Fatty Acid Synthesis and Transport
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Questions and Answers

What is the effect of n-6 PUFA on cholesterol levels?

  • Have no effect on cholesterol levels
  • Lower cholesterol levels (correct)
  • Increase TAG levels
  • Increase cholesterol levels

    • What is associated with an increased risk of CHD?

  • Low levels of TAG
  • High levels of HDL cholesterol
  • High levels of Lipoprotein (a) in plasma (correct)
  • Low levels of LDL cholesterol

    • What is the main component of foam cells?

  • Phospholipids
  • Cholesterol (correct)
  • Proteins
  • Triglycerides

    • What is the effect of oestrogen on Lipoprotein (a) levels?

    <p>Decrease Lipoprotein (a) levels</p> Signup and view all the answers

    What is the role of scavenger receptors in foam cells?

    <p>They take up modified LDL, leading to cholesterol accumulation</p> Signup and view all the answers

    What is the initial stage of atherosclerosis?

    <p>Fatty streak formation</p> Signup and view all the answers

    What is the primary form of lipid storage in the body?

    <p>Triacylglycerol (TAG)</p> Signup and view all the answers

    What is the rate-limiting step in fatty acid synthesis?

    <p>Acetyl CoA to malonyl CoA</p> Signup and view all the answers

    What is the primary source of energy for fatty acid synthesis?

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

    What is the role of insulin in fatty acid synthesis?

    <p>Stimulates acetyl CoA carboxylase</p> Signup and view all the answers

    What is the effect of malonyl CoA on fatty acid oxidation?

    <p>Inhibits fatty acid oxidation</p> Signup and view all the answers

    What is the role of citrate in fatty acid synthesis?

    <p>Is a precursor to malonyl CoA</p> Signup and view all the answers

    What is the primary site of fatty acid synthesis?

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

    What is the role of oxaloacetate in fatty acid synthesis?

    <p>Is a precursor to citrate</p> Signup and view all the answers

    What is the primary function of Fatty acid synthetase in fatty acid synthesis?

    <p>To catalyze the synthesis of fatty acids from acetyl CoA and malonyl CoA</p> Signup and view all the answers

    Which of the following lipoproteins is responsible for carrying dietary triglycerides from the intestine to the liver?

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

    What is the primary role of apoproteins in lipoprotein metabolism?

    <p>To recognize and bind to specific receptors on cell surfaces</p> Signup and view all the answers

    What is the rate-limiting step in cholesterol synthesis?

    <p>The conversion of HMG-CoA to mevalonate</p> Signup and view all the answers

    What is the consequence of a deficiency in LDL receptors?

    <p>Very high blood cholesterol levels and premature death from atherosclerosis</p> Signup and view all the answers

    Which of the following is an example of a genetic hyperlipoproteinaemia?

    <p>Familial hypercholesterolaemia</p> Signup and view all the answers

    What is the primary function of lipoprotein lipase?

    <p>To hydrolyze triglycerides into fatty acids and glycerol</p> Signup and view all the answers

    What is the primary mechanism by which statins inhibit cholesterol synthesis?

    <p>By inhibiting the activity of HMG-CoA reductase</p> Signup and view all the answers

    Study Notes

    Lipid Synthesis and Transport

    • Energy from excess food is stored as glycogen (carbohydrate) and triacylglycerol (TAG) in the liver and adipose tissue, respectively.
    • Insulin stimulates fatty acid synthesis from acetyl CoA in the fed state.
    • The first step in fatty acid synthesis is the conversion of acetyl CoA to malonyl CoA, catalyzed by acetyl CoA carboxylase, which is the rate-limiting step and inhibited by carnitine transferase.

    Fatty Acid Synthesis

    • Fatty acid synthesis requires NADPH, which is provided by the hexose monophosphate shunt.
    • Fatty acid synthetase is the enzyme responsible for fatty acid synthesis.

    TAG Synthesis

    • TAG is synthesized from glycerol phosphate and three fatty acids in the liver cell.
    • Apoproteins are involved in the synthesis of TAG.

    Lipoprotein Structure

    • Lipoproteins have an inner core containing triglycerides and cholesterol esters, surrounded by a single layer of phospholipids, cholesterol, and apoproteins.
    • Lipoproteins are necessary for lipid transport in the blood, as lipids are insoluble in water.

    Classes of Lipoproteins

    • Chylomicrons: largest and lowest density lipoproteins, carrying mainly dietary TAG.
    • VLDL (Very Low Density Lipoprotein): carries mainly endogenous TAG.
    • LDL (Low Density Lipoprotein): carries mainly cholesterol to the tissues.
    • HDL (High Density Lipoprotein): carries mainly cholesterol from the tissues to the liver.

    Cholesterol Synthesis

    • Cholesterol synthesis is controlled by its own synthesis and the number of LDL receptors on the cell surface.
    • The rate-limiting step in cholesterol synthesis is the conversion of HMG-CoA to mevalonate, which is inhibited by statins.

    LDL Receptors

    • LDL receptors are important for removing LDL from the circulation through receptor-mediated endocytosis.
    • Deficiency of LDL receptors leads to familial hypercholesterolaemia and very high blood cholesterol levels.

    Hyperlipidaemias

    • Hypercholesterolaemia: high levels of cholesterol in the blood.
    • Hypertriglyceridaemia: high levels of triglycerides in the blood.
    • Genetic disposition and environmental factors (diet, lifestyle) can contribute to hyperlipidaemias.

    Examples of Genetic Hyperlipoproteinaemias

    • Defective LDL receptor: high LDL in blood.
    • Lipoprotein lipase deficiency: high chylomicrons and VLDL.
    • Deficiency of C-II: high chylomicrons and VLDL.
    • Deficiency of apoproteins involved in remnant uptake: high chylomicron and VLDL remnant.

    Risk Factors for Secondary Hyperlipoproteinaemias

    • Obesity.
    • Diabetes mellitus type 2.
    • Dietary cholesterol and fatty acid (SFA vs PUFA).
    • Alcoholism.

    Lipoprotein (a)

    • Lp(a) is associated with increased risk of CHD.
    • Lp(a) is a lipoprotein containing LDL and apoprotein a.

    Atherosclerosis

    • Atherosclerosis is a complex process involving inflammation and proliferation of smooth muscle in the artery wall.
    • Plaque formation is the result of foam cell accumulation, which is rich in cholesterol.

    Modified LDL

    • Modified (oxidised) LDL is not recognised by the normal receptor but is taken up by scavenger receptors in foam cells, leading to accumulation of cholesterol.

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    Description

    Learn about the process of fatty acid synthesis, its regulation, and transport in the body. Understand the role of insulin, acetyl CoA, and malonyl CoA in this process.

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