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Lipids. “Fat, what good is it?”. Lipids. Biomolecules soluble in organic solvents Roles Nutritional Structural regulatory. Types of Lipids. Glycerol-based Sphingolipids Steroids Eicosanoids/leukotrienes. Storage Lipids. Fatty acids Saturated and Unsaturated

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Lipids

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Lipids

“Fat, what good is it?”


Lipids

  • Biomolecules soluble in organic solvents

  • Roles

    • Nutritional

    • Structural

    • regulatory


Types of Lipids

  • Glycerol-based

  • Sphingolipids

  • Steroids

  • Eicosanoids/leukotrienes


Storage Lipids

  • Fatty acids

    • Saturated and Unsaturated

      • Relationship to melting point

  • Triacylglycerides

    • Glycerol + 3 fatty acids

  • Waxes


Glycerol based fats

  • Glycerol on the left

  • Esterifies to 3 fatty acids


Triacylglyerides

  • Glycerol in blue

  • Fatty acids in red

  • Condensation produces 3 water molecules

  • Very nonpolar…excludes water


Lipids in Membranes:

  • Phospholipids

  • Cholesterol

  • Glycolipds: Sugar group attached

  • Proteins: either integral or peripheral

  • Sphingolipids


Phosphoacylglycerols

  • Glycerol esterified to 2 fatty acids.

  • Third position is phosphate

  • Other end of phosphate can combine with other molecules to form various derivatives

  • amphipathic


Phosphoacylglycerols


Derivatives of Phosphoacylglycerols (PAG)


Phosphatidyl choline with fatty acids as oleate and palmitate


Sphingolipids

  • Sphingosine instead of glycerol

  • Derivatized at ester C1

  • Fatty acids added at amine

  • Different types are found in plasma membrane and myelin sheaths

  • Gangliosides

    • cell to cell interactions

    • antigenic


Sphingosine


Sphingolipids


Sphingophospholipid with choline and the fatty acid as linolenic


Cholesterol


Role of Cholesterol

  • Keeps the lipids in membrane from aggregrating: Keeps the membrane intact as a bilayer

  • Precursor to Bile Acids

    • Act as detergentsto dissolve dietary fats

    • Fats can be broken better by enzymes

  • Precursor to steroid hormones that regulate gene expression

  • Precursor to Vitamin D


Good vs. Bad Cholesterol

  • Related to lipoproteins (protein + lipid complexes)

  • Dietary excess fat is packaged into VLDL

  • Fat cells (adipose cells) take these up convert to fatty acids

  • Some VLDL is converted to LDL

  • LDL is very rich in Cholesterol


LDL

  • Too much LDL can circulate in the blood

  • Build up in arteries; lead to heart attack


HDL

  • Another lipoprotein that converts cholesterol into a lipoprotein that returns to the liver ; Removes cholesterol out of the bloodstream;

  • believed to prevent heart attacks


Ratio of LDL to HDL

  • LDL cholesterol of less than 100 mg/dL is the optimal level. Less than 130 mg/dL is near optimal for most people.

  • A high LDL level (more than 160 mg/dL or 130 mg/dL or above if you have two or more risk factors for cardiovascular disease) reflects an increased risk of heart disease

  • Low HDL cholesterol levels [less than 40 mg/dL] is thought to increase the risk for heart disease.


Steroid hormones


Eicosanoids

  • Prostaglandins: different types

    • Some stimulate contraction of smooth muscle during menstruation and labor

    • Others produce fever and inflammation and pain

  • Thromboxanes: act in the formation of blood clot

  • Leukotrienes: induces contraction of the muscle lining the lungs

    • overproduction leads to asthma


Eicosanoids/Leukotrienes


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