Integration of Metabolism Lecture 10
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Questions and Answers

What happens to the constituent parts of carbohydrates, fats, and proteins after digestion?

  • They are stored in the muscles
  • They are excreted from the body
  • They are destroyed by the liver
  • They are transported across the intestinal wall and enter the bloodstream or lymphatic system (correct)

    • What is the primary reason why our body needs to store energy?

  • To store excess energy for times of fasting and starvation
  • To facilitate digestion and absorption of nutrients
  • To use immediately after eating
  • To meet the constant demand for energy from organs like the brain (correct)

    • What is the name of the state that occurs after a meal when the body is digesting and absorbing nutrients?

  • Fasting state
  • Absorptive state (correct)
  • Starvation state
  • Fed state

    • During the absorptive state, what happens to anabolism and catabolism?

    <p>Anabolism exceeds catabolism</p> Signup and view all the answers

    Where does the digestion of carbohydrates begin?

    <p>In the mouth</p> Signup and view all the answers

    What would happen if there were no method in place to store excess energy?

    <p>We would need to eat constantly</p> Signup and view all the answers

    Where are the absorbed nutrients transported to from the intestines?

    <p>Liver, adipose tissue, or muscle cells</p> Signup and view all the answers

    What stimulates the release of insulin into the bloodstream?

    <p>The ingestion of food and the rise of glucose concentrations in the bloodstream</p> Signup and view all the answers

    What is glucose immediately converted into once inside the liver, adipose, and muscle cells?

    <p>Glucose-6-phosphate</p> Signup and view all the answers

    What is the purpose of the concentration gradient established by the conversion of glucose into glucose-6-phosphate?

    <p>To allow glucose to continue moving from the blood to the cells</p> Signup and view all the answers

    What is the role of insulin in muscle cells?

    <p>To promote the synthesis of protein</p> Signup and view all the answers

    What happens to the dietary fats and sugars ingested shortly after eating?

    <p>They are processed and used immediately for energy</p> Signup and view all the answers

    What happens when the carbon sources for gluconeogenesis are depleted?

    <p>Proteins from muscles are released and broken down for glucose synthesis</p> Signup and view all the answers

    What is the universal currency of energy in the cell?

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

    What is the purpose of integrating metabolism?

    <p>To ensure a supply of energy for all tissues at all times</p> Signup and view all the answers

    What is the result of a positive caloric balance?

    <p>A significant proportion of food energy intake is stored as either glycogen or fat</p> Signup and view all the answers

    What is the function of NADPH in metabolism?

    <p>Reductive biosynthesis</p> Signup and view all the answers

    What is the common intermediate in the metabolism of macromolecules?

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

    What is the first priority for survival when the body is deprived of nourishment for an extended period of time?

    <p>Provide enough glucose or fuel for the brain</p> Signup and view all the answers

    Which of the following is NOT used as a source for gluconeogenesis during starvation?

    <p>Fatty acids from adipose tissue</p> Signup and view all the answers

    What is the primary source of fuel for the heart and other organs after several days of starvation?

    <p>Ketone bodies</p> Signup and view all the answers

    What process is shut off in cells that can use alternative fuels during starvation?

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

    What is the fate of pyruvate, lactate, and alanine from muscle cells during starvation?

    <p>They are used to synthesize glucose in the liver</p> Signup and view all the answers

    What is the primary role of ketones during starvation?

    <p>To provide energy for the brain and other glucose-dependent organs</p> Signup and view all the answers

    What is the primary fuel source for the heart muscle?

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

    What happens to pyruvate in skeletal muscle cells?

    <p>It is converted to lactate and alanine</p> Signup and view all the answers

    What is the function of hormone-sensitive lipase in adipose tissue?

    <p>To break down triacylglycerol</p> Signup and view all the answers

    What is the brain's primary fuel source under normal conditions?

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

    What is unique about heart muscle metabolism compared to skeletal muscle?

    <p>It can only function under aerobic conditions</p> Signup and view all the answers

    What is the brain's adaptation during fasting conditions?

    <p>It adapts to use ketone bodies as fuel</p> Signup and view all the answers

    Study Notes

    Absorptive State

    • The absorptive state occurs after a meal when the body is digesting food and absorbing nutrients.
    • During this state, anabolism exceeds catabolism, and the body stores energy for later demands.
    • The digestion of carbohydrates begins in the mouth, while the digestion of proteins and fats begins in the stomach and small intestine.

    Insulin and Glucose Absorption

    • Insulin is released by pancreatic beta cells in response to increased glucose concentrations in the bloodstream.
    • Insulin initiates the absorption of blood glucose by liver hepatocytes, adipose, and muscle cells.
    • Glucose is converted into glucose-6-phosphate inside these cells, establishing a concentration gradient that allows glucose to continue moving from the blood to the cells.

    Energy Storage and Use

    • If energy is needed shortly after eating, dietary fats and sugars are processed and used immediately for energy.
    • This prevents the continued breakdown of proteins that serve as carbon sources for gluconeogenesis.
    • Once these stores are fully depleted, proteins from muscles are released and broken down for glucose synthesis.
    • Overall survival is dependent on the amount of fat and protein stored in the body.

    Integration of Metabolism

    • The integration of metabolism refers to the co-ordination of the three metabolites (carbohydrates, lipids, and proteins).
    • Its significance lies in ensuring a supply of suitable energy for all tissues at all times.
    • ATP is the universal currency of energy, generated by the oxidation of glucose, fatty acids, and amino acids.

    Starvation

    • When the body is deprived of nourishment for an extended period, it goes into “survival mode.”
    • The first priority is to provide enough glucose or fuel for the brain.
    • The second priority is the conservation of amino acids for proteins.
    • The body uses ketones to satisfy the energy needs of the brain and other glucose-dependent organs.

    Tissue-Specific Metabolism

    • Adipose tissue stores triacylglycerol, which is continuously synthesized and broken down, controlled by hormonal sensitive lipase.
    • Glucose is needed to synthesize triacylglycerol, and glucose levels determine if fatty acids are released into the blood.
    • Heart muscle metabolism is different from skeletal muscle in three ways: it can only function under aerobic conditions, it cannot store glycogen, and fatty acids are the preferred fuel.
    • Brain metabolism is characterized by a very high respiratory rate, and it normally uses glucose as its sole preferred fuel.

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    Description

    Learn about the integrated metabolism of carbohydrates, proteins, and fats, and how the body meets its constant demand for energy through storage and processing of food.

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