Lipids
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Questions and Answers

What are important short chain fatty acids

Acetic acids C2 and butyric acid C4

What are important long chain fatty acids?

Palmitic acid C16 and stearic acid C18

What is the biomedical importance of saturated fatty acids?

It leads to higher cholesterol and higher atherosclerosis so higher incidence of coronary heart disease

Which type of unsaturated fatty acids is liquid at room temperature?

<p>Cis type</p> Signup and view all the answers

What’s the difference between saturated fatty acids and unsaturated fatty acids?

<p>Saturated: No double bond. Unsaturated: Double bonds</p> Signup and view all the answers

What type of fatty acids only contains one double bond?

<p>Monoenoic</p> Signup and view all the answers

what are important monoenoic fatty acids?

<p>Palmitoleic acid ( 16:1) and Oleic (18:1)</p> Signup and view all the answers

what is the importance of monoenoic fatty acids?

<p>Lower plasma cholesterol —&gt; lower atherosclerosis and coronary heart disease</p> Signup and view all the answers

What are important w6 PUFA’s?

<p>Linoleic acid (18:2) ( is the parent FA) and Arachidonic acid (20:4)</p> Signup and view all the answers

What are important w3 PUFAs?

<p>Linolenic acid (18:3) (parent FA)</p> Signup and view all the answers

What is he importance of PUFAs?

<p>Lower plasma cholestorol —&gt; lower atherosclerosis and CHD (w3 and w6) but w3 has more importance since it lowers BP, Plasma TAG and tendency of thrombosis</p> Signup and view all the answers

What are essential FA?

<p>a-Linolenic and Linoleic</p> Signup and view all the answers

What are the 2 types of Eicosanoids?

<p>Cyclic: Prostaglandin PG, Prostacyclin PGI, Thromboxanes TX Non-cyclic: Leukotriens LT, Lipoxis LX</p> Signup and view all the answers

Which enzyme is needed to form Thromboxane TXA2 from Prostaglandin?

<p>Thromboxane synthase</p> Signup and view all the answers

Which enzyme is needed to form Prostaglandin from Arachidonic acid?

<p>Prostaglandin H synthase</p> Signup and view all the answers

Which enzyme is needed to form Leukotrienes from Arachidonic acid?

<p>Lipoxygenase</p> Signup and view all the answers

What are the main functions of PGE2?

<ul> <li>Vasodilatation - Smooth muscle relaxation - Mediator of inflammatory reactions</li> </ul> Signup and view all the answers

What are the main functions of TXA2?

<ul> <li>Vasoconstriction - higher platelet aggregation</li> </ul> Signup and view all the answers

What are the main functions of PGI2?

<ul> <li>Vasodilatation - Inhibits platelet aggregation</li> </ul> Signup and view all the answers

What are the main functions of Leukotrienes?

<ul> <li>stimulate inflammatory reactions - components of slow reacting substance of anaphylaxis (SRS-A)</li> </ul> Signup and view all the answers

What are the main functions of Lipoxins?

<ul> <li>Anti-inflammatory - decrease immune response</li> </ul> Signup and view all the answers

What are the actions of SAIDs?

<p>Inhibit phospholipase activity (decrease availability of arachidonic acid)</p> Signup and view all the answers

What are the actions of NSAIDs?

<p>Inhibit prostaglandin production by inhibiting cyclooxygenase</p> Signup and view all the answers

What is the definition of simple lipids?

<p>Esters of FA with alcohol</p> Signup and view all the answers

What is the definition of simple lipids?

<p>Esters of FA with alcohol</p> Signup and view all the answers

What are the types of simple lipids?

<p>Neutral fat (TAG) and Waxes</p> Signup and view all the answers

What are the compounds of natural fats/ TAG?

<p>Esters of 3 FA and the alcohol is Glycerol</p> Signup and view all the answers

What are the compounds of natural fats/ TAG?

<p>Esters of 3 FA and the alcohol is Glycerol</p> Signup and view all the answers

What are the compounds of waxes?

<p>1 FA and long chain alcohols</p> Signup and view all the answers

What are the most important waxes?

<p>Cholestorol esters, Vitamin A esters (Retinol), Vitamin D esters (Calciferol)</p> Signup and view all the answers

What’s the definition of Compound lipids?

<p>Simple lipid conjugated with another group</p> Signup and view all the answers

What are the classifications of compound lipids?

<p>Phospholipid: contains phosphate and Glycolipid: contains carbohydrate</p> Signup and view all the answers

What are phospholipids classified into?

<p>Glycerophospholipids and Sphingomyelin</p> Signup and view all the answers

What are Glycerophospholipids?

<p>Phospholipids containing glycerol and alcohol</p> Signup and view all the answers

What is the compound of phosphatidic acid?

<p>SFA at position 1 and USFA at position 2</p> Signup and view all the answers

What is the compound of Lecithin?

<p>Phosphatidic acid + choline</p> Signup and view all the answers

What is the compound of Cephalin?

<p>Phosphatidic acid + Ethanolamine</p> Signup and view all the answers

What is the compound of Phosphatidyl serine?

<p>Phosphatidic acid + serine</p> Signup and view all the answers

What is the compound of Phosphatidyl Inositol aka Lipositol?

<p>Phosphatidic acid + Inositol</p> Signup and view all the answers

What is the compound of Plasmalogens?

<p>Resembles lecithin and cephalin but fatty alcohol at position 1 instead of FA</p> Signup and view all the answers

What is the compound of Cardiolipins?

<p>2 Phosphatidic acid connected by 1 Glycerol (4 FA + 3 Glycerol + 2 Phosphate)</p> Signup and view all the answers

What is the compound of Phosphatidyl glycerol?

<p>Phosphatidic acid + Glycerol</p> Signup and view all the answers

What are Phospholipases and what do they do?

<p>Hydrolyze Phospholipids at 4 positions (only 3 in human): Phospholipase A1/A2/C/D</p> Signup and view all the answers

Why does snake venom cause death?

<p>Contains Lecithinase (Phospholipase A2) that converts Phospholipids in CM of RBCs to Lysophospholipids, causing Hemolysis</p> Signup and view all the answers

What is the compound Sphingomyelin?

<p>Ceramide + Phosphate + Choline</p> Signup and view all the answers

What are the common functions of phospholipids? (Select all that apply)

<p>Form micelles in water</p> Signup and view all the answers

What does lecithin provide for the synthesis of acetylcholine?

<p>Choline</p> Signup and view all the answers

Lecithin deficiency can lead to Respiratory Distress Syndrome (RDS).

<p>True</p> Signup and view all the answers

What are the components of glycolipids?

<p>Ceramide (sphingosine + fatty acid) + carbohydrate</p> Signup and view all the answers

Where is cerebroside primarily found in the body?

<p>Brain tissue</p> Signup and view all the answers

Cholesterol can be derived from both ______ and ______ sources.

<p>exogenous, endogenous</p> Signup and view all the answers

What is the primary function of cholesterol within cell membranes?

<p>It moderates membrane fluidity.</p> Signup and view all the answers

What are steroids divided into? (Select all that apply)

<p>Sterols</p> Signup and view all the answers

What is a key role of lecithin in the human body?

<p>Provides choline for synthesis of acetylcholine</p> Signup and view all the answers

Which of the following statements regarding phospholipid bilayer fluidity is true?

<p>Unsaturated fatty acids help maintain membrane fluidity</p> Signup and view all the answers

What does a Lecithin/Sphingomyelin ratio above 2 indicate?

<p>Fetal lung maturity</p> Signup and view all the answers

What types of glycolipids are known to exist?

<p>Cerebrosides, sulfolipids, gangliosides</p> Signup and view all the answers

What is a major source of endogenous cholesterol?

<p>Liver and red blood cells</p> Signup and view all the answers

What is an important function of cardiolipins?

<p>Facilitating mitochondrial energy metabolism</p> Signup and view all the answers

What are the two primary types of derived lipids?

<p>Fatty acids and steroids</p> Signup and view all the answers

What are sulfolipids primarily found in?

<p>Liver, muscles, and testicles</p> Signup and view all the answers

Study Notes

Phospholipid Compounds

  • Phosphatidic Acid: Consists of a glycerol backbone, two fatty acid chains (SFA at position 1 and USFA at position 2), and a phosphate group.
  • Lecithin: Composed of phosphatidic acid linked to choline.
  • Cephalin: Formed by connecting phosphatidic acid to ethanolamine.
  • Phosphatidyl Serine: Contains phosphatidic acid bound to serine.
  • Phosphatidyl Inositol (Lipositol): Consists of phosphatidic acid attached to inositol.
  • Plasmalogens: Similar structure to lecithin and cephalin but have a fatty alcohol at position 1 instead of a fatty acid.
  • Cardiolipins: Two phosphatidic acid molecules linked by one glycerol molecule, resulting in four fatty acid chains, three glycerol molecules, and two phosphate groups.
  • Phosphatidyl Glycerol: Composed of phosphatidic acid linked to glycerol.

Phospholipases and their Actions

  • Phospholipases: Enzymes that hydrolyze phospholipids at specific positions on their structure.
  • Human Phospholipases: Primarily operate at three positions: Phospholipase A1, A2, and C.

Snake Venom and Hemolysis

  • Snake Venom: Contains lecithinase (phospholipase A2), an enzyme that converts phospholipids in the cell membrane (CM) of red blood cells (RBCs) into lysophospholipids.
  • Lysophospholipids: Disrupt the structure of the RBC membrane, leading to hemolysis (rupture of red blood cells).

Sphingomyelin

  • Sphingomyelin: A phospholipid composed of ceramide linked to phosphate and choline.

Phospholipids

  • Amphipathic molecules with both polar and nonpolar groups, forming micelles in water
  • Essential for cell membrane fluidity, forming the phospholipid bilayer
  • Unsaturated fatty acids (USFA) with double bonds create kinks, preventing close packing and increasing membrane fluidity
  • Saturated fatty acids (SFA) pack tightly, resulting in lower membrane fluidity
  • Involved in emulsification of fats, breaking large fat globules into smaller droplets for easier digestion
  • Hydrotropic substances prevent cholesterol precipitation
  • Arachidonic acid is a precursor for eicosanoid synthesis

Specific Phospholipid Functions

  • Lecithin provides choline for the synthesis of acetylcholine, a neurotransmitter
  • Lecithin acts as a lung surfactant, reducing surface tension between air and the alveolar membrane
  • Plasmalogens, found in cell membranes, are associated with Alzheimer's disease when their levels are reduced
  • Phosphatidyl glycerol is crucial in the synthesis of cardiolipin
  • Phosphatidyl inositol acts as a second messenger in hormone signaling (signal transduction)
  • Involved in blood clotting: Platelet Activating Factor (PAF) is a choline plasmalogen, while cephalin promotes thrombin formation
  • Cardiolipin plays a role in mitochondrial energy metabolism

Lecithin and Lung Surfactant

  • Lecithin reduces surface tension in the alveoli, preventing collapse
  • Deficiency of Lecithin causes Respiratory Distress Syndrome (RDS) in newborns
  • The Lecithin/Sphingomyelin (L/S) ratio indicates fetal lung maturity
  • The L/S ratio stays relatively equal until 32-33 weeks of gestation
  • After 32-33 weeks, Lecithin levels increase, leading to an L/S ratio greater than 2, indicating fetal lung maturity
  • An L/S ratio below 1.5 suggests an increased risk of RDS

Glycolipids

  • Composed of ceramide (sphingosine + fatty acid) and a carbohydrate
  • Classified into:
    • Cerebrosides: ceramide + glucose or galactose
    • Sulfolipids (sulfatides): ceramide + galactose-3-sulfate
    • Gangliosides: ceramide + complex carbohydrate radicals

Distribution of Glycolipids

  • Cerebrosides are primarily found in brain tissue
  • Sulfolipids are present in the liver, muscles, and testes

Derived Lipids

  • Result from the hydrolysis of simple or compound lipids
  • Examples include fatty acids, alcohols, steroids, carotenoids, and fat-soluble vitamins

Steroids

  • Divided into sterols, bile acids, and steroid hormones

Zoosterols

  • Found in animals and humans as cholesterol

Cholesterol Sources and Distribution

  • Exogenous sources: brain, egg yolk, liver, and meat
  • Endogenous sources: red blood cells and all other cells can synthesize cholesterol
  • Distributed throughout all tissues, but primarily in nervous tissue, liver, adrenal glands, and gonads
  • Plasma cholesterol is synthesized primarily in the liver, with a normal range of 120-200 mg/dL (30% cholesterol, 70% cholesterol ester)

Cholesterol Importance

  • Forms bile acids/salts in the liver for fat digestion
  • Precursor to steroid hormones
  • Involved in Vitamin D3 (cholecalciferol) synthesis
  • Regulates membrane fluidity by preventing excessive movement of fatty acid tails at high temperatures and preventing close packing of phospholipids at low temperatures

Phospholipid Functions

  • Amphipathic molecules containing both polar and nonpolar groups.
  • Form micelles in water
  • Contribute to cell membrane fluidity by forming phospholipid bilayers.
  • Unsaturated fatty acids (USFA) with double bonds create kinks, increasing membrane fluidity.
  • Saturated fatty acids (SFA) interact strongly, leading to lower membrane fluidity.
  • Emulsify fat, breaking down large fat globules into smaller droplets for easier digestion.
  • Play a role in plasma protein formation.
  • Act as hydrotropic substances preventing cholesterol precipitation.
  • Arachidonic acid is a precursor for the synthesis of eicosanoids.

Specific Phospholipid Functions

  • Lecithin provides choline for the synthesis of acetylcholine, a neurotransmitter.
  • Lecithin acts as a lung surfactant.
  • Plasmalogens are present in cell membranes and reduced levels are associated with Alzheimer's disease.
  • Phosphatidyl glycerol is crucial for the synthesis of cardiolipin.
  • Phosphatidyl inositol acts as a second messenger for hormones, involved in signal transduction.
  • Involved in blood clotting:
    • Platelet Activating Factor is a choline plasmalogen.
    • Cephalin promotes thrombin formation.
  • Cardiolipins are involved in mitochondrial energy metabolism.

Lecithin as a Lung Surfactant

  • Reduces surface tension between air and the alveolar membrane.
  • Deficiency of Lecithin leads to Respiratory Distress Syndrome (RDS).
  • Lecithin/Sphingomyelin (L/S) ratio indicates fetal lung maturity.
  • L/S ratio remains equal until 32-33 weeks of gestation.
  • Lecithin levels increase after 32-33 weeks.
  • L/S ratio above 2 signifies fetal lung maturity.
  • L/S ratio below 1.5 indicates RDS.

Glycolipids

  • Composed of ceramide (sphingosine + fatty acid) + carbohydrate.

Types of Glycolipids

  • Cerebrosides (ceramide + glucose/galactose): found in brain tissue.
    • Glucocerebroside and galactocerebroside.
  • Sulfolipids (sulfatide) (ceramide + galactose 3 sulfate): found in liver, muscles, and testicles.
  • Ganglioside (ceramide + complex carbohydrate radicals).

Derived Lipids

  • Products of hydrolysis of simple or compound lipids.
  • Examples include fatty acids, alcohols, steroids, carotenoids, and fat-soluble vitamins.

Steroids

  • Divided into sterols, bile acids, and steroid hormones.

Zoosterols

  • Found in animals and humans as cholesterol.

Cholesterol Sources

  • Exogenous: brain, egg yolk, liver, meat.
  • Endogenous: red blood cells and every cell can synthesize cholesterol.

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