Basics of Biochemistry: Hormones
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Questions and Answers

What is the primary method by which hormones travel to their target sites?

  • Through the nervous system
  • Through the lymphatic system
  • Via diffusion through tissues
  • Via the bloodstream (correct)

    • What type of hormones utilize the fixed membrane receptor mechanism?

  • Lipid-soluble hormones
  • Steroid hormones
  • Thyroid hormones
  • Water-soluble hormones (correct)

    • What is the primary mode of transportation for hormones to reach their target sites?

  • Bloodstream (correct)
  • Nervous system
  • Digestive tract
  • Lymphatic system

    • Which hormone is primarily responsible for regulating growth and controlling the functioning of endocrine glands?

    <p>Growth hormone</p> Signup and view all the answers

    Which enzyme is activated when a hormone binds to its specific target receptor in the cell membrane during the fixed membrane receptor mechanism?

    <p>Adenyl cyclase</p> Signup and view all the answers

    What characteristic do all peptide hormones share?

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

    What is the primary function of the parathormone secreted by the parathyroid gland?

    <p>Controlling calcium balance</p> Signup and view all the answers

    What characteristic allows lipid hormones to pass through the plasma membrane?

    <p>They are lipid-soluble</p> Signup and view all the answers

    Which hormones are derived from aromatic amino acids?

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

    What acts as the secondary messenger in the fixed membrane receptor mechanism?

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

    Which tissue in the human body is targeted by retinoid hormones for their regulatory functions?

    <p>Cornea and skin</p> Signup and view all the answers

    What are steroid hormones derived from?

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

    What enzyme deactivates cAMP in the fixed membrane receptor mechanism?

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

    Which of the following is an example of a peptide hormone?

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

    Excessive amounts of which vitamin can cause birth defects, urging caution in its use during pregnancy?

    <p>Vitamin A</p> Signup and view all the answers

    Which of these is a feature of peptide hormones?

    <p>They consist of chains of amino acids</p> Signup and view all the answers

    What type of hormone includes compounds derived from fatty acids that compose the plasma membrane?

    <p>Eicosanoid hormones</p> Signup and view all the answers

    What effect does cAMP have within the cell during the fixed membrane receptor mechanism?

    <p>It activates several enzymatic reactions</p> Signup and view all the answers

    What type of hormone is insulin?

    <p>Peptide hormone</p> Signup and view all the answers

    What is the function of calcitriol in calcium homeostasis?

    <p>Activates synthesis of intestinal Ca2+-binding protein</p> Signup and view all the answers

    Which hormone type contains carbohydrate side chains?

    <p>Glyco-protein hormones</p> Signup and view all the answers

    Which of the following hormones is an example of a lipid hormone?

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

    What component is essential for receptor stimulation in a target cell?

    <p>Specific receptors for the hormone</p> Signup and view all the answers

    Which class of hormones can cross the plasma membrane due to their solubility?

    <p>Lipid hormones</p> Signup and view all the answers

    Lipid and phospholipid-derived hormones are produced from which of the following?

    <p>Linoleic acid and arachidonic acid</p> Signup and view all the answers

    Steroid hormones, such as testosterone, are primarily derived from which substance?

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

    Which monoamine hormone is derived from tryptophan and regulates sleep patterns?

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

    How many iodine atoms are incorporated into thyroid hormones?

    <p>Three or four</p> Signup and view all the answers

    Which of the following is an example of an endocrine hormone?

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

    Hormones that diffuse to neighboring target cells are classified as which type?

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

    What allows cells to respond to very low concentrations of hormone?

    <p>High affinity of hormone-receptor interaction</p> Signup and view all the answers

    Which statement about hormone action specificity is correct?

    <p>It results from structural complementarity between the hormone and its receptor</p> Signup and view all the answers

    What type of molecules utilize the mobile receptor mechanism to initiate biochemical changes in the cell?

    <p>Lipid-soluble hormones</p> Signup and view all the answers

    Where do lipid-soluble hormones bind after diffusing through the plasma membrane?

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

    What is the result of the receptor-hormone complex formation inside the cell?

    <p>Triggering gene transcription in the nucleus</p> Signup and view all the answers

    Which process follows the transcription of DNA initiated by the hormone-receptor complex?

    <p>mRNA translation into protein</p> Signup and view all the answers

    What is the final outcome of the mobile receptor mechanism on cell activity?

    <p>Changes due to new protein activity</p> Signup and view all the answers

    Which cellular component is primarily involved in the translation of mRNA into protein during the mobile receptor mechanism?

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

    What activates the enzyme adenyl cyclase in the fixed membrane receptor mechanism?

    <p>The binding of the hormone to the target receptor</p> Signup and view all the answers

    What acts as the secondary messenger in the fixed membrane receptor mechanism?

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

    Where is the receptor located in the mobile receptor mechanism?

    <p>Inside the cytoplasm</p> Signup and view all the answers

    What is the final result of the mobile receptor mechanism?

    <p>Synthesis of new proteins</p> Signup and view all the answers

    Which type of hormones utilize the mobile receptor mechanism?

    <p>Lipid-soluble hormones like estradiol</p> Signup and view all the answers

    What is the role of phosphodiesterase in the fixed membrane receptor mechanism?

    <p>To deactivate cAMP</p> Signup and view all the answers

    Which step involves the conversion of ATP to cAMP in the fixed membrane receptor mechanism?

    <p>The activation of adenylyl cyclase</p> Signup and view all the answers

    In the mobile receptor mechanism, the hormone-receptor complex binds to what in the nucleus?

    <p>Specific DNA sequences</p> Signup and view all the answers

    Study Notes

    Chemistry of Hormones

    • Hormones are chemical messengers released by cells or glands that affect cells in other parts of the body.
    • Hormones are released into the bloodstream and travel to target sites.
    • The target cell has specific receptors for a given hormone, which triggers a change in cell activity.
    • Receptor stimulation may send feedback to the original hormone-producing cell.

    Types of Hormones

    • There are three classes of hormones: peptide hormones, lipid hormones, and monoamine hormones.

    Peptide Hormones

    • Consist of short or long chains of amino acids.
    • Examples include vasopressin, insulin, and follicle-stimulating hormone.
    • Are water-soluble and cannot pass through the plasma membrane alone.

    Lipid Hormones

    • Include steroid and eicosanoid hormones.
    • Are lipid-soluble and can pass through the plasma membrane.
    • Steroid hormones are derived from cholesterol and eicosanoid hormones from fatty acids.

    Monoamines

    • Are derived from aromatic amino acids like phenylalanine, tyrosine, and tryptophan.

    Mechanism of Hormone Action

    • The mechanism of hormone action is grouped into two classes:
      • Fixed membrane receptor mechanism
      • Mobile receptor mechanism

    Fixed Membrane Receptor Mechanism

    • Shown by water-soluble hormones that are amines or proteins in composition (e.g., growth hormone, oxytocin, ADH).
    • Hormones cannot pass through the lipid membrane.
    • Hormones bind to target receptors on the cell membrane, activating adenyl cyclase.
    • cAMP acts as a secondary messenger, diffusing through the cell membrane and activating enzymatic reactions.
    • cAMP is deactivated by phosphodiesterase.

    Mobile Receptor Mechanism

    • Shown by lipid-soluble hormones that are steroids or thyroid hormones (e.g., testosterone, estradiol, aldosterone).
    • Hormones can easily pass through the lipid membrane.
    • Hormones bind to receptors present inside the cytoplasm.
    • The hormone-receptor complex enters the nucleus and binds to specific DNA sequences, leading to gene activation and protein synthesis.
    • Newly synthesized proteins change cell activity.

    Classification of Hormones

    • Endocrine hormones are released into the blood and carried to target cells throughout the body (e.g., insulin and glucagon).
    • Paracrine hormones are released into the extracellular space and diffuse to neighboring target cells (e.g., eicosanoid hormones).
    • Autocrine hormones affect the same cell that releases them, binding to receptors on the cell surface.

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    Description

    Learn about the chemistry of hormones, how they are released and travel through the bloodstream, and how they interact with target cells to affect cellular activity.

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