Q&N

• Why are lipids indispensable for their structure and function?

  Due to their hydrophobic and nonpolar nature.
• What are the most abundant lipids in our body?

  Triacylglycerols, comprising 85-90% of body lipids.
• Why should fat be the fuel reserve of the body?

  Because triacylglycerols are highly concentrated form of energy yield 9 Cal/g and are non-polar and hydrophobic.
• In which form can lipids be transported?


  In the form of lipoprotein.
• What are the types of lipoproteins and their functions?

  1. Chylomicrons:Synthesis in the intestines and Transport exogenous (dietary) triacylglycerol to various tissue.
  2. Very low density lipoproteins (VLDL): produced in the liver n intestines & Transport endogenously synthesized triacylglycerols.
  3. Low density lipoproteins (LDL): Transport cholesterol from liver to body.
  4. High density lipoproteins (HDL):mostly Synthesis in the live Transport cholesterol from body to liver.
• Which enzyme participates in the degradation of TAG in adipose tissue?

  Hormone sensitive triacylglycerol lipase.
• What are the regulatory hormones in hormone sensitive lipase (HSL)?

  Epinephrine, norepinephrine, glucagon, thyroxine, ACTH.
• Where does the metabolism of fatty acids occur?

  In the liver.
• What is the difference between activation and oxidation of fatty acids?

  Activation occurs in the cytosol, while oxidation occurs in mitochondria.
• Define beta oxidation.

  β-Oxidation is the oxidation of fatty acids on the β-carbon atom.
• What is the role of carnitine in fatty acid oxidation?

  Carnitine is transported across the membrane to mitochondria.
• What is the regulatory enzyme of beta oxidation of fatty acids?

  Carnitine acyltransferase I.
• Define ketogenesis.


  Ketogenesis is the synthesis of ketone bodies.
• Where does ketogenesis occur according to the organ and cell?

  In the liver mitochondria.
• What are the general functions of lipids?

  • Excellent energy reserves
  • Structure of cell membranes
  • Essential fatty acids (EFA)
  • Hormone synthesis
• What are the causes of lipid disorder?

  Shortage and overtaking in lipid intake.
• What are the functions of cholesterol?

  Building block for steroid hormones, vitamin D, and bile acids.
• How can we prevent lipid disorder?

  1. Reduce fat intake
  2. Drink at least 8 glasses of water daily
  3. Increase intake of vegetables, fruits, and whole grains
• What is the difference between lipolysis and lipogenesis?

  Lipolysis is the degradation of triacylglycerol, while lipogenesis is the formation of fat.
• What is the function of glycerol?

  Glycerol serves as a backbone for triglycerides.
• What is the advantage of fatty acid production?

  For energy production during long starvation.
• Which organs are not used as energy sources for fatty acids?

  The brain and erythrocytes.
• What is the difference between Acyl transferase 1 and 2?

  Acyl transferase 1 transfers acyl group to carnitine, while transferase 2 converts acyl-carnitine to acyl CoA.
• What is the meaning of ketonuria?

  Ketonuria is the excretion of ketone bodies in urine.
• Which hormones participate in the regulation of ketogenesis?

  Glucagon stimulates ketogenesis, while insulin inhibits it.
• What are the stages of fatty acid synthesis?

  1. Production of acetyl CoA and NADPH
  2. Conversion of acetyl CoA to malonyl CoA
  3. Reactions of fatty acid synthase complex
• Can we get cholesterol from plant products? Why or why not?

  No, because cholesterol is made in the liver and plants do not have a liver.
• Which lipoprotein cannot be separated by electrophoresis?

  Free fatty acid albumin.
• What are the stages of fatty acid oxidation?

  1. Activation of fatty acids in the cytosol
  2. Transport of fatty acids into mitochondria
  3. β-Oxidation proper in the mitochondrial matrix
• Explain fatty acid activation.

  Fatty acids are activated to acyl CoA by thiokinases or acyl CoA synthetases, requiring ATP, coenzyme A, and Mg$^{2+}$.
• How many steps consist of the transport of Acyl CoA into mitochondria?

  In 4 steps.
• How many compounds do ketone bodies consist of?

  3 compounds: acetone, acetoacetate, and β-hydroxybutyrate.
• What are the precursors for ketone bodies?

  Acetyl CoA.
• What are the stages of ketone bodies synthesis?

  1. Two moles of acetyl CoA condense to form acetoacetyl CoA.
  2. Acetoacetyl CoA combines with another acetyl CoA to produce HMG CoA.
  3. HMG CoA lyase cleaves HMG CoA to produce acetoacetate and acetyl CoA.
  4. Acetoacetate can form acetone or be reduced to β-hydroxybutyrate.
• What are the impacts of lifestyles and use of drugs on lipid metabolism?

  They can affect lipid levels and metabolism significantly.
• What are the causes of hypocholesterolemia?

  Hyperthyroidism, pernicious anemia, malabsorption syndrome, hemolytic jaundice.
• Which lipoprotein is responsible for the transport of cholesterol from the body to the liver?

  HDL.
• Define apoproteins.

  Apoproteins are the protein components of lipoproteins.
• What functions do apoproteins perform?

  1. Act as structural components of lipoproteins.
  2. Recognize cell membrane surface receptors.
  3. Activate enzymes involved in lipoprotein metabolism.
• How can our body convert VLDL to LDL?

  VLDL are metabolized to intermediate density lipoprotein, which is further metabolized to LDL.