Post on 10-Jun-2020
transcript
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Ether Glycerophospholipids
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Platelet-activating Factor
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Glycerophospholipids ‐ Plasmalogens
• Found in the cell membrane
• Structure:
Unsaturated fatty alcohol at C1 connected by ether bond
In mammals: at C3; phosphate + ethanolamine or choline
Sphingolipids
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Ceramide: Fatty Acid joined to Sphingosine
HO‐CH‐CH=CH‐(CH2)12CH3O║
CH‐NH‐C‐(CH2)n‐CH3ICH2‐OH
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Sphingomyelin is Phosphocholine Ester of Ceramide
HO‐CH‐CH=CH‐(CH2)12CH3O║
CH‐NH‐C‐(CH2)n‐CH3ICH2‐O ‐CH2‐CH2‐N(CH3)3
+P
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GLYCEROL
FATTY ACID
FATTY ACID
PHOSPHOACYLGLYCEROL
PHOSPHATE
ALCOHOL
Sphingophospholipids
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Sphingophospholipids –Sphingomyelins & Ceramides
• Sphingomyelins: found in large amounts in brain & nerves
• Structure:– Sphingosine as the alcohol– Two nitrogenous bases: sphingosine itself & choline
– One long‐chain fatty acid– Phosphoric acid
• Ceramides: the amino group of sphingosine is attached to a F.A by an amide linkage
– Found in spleen, liver & RBCs
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Glycolipids Lipids that contain carbohydrate residues
Sphingosine as the alcohol
Contains a very long‐chain fatty acid
They are present in cerebral tissue (cerebrosides)
Classification: number & nature of carbohydrate present;
Glycolipids are Formed by Linking one or More Sugars to Ceramide
Ceramide +
‐Glucose or Galactose Cerebroside
‐Sulfated Galactose Sulfatides
‐Oligosaccharide Globoside
‐Oligosaccharide with NANA Gangliosides
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N‐Acetylneuramininc Acid (NANA)
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Steroid Nucleus
SteroidsA group of lipids that have fused‐ring structure of 3 six‐membered rings, and 1 five‐membered ring
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CH3
CH3CH3
CH3
HO
CH3
Steroids: • Cholesterol: The parent compound of all steroids
• Bile Salts ( Bile Acids)
• Steroid Hormones:
• Vitamin D
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Cholesterol
The most important sterol in animal tissues as free alcohol or in an esterified form (with linoleic, oleic, palmitic acids or other F.A)
Steroid hormones, bile salts &vitamin D are derivatives
Tissues contain different amounts of it that serve a structural & metabolic role (adrenal cortex ≈ 10%, whereas, brain is 2%)
Reduces membrane fluidity
Sources:
Can be synthesized in the body from acetyl‐CoA
In the diet (butter, milk, egg yolk, brain, meat & animal fat)
Does not exist in plants o stabilizing extended chains of FA due to hydrophobic interactions
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Bile acids• They are produced from oxidation of cholesterol in the liver
• Produce cholic and chenodeoxycholic acids
• Get conjugated with glycine (mainly) to produce glycocholic,
• Exist as sodium or potassium salts
Bile acids ‐ functions
• Their function is as follows:
1) Emulsification of lipids during digestion
2) Activation of pancreatic lipase
3) Help digestion & absorption of fat‐soluble vitamins
4) Solubilizing cholesterol in bile & prevent gall stone formation
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Pregnane Group (C21)
Estrane Group (C18) Androstane Group (C19)
Classes of steroid hormones
Class Source of the hormone
Progesta-gens
21 corpus luteum
Glucocorticoids,
21 adrenal cortex
Mineralo-corticoids
21 adrenal cortex
Andro-gens
19 testes
Estrogens 18 ovaries