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Classification of lipids : 

Classification of lipids Simple lipids (non saponifiable) terpenes, steroids, prostaglandins Complex lipids (saponifiable) acylglycerols waxes Fatty acids phospholipids covalently linked sphingolipids different backbones

Waxes : 

Waxes simple esters of fatty acids (usually saturated) with long chain monohydric alcohols Beeswax – also includes some free alcohol and fatty acids Spermaceti – contains cetyl palmitate (from whale oil) –useful for pharmaceuticals (creams/ointments; tableting and granulation) Carnauba wax – from a palm tree from brazil – a hard wax used on cars and boats

Slide 3: 

Bee’s wax Spermaceti source Carnauba wax source

Phospholipids : 

Phospholipids Have hydrophobic and hydrophilic domains. Structural components of membranes Emulsifying agents Suspended in water they spontaneously rearrange into ordered structures Hydrophobic group to center Hydrophilic group to water (basis of membrane structure)

PhospholipidsPhosphoglycerides : 

PhospholipidsPhosphoglycerides When the third OH of glycerol is esterified to a phosphoric acid or a phosphoric acid ester instead of a carboxylic acid, a phosphoacylglycerol results. Phosphatidic acid Phosphatidyl ester

Phosphatidyl esters : 

Phosphatidyl esters ethanolamine (cephalin) choline (lecitin) serine (phosphatidyl-serine) inositol (phosphatidyl-inositol) Common constituent of membrane lipid Involved in cell signalling

Slide 7: 

Phospholipids Amphipatic molecule

Sphingolipids : 

Sphingolipids These lipids are based on sphingosine, are found in plants and animals, and are common in the nervous system.

Sphingolipids : 

Sphingolipids ceramide N-acylsphingosine sphingomyelin A ceramide with phosphocholine or phosphoethanolamine as head group

Sphingoglycolipids : 

Sphingoglycolipids Attachment of carbohydrates to primary -OH of ceramide Cerebrosides: contain a single moiety, principally galactose Sulfatides: sulfuric esters of galactocerebrosides Gangliosides: contain a complex oligosaccharide moiety

Sphingoglycolipids-2 : 

Sphingoglycolipids-2 a cerebroside These compounds are found in the cell membranes of nerve and brain cells.

Clinical significance of sphingolipids : 

Clinical significance of sphingolipids Blood groups determined by various glycolipids on RBCs

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Membranes – An Overview Continuous, unbroken sheets, enclosing compartments Dynamic structures capable of fusing without losing continuity External membrane: plasma membrane: encloses contents of entire cells Internal membranes: nuclear envelope mitochondrial membranes chloroplast membranes lysosomal membrane endoplasmic reticulum

The Cell Membrane : 

The Cell Membrane Maintains cellular stability and integrity Is a protective and selective barrier Controls and directs cellular activity Each type of cell has a unique membrane composition with varying percentages of lipids, proteins, and some carbohydrates. The currently accepted model of the membrane is the fluid mosaic model of a lipid bilayer.

Composition of Some Membranes : 

Composition of Some Membranes

Components of Membranes : 

Components of Membranes

Membrane Structure : 

Membrane Structure Lipid bilayer Hydrophillic heads in contact with aqueous environment Hydrophobic tails reside in interior of bilayer Cholesterol is a structural component Proteins Integral Peripheral Lipid anchored Dynamic structure

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a. lipid bilayer is core of membrane b. lipid molecules are present in a fluid state capable of rotating and moving laterally within membrane. c. proteins occur as “mosaic” of discontinuous particles. d. some proteins penetrate deeply into, and even through, lipid bilayer. e. membranes are dynamic structures in which components are mobile. Fluid mosaic model

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