Triacylglycerols and Body Energy Reserve
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Questions and Answers

What percentage of human body weight is constituted by lipids?

  • 25-30%
  • 15-20% (correct)
  • 5-10%
  • 35-40%

    • What is the main reason triacylglycerols are the body's fuel reserve?

  • They are highly concentrated form of energy (correct)
  • They are non-essential for bodily functions
  • They are found in small quantities in the body
  • They are highly polar and hydrophilic in nature

    • How much energy does one gram of triacylglycerol yield?

  • 9 Cal/g (correct)
  • 2 Cal/g
  • 10 Cal/g
  • 4 Cal/g

    • What is the main difference between the storage of triacylglycerols and glycogen?

    <p>Triacylglycerols are stored in anhydrous form, while glycogen is stored with water</p> Signup and view all the answers

    How much of the body's energy needs can fats support during food deprivation?

    <p>For long periods of time</p> Signup and view all the answers

    What is the process called when triacylglycerol is completely degraded to glycerol and free fatty acids?

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

    What percentage of body lipids are triacylglycerols?

    <p>85-90%</p> Signup and view all the answers

    Where does the activation of fatty acids occur during B-oxidation?

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

    What is the fuel reserve of the body stored in?

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

    What percentage of energy obtained from fat comes from the oxidation of fatty acids?

    <p>95%</p> Signup and view all the answers

    What is the precursor for bile acids and steroid hormones?

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

    During starvation, what happens to the triacylglycerol stored in adipose tissue?

    <p>It is hydrolyzed to free fatty acids</p> Signup and view all the answers

    What is the term for the process of lipolysis of TG and reesterification of FFA to TG?

    <p>Triacylglycerol/fatty acid cycle</p> Signup and view all the answers

    What is the result of the oxidation of fatty acids by B-oxidation?

    <p>The sequential removal of a two carbon fragment</p> Signup and view all the answers

    What is the name of the enzyme that removes a fatty acid from triacylglycerol?

    <p>Hormone sensitive triacylglycerol lipase</p> Signup and view all the answers

    What is the purpose of coenzyme A in B-oxidation?

    <p>To form acyl CoA in the mitochondria</p> Signup and view all the answers

    Study Notes

    Lipids and Body Fuel Reserve

    • Lipids make up approximately 15-20% of human body weight.
    • Triacylglycerols (TG) comprise 85-90% of body lipids and are the most abundant lipids.
    • TG is stored in adipose tissue and serves as the body's energy reserve.

    Why Fat is the Fuel Reserve

    • Triacylglycerols are a highly concentrated form of energy, yielding 9 Cal/g.
    • Fatty acids in TG are in the reduced form, which allows for efficient energy storage.
    • Triacylglycerols are non-polar and hydrophobic, allowing them to be stored in an anhydrous form without water.
    • In contrast, glycogen and proteins are polar and require water for storage.

    Triacylglycerols and Energy Storage

    • One gram of fat stored in the body yields nearly six times as much energy as one gram of (hydrated) glycogen.
    • In a healthy 70 kg adult, approximately 10-11 kg of fat is stored, which corresponds to a fuel reserve of 100,000 Cals.

    Other Important Body Lipids

    • Phospholipids, glycolipids, and cholesterol are major components of cell membranes.
    • Cholesterol is a precursor for bile acids and steroid hormones.

    Mobilization of Fat from Adipose Tissue

    • Triacylglycerol lipase removes fatty acids from TG to form diacylglycerol and eventually glycerol and free fatty acids.
    • This process is known as lipolysis.

    Fate of Free Fatty Acids

    • Free fatty acids are transported in the circulation bound to albumin and enter various tissues for energy production.
    • About 95% of the energy obtained from fat comes from the oxidation of fatty acids.

    Triacylglycerol/Fatty Acid Cycle

    • During starvation, TG stored in adipose tissue is hydrolyzed to free fatty acids for oxidation and energy production.
    • About 65% of these FFA are converted to TG and sent back to adipose tissue for deposition.

    Fatty Acid Oxidation

    • Fatty acids are mostly oxidized by B-oxidation, which involves the sequential removal of a two-carbon fragment, acetyl CoA.
    • B-oxidation involves three stages: activation of fatty acids, transport of fatty acids into mitochondria, and oxidation proper in the mitochondrial matrix.

    Coenzyme A and Fatty Acid Oxidation

    • The coenzyme A used for activation is different from the one that finally combines with fatty acid in the mitochondria to form acyl CoA.
    • The cell has two separate pools (cytosolic and mitochondrial) of coenzyme A.

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    Description

    Learn about triacylglycerols, the body's primary energy reserve, and their storage and function in the human body.

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