Edexcel International A Level Biology - Immunity
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Questions and Answers

What characterizes infectious diseases?

  • They usually show no signs or symptoms.
  • They are exclusively viral in nature.
  • They are caused by pathogens. (correct)
  • They cannot be transmitted between individuals.

    • Which of the following is NOT considered a pathogen?

  • Fungi
  • Non-pathogenic viruses (correct)
  • Bacteria
  • Viruses

    • Which of these statements about tuberculosis is true?

  • It is solely a mental health disorder.
  • It is caused by a specific type of bacteria. (correct)
  • It cannot affect the respiratory system.
  • It is transmitted via direct contact only.

    • What term describes the ability of pathogens to be spread within a population!

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

    Which of the following correctly explains the relationship between pathogens and diseases?

    <p>Pathogens can lead to diseases but are not synonymous with them.</p> Signup and view all the answers

    What is the main purpose of a vaccine?

    <p>To induce artificial active immunity through the introduction of antigens</p> Signup and view all the answers

    How does vaccination lead to long-term immunity?

    <p>It stimulates the production of memory cells that recognize antigens</p> Signup and view all the answers

    What factor necessitates the modification of vaccinations?

    <p>Antigenic variation due to mutation of pathogens</p> Signup and view all the answers

    What forms can a vaccine's antigens take?

    <p>Either killed or weakened pathogens, or antigens alone</p> Signup and view all the answers

    What is a primary reason vaccinated individuals do not usually show disease symptoms?

    <p>Memory cells are able to initiate a faster immune response upon re-exposure</p> Signup and view all the answers

    What role does the blood clotting mechanism play in relation to pathogen entry?

    <p>It plays an important role in preventing pathogen entry after skin damage.</p> Signup and view all the answers

    How do harmless microorganisms in the gut and skin help protect the body?

    <p>They compete with pathogens for resources, limiting their numbers.</p> Signup and view all the answers

    What is the primary function of hydrochloric acid in the stomach?

    <p>To create an acidic environment that is unfavourable to many pathogens.</p> Signup and view all the answers

    What effect does the enzyme lysozyme have on bacterial cells?

    <p>It damages bacterial cell walls, causing them to burst.</p> Signup and view all the answers

    What happens to pathogens when the skin is damaged?

    <p>Some may enter before a blood clot forms due to exposed tissue.</p> Signup and view all the answers

    Which virus is classified as a retrovirus containing RNA?

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

    What is the main type of cell that HIV infects in the human body?

    <p>Helper T cells</p> Signup and view all the answers

    How does HIV enter helper T cells?

    <p>By attaching to a receptor molecule</p> Signup and view all the answers

    What occurs after the viral RNA is released inside the helper T cell?

    <p>It is used as a template to produce DNA</p> Signup and view all the answers

    What stage follows the acute HIV syndrome stage after the initial infection?

    <p>Asymptomatic or chronic stage</p> Signup and view all the answers

    What is the primary consequence of the reduction in helper T cells due to HIV infection?

    <p>Decreased ability to fight infections</p> Signup and view all the answers

    How does a mother transmit HIV to her child during birth?

    <p>By mixing blood during delivery</p> Signup and view all the answers

    At what stage is an individual classified as having advanced AIDS?

    <p>When the immune system is severely compromised</p> Signup and view all the answers

    What is the typical cause of death for individuals with advanced AIDS?

    <p>Opportunistic infections</p> Signup and view all the answers

    Which of the following factors does NOT affect the progression of HIV into AIDS?

    <p>Type of diet</p> Signup and view all the answers

    Which statement accurately distinguishes between HIV and AIDS?

    <p>HIV is a virus and AIDS is the disease caused by HIV.</p> Signup and view all the answers

    How can pathogens commonly enter the body?

    <p>Through body openings and breaks in the skin</p> Signup and view all the answers

    What role do vectors play in the transmission of pathogens?

    <p>They carry and transmit pathogens between hosts.</p> Signup and view all the answers

    What is a primary method of pathogen entry via ingestion?

    <p>Eating undercooked food or contaminated drinks</p> Signup and view all the answers

    Which disease is commonly associated with inhalation of airborne pathogens?

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

    Which method is NOT a typical route for pathogen entry into the host?

    <p>Transfusion of untainted blood</p> Signup and view all the answers

    What are antigens found on?

    <p>Cell surface membranes and bacterial cell walls</p> Signup and view all the answers

    What are self antigens known for?

    <p>Being produced by the organism's own body cells</p> Signup and view all the answers

    What role do antigen presenting cells play in the immune response?

    <p>They transfer antigens to lymphocytes</p> Signup and view all the answers

    What is the structure of antibodies?

    <p>Y-shaped molecules consisting of heavy and light chains</p> Signup and view all the answers

    What is unique about the variable region of an antibody?

    <p>It allows for binding to antigens, giving specificity</p> Signup and view all the answers

    The flexibility of an antibody molecule is primarily due to which region?

    <p>Hinge region</p> Signup and view all the answers

    Which cells are responsible for producing antibodies?

    <p>Plasma cells</p> Signup and view all the answers

    Which class of antibodies has a constant region that does not vary within the class?

    <p>All antibody classes</p> Signup and view all the answers

    What triggers the specific immune response?

    <p>The binding of lymphocytes to non-self antigens</p> Signup and view all the answers

    Which of the following correctly describes an antigen?

    <p>It activates the immune response when recognized as non-self</p> Signup and view all the answers

    Study Notes

    Edexcel International A Level Biology - Immunity

    • Immunity is the body's ability to fight off infections and diseases.

    • Tuberculosis (TB) is a bacterial disease caused by Mycobacterium tuberculosis.

    • Transmission occurs through droplets released when infected people cough or sneeze.

    • The bacteria are engulfed by phagocytes, but can sometimes survive and reproduce.

    • A healthy immune system can prevent TB at the primary infection stage, but it can become active later.

    • HIV (Human Immunodeficiency Virus) is a retrovirus.

    • Transmission occurs through bodily fluids (sexual contact, blood transfusions, sharing needles, mother-to-child).

    • HIV infects helper T cells (CD4 T-lymphocytes), which are crucial for the immune response.

    • The virus replicates within the helper T cell, which then burst.

    • The initial stage (acute HIV syndrome) has flu-like symptoms, then a chronic stage without symptoms.

    • Later (symptomatic stage), HIV symptoms arise.

    • Pathogens: Routes of Entry

    • Pathogens enter the body through various routes:

      • Body openings (mouth, eyes, urinary tract).
      • Breaks in the skin.

    • Vectors are living organisms that carry pathogens and transmit them between hosts (e.g., insects like mosquitoes).

    • Inhalation Exposure to pathogens through droplets released via coughs, sneezes, or talking.

    • Ingestion Pathogens entering the body through contaminated food or drink.

    • Indirect contact Pathogens transfer between hosts via inanimate objects like bedding or surfaces.

    • Direct contact Transmission through direct skin-to-skin contact or bodily fluid exchange.

    • Inoculation Pathogens enter through breaks in the skin via bites, scratches, or injections.

    • Non-Specific Immune Responses

    • The immune system has non-specific and specific responses.

    • Non-specific responses are the body's initial reaction to any pathogen (e.g., inflammation, interferons, phagocytosis).

    • Inflammation is the body's response to tissue damage to trap pathogens and stop infection.

    • Interferons are proteins produced by virus-infected cells that stop viruses from spreading to other cells.

    • Phagocytosis is a process where phagocytes engulf and destroy pathogens.

    • Specific Immune Responses

    • Antigens are molecules, proteins or glycoproteins on a cell's surface that identify 'self' and 'non-self' cells.

    • Specific responses are directed against particular pathogens.

    • Lymphocytes (T cells and B cells) are crucial to the specific immune response.

    • T cells help to activate B cells and kill infected cells.

    • B cells produce antibodies specific to antigens, and become plasma cells which release antibodies.

    • Antibodies are Y-shaped proteins that bind to specific antigens on pathogens, marking them for destruction.

    • Developing Immunity

    • The first exposure to a pathogen (primary response) is slower as the body identifies and activates the appropriate immune responses.

    • After the primary response, there are memory cells and the body retains immunity against the pathogen (secondary response) to reduce infection time and severity.

    • Active immunity. Antibodies are produced by the body through exposure to antigen (natural/artificial). Memory cells are formed, resulting in long-term immunity.

    • Passive immunity. Antibodies are received from another source, rather than produced by the body. No memory cells are formed, resulting in temporary immunity.

    • Pathogens vs Hosts: An Evolutionary Race

    • Host organisms (e.g., humans) evolve immune systems to combat pathogens.

    • Pathogens evolve mechanisms to evade host immunity (e.g., antigenic variation, avoiding immune detection).

    • This co-evolutionary process is considered an evolutionary arms race.

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    Edexcel International A Level Biology PDF

    Description

    Test your knowledge on immunity, focusing on tuberculosis and HIV. This quiz covers how the immune system functions, how these pathogens spread, and the stages of infection. Ideal for students studying Edexcel International A Level Biology.

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