyelin and glycosphingolipids (cerebroisides, gangliosides) contain a sphingosine backbone; they have signaling or recognition roles and are abundant in the brain
Genetic disorders of glycosphingolipid degradation
Glycosphingolipids are synthesized and degraded in strictly ordered pathways: genetic defects in lysosomal GSL degration causes severe neurodegenerative diseases.
What is cholesterol and why is it important in the body?
Cholesterol is important for maintaining lipid bilayer fluidity.
It’s made from isoprene
Cholesterol is highly insoluble and must be transported in lipoproteins, imbalances in which cause atherosclerosis and vascular diseases.
The liver coordinates intercellular transport and regulation of cholesterol; in humans, cholesterol is excreted, not degraded
How do lipoproteins allow for triacylglycerol and colesterol transport?
TAGs and cholesterol are packaged as lipoproteins when in circulation to allow for transport.
TAG in lipoproteins are used as a fuel source or stored in adipose tissue.
Cholesterol derivatives
Cholesterol is a precursor of bile acids, steroid hormones and vitamin D
Isoprenoids include dolichol and ubiquinone
