Overview of Lipid Biochemistry Flashcards Preview

DEMS: Unit II > Overview of Lipid Biochemistry > Flashcards

Flashcards in Overview of Lipid Biochemistry Deck (29)
Loading flashcards...




Characteristics of cholesterol structure





Characteristics of phospholipid structure

  • hydrophillic head
  • fatty acid chains = hydrophobic



fatty acid


Characteristics of Fatty Acid Structure

  • hydrocarbon chain
  • saturated vs. unsaturated
  • carboxyl group


Chemical properties of lipids

  • less polar than gluocse or amino acids
  • not water soluble


Fatty acids: chemical properties & sources

  • Chem prop
    • Most polar
  • Sources
    • Acetyl CoA → de novo lipogenesis
    • Diet for essential fatty acids
    • Sugars, AA’s, fats


Phospholipids: chemical properties & sources

  • Chem prop
    • 2nd most polar
  • Sources
    • membranes


Cholesterol: chemical properties & sources

  • Chem prop
    • 3rd most polar
  • Sources
    • Diet
    • Synthesized from Acetyl CoA in liver


Cholesterol ester: chemical properties & sources

  • Chem prop
    • not very polar
  • Cholesterol ester = precursor to cholesterol


Triglycerides: chemical properties & sources

  • Chem prop
    • non polar


Fatty acids: General fxns

  • Float in blood during exercise

  • Major component of cell membranes

  • Store calories

  • Precursors for eicosanoids like prostaglandins, leukotrienes, thromboxanes


Phospholipids: General fxns

form membranes


Cholesterol: General fxns

  • Cell membrane component
  • precursor for steroid proteins
  • bile acids


De Novo lipogenesis pathway (general)

  • glucose is present in the liver or adipose tissue in excess (fed state) undergoes glycolysis to pyruvate
  • ==> mitochodria ==>converted to acetyl CoA
  • ==> citrate ==> leaves the mitochondria
  • ==> fatty acid @ cytoplasm.



De Novo Lipogenesis @ liver & adipose tissue

Liver: Acetyl CoA → Citrate → leaves mitochondria → Acetyl CoA → Malonyl CoA → Fatty Acid

Adipose tissue: Fatty acid + glycerol → Tryglyceride.  Or it can be stored as VLDL.


Beta-oxidation pathway

  • body is in negative energy balance such as (short-term fasting or during exercise)
  • fat = important alternative fuel for muscle and liver in an effort to preserve glucose for the brain.
  • oxidation of fat during fasting provides the energy (ATP) which is needed to fuel gluconeogenesis.  
  • Occurs in mitochondria.
  • Triglycerides in adipose tissue → Fatty acids → Acyl carnine → into mitochondria → Acetyl CoA


Ketogenesis pathway general conditions

  • insulin is very low or absent and counter-regulatory hormones quite high
  • occurs during long-term fasting
  • acetyl CoA produced by beta-oxidation in the liver can take an alternate route and become a ketone body


Purpose of ketogenesis pathway

  • Ketones (3-hydroxybutyrate and acetoacetate) serve as an alternative fuel for the brain and other tissues in states of prolonged dietary “glucose insufficiency” (fasting or low carbohydrate diets).
  • body decides that continuing to break down muscle to provide substrate for gluconeogenesis is counter-productive and the brain begins to use an alternate fuel that comes from fat to preserve lean body mass.


Specific conditions ==> ketogenesis pathway

  • starvation, diabetic ketoacidosis and alcoholic ketoacidosis
  • commonalities btwn these conditions:
    • 1. very low insulin levels
    • 2. high counter-regulatory hormones
    • 3. An abundant source of substrate: fatty acids in the case of fasting and diabetic ketoacidosis, and EtOH in the case of alcoholic ketoacidosis
      • Acetyl CoA produced by both fatty acid and alcohol metabolism 


Characteristics of lipoprotein pathways

  • non polar lipids cholesterol, cholesterol esters, triglyceride and phospholipids do not dissolve in water ==>must move through the blood in some other way
  • They move in particles called lipoproteins that contain apo-lipoproteins and lipids in varying amounts.
  • lipoproteins classified based on differences in composition of varying in size and density


Major lipoprotein pathways

  1. Dietary fat pathway / Chylomicron pathway: triglyceride rich (majority) + phospholipid (minority) particles deliver dietary fat to skeletal muscle and adipose tissue.
  2. VLDL pathway: triglyceride derived from the liver is delivered to skeletal muscle and adipose tissue
  3. HDL pathway: largely functions as a reservoir and transport system for a variety of lipids including cholesterol from the periphery to the liver.


Characteristics of cholesterol synthesis

  • Cholesterol = important component of cell membranes & precursor for steroid hormones & bile acids
    • also causes atherosclerosis.
  • Some cholesterol comes from the diet, but it can also be synthesized from acetyl CoA thru the formation of hydroxymethyl glutaryl CoA.
  • Acetyl CoA → leaves mitochondria → HMG CoA (HMG CoA Reductase) → Mevalonate → Cholesterol


Classes of specialized lipids

  • phospholipids 
  • sphingolipids
  • glycosphingolipids
  • arachidonic acid ==> LTs or PGs/thromboxanes


Characteristics of phospholipids

  • Phospholipids that have a glycerol backbone and a PO4 group attached to one of the positions of the glycerol backbone
  • fxns = cell membranes and lipoprotein particles especially and come in several classes depending on the side chains that are attached to the PO4 group.


Characteristics of sphingolipids

  • Sphingolipids are built on a ceramide backbone.
  • The backbone is unique because it is derived in part from an amino acid (serine), thus it contains a nitrogen atom.


Characteristics of glycosphingolipids

  • Glycosphingolipids have a ceramide backbone
  • also have sugar residues attached to the “head group”.


Characteristics of arachidonic acid derivatives

  • Made from arachidonic acid which can form either leukotrienes or prostaglandins/thromboxanes.
  • important regulatory molecules in a number of cell types involved in inflammation.
  • Cyclo-oxygenase 1 and 2 are the critical enzymes in this synthetic pathway.