OCR A Level Biology 4.1: Diseases and Pathogens
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Questions and Answers

What is the term for the long-term protection mechanism that plants activate against pathogens?

  • Cellular defense
  • Pathogen response system
  • Chemical immunity
  • Systemic acquired resistance (correct)

    • Ethylene helps plants communicate by suppressing defense mechanisms in other parts of the plant.

    False

    Name one example of a physical defense mechanism that vertebrate animals use against pathogens.

    Skin

    ___ is a signaling compound secreted by plants that helps them respond to pathogen attacks.

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

    Match the following types of immune responses with their descriptions:

    <p>Physical = Body tissues that act as barriers to pathogens Cellular = Cells that detect and signal the presence of pathogens Chemical = Substances that create inhospitable environments for pathogens</p> Signup and view all the answers

    What is a key factor that can reduce the likelihood of disease transmission in a population?

    <p>High number of immune or resistant individuals</p> Signup and view all the answers

    Individuals who are resistant to a disease will never show symptoms upon exposure to the pathogen.

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

    What genetic trait gives individuals resistance to malaria?

    <p>Heterozygous for the sickle cell allele</p> Signup and view all the answers

    Individuals who have previously been infected with a pathogen develop _____ against that pathogen.

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

    Match the terms related to disease resistance with their definitions:

    <p>Resistance = Genetic mechanisms that prevent infection Immunity = Reaction to a previous infection Susceptibility = Vulnerability to pathogens Pathogen = Organism that causes disease</p> Signup and view all the answers

    What is antigenic drift?

    <p>Small changes in the structure and shape of antigens over time</p> Signup and view all the answers

    Antigenic shift refers to small changes in the antigens of a pathogen.

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

    What are two ways that pathogens can hide from the immune system?

    <p>Living inside cells, coating their bodies in host proteins</p> Signup and view all the answers

    Eukaryotic diseases, like ______, display many antigens on their cell surface membranes, complicating vaccine development.

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

    Match the method of antigenic variation with its description:

    <p>Antigenic drift = Small gradual changes in antigens Antigenic shift = Major changes in antigens Antigenic concealment = Hiding from the immune system Antigenic variation = Any change in the antigens of a pathogen</p> Signup and view all the answers

    What can result from cross-breeding in viruses?

    <p>The production of new strains with mixed antigens</p> Signup and view all the answers

    Herd immunity protects only those who have been vaccinated.

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

    What outbreak occurred in Swansea in 2012 due to low vaccination uptake?

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

    Which of the following is a reason why some diseases have not been eradicated despite the availability of vaccines?

    <p>Insufficient vaccination coverage in the community.</p> Signup and view all the answers

    Live attenuated vaccines can be suitable for individuals with weakened immune systems.

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

    Ring immunity involves vaccinating people living or working near a ________ individual.

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

    What is a primary goal of the World Health Organisation (WHO) regarding influenza?

    <p>To provide information about likely spreading strains</p> Signup and view all the answers

    Name an example of a live attenuated vaccine.

    <p>MMR (Measles, Mumps, and Rubella)</p> Signup and view all the answers

    Inactivated vaccines contain pathogens that have been ______.

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

    Cross-breeding of influenza viruses is believed to increase immunity in the population.

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

    What proportion of the population needs to be vaccinated to achieve herd immunity varies by ________.

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

    What is a characteristic of inactivated vaccines compared to live attenuated vaccines?

    <p>They cannot cause disease even in immunocompromised individuals.</p> Signup and view all the answers

    Match the following terms with their correct definitions:

    <p>Herd immunity = Protection of non-immunised individuals when a large proportion is vaccinated Ring immunity = Vaccination of people near an infected individual to prevent disease spread Cross-breeding = The process by which virus strains exchange antigens Pandemic = Widespread outbreak of a disease affecting a large number of people globally</p> Signup and view all the answers

    Political instability can hinder efforts to eradicate infectious diseases.

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

    What is one challenge faced in eradicating diseases aside from vaccine availability?

    <p>Lack of public health facilities or unstable political situations</p> Signup and view all the answers

    Match the type of vaccine with its description.

    <p>Live attenuated vaccines = Contain weakened pathogens that trigger a strong immune response Inactivated vaccines = Contain killed pathogens or subunits that are safer for immunocompromised individuals Booster doses = Required for inactivated vaccines to enhance immunity Adjuvants = Substances that enhance the immune response to vaccines</p> Signup and view all the answers

    What is the primary method of transmission for Late blight in potatoes?

    <p>Spores carried by wind</p> Signup and view all the answers

    All fungal diseases are less serious for plants than animals.

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

    What initial symptoms indicate the presence of potato blight?

    <p>Small, dark brown marks on the leaves</p> Signup and view all the answers

    Black Sigatoka primarily affects ______ plants

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

    Match the following pathogens with their respective diseases:

    <p>Bacterium = Ring rot Virus = Tobacco mosaic Protoctist = Malaria Fungus = Athlete's foot</p> Signup and view all the answers

    Which of the following is a characteristic of fungi?

    <p>They consist of filaments known as hyphae.</p> Signup and view all the answers

    The lack of photosynthesis in banana plants due to Black Sigatoka can eventually cause the whole leaf to die.

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

    Name one way fungi can spread.

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

    Athlete's foot is transmitted through ______ contact.

    <p>skin-to-skin</p> Signup and view all the answers

    Which pathogen causes potato blight?

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

    Study Notes

    OCR A Level Biology 4.1

    • Communicable diseases are caused by pathogens that can be transmitted between individuals.
    • Non-infectious diseases are not caused by pathogens. Examples include lung cancer, cardiovascular disease, and depression.
    • Pathogens include bacteria, viruses, fungi, and protoctists.
    • Bacteria are prokaryotic organisms. Some are non-pathogenic, while others are pathogenic. Pathogenic bacteria can remain in body cavities (eg. M. tuberculosis).
    • Viruses have no cellular structure and rely on host cells to replicate. TMV (tobacco mosaic virus) infects plants, causing yellowing leaves. Influenza viruses cause the flu (influenza A, B, and C). HIV (human immunodeficiency virus) is an enveloped retrovirus.
    • Protoctists are unicellular eukaryotes. Plasmodium falciparum is a protist that causes malaria. P. infestans causes potato blight.
    • Fungi have cell walls and reproduce via hyphae. They cause diseases like athletes foot and ring rot in plants (potatoes, tomatoes). Black Sigatoka affects bananas.
    • Transmission of pathogens can occur through physical contact, vectors (e.g., mosquitoes for malaria), airborne droplets (e.g., influenza), or contaminated surfaces (e.g., contaminated food).
    • Disease transmission is the transfer of pathogens from an infected host to an uninfected host.
    • Transmission by a vector involves an organism that transfers a pathogen to an uninfected individual. Vectors, such as mosquitoes, can carry pathogens without being harmed themselves, increasing the likelihood of transmission.
    • Factors affecting transmission include population density, living conditions (crowded housing, sanitation facilities, water treatment facilities), and human behaviours.
    • Resistance to diseases and susceptibility levels are related to genetic factors and environmental factors.
    • Vaccination relies on intentionally introducing an antigen to stimulate the immune response.

    Plant Defences

    • Plants use both passive and active mechanisms to defend against pathogens.
    • Passive defences are always present. Examples include a waxy cuticle, cellulose cell walls, and the Casparian strip.
    • Active defences are triggered by pathogen invasion. This includes responses like the production of callose and lignin, and the narrowing of plasmodesmata (channels connecting plant cells).
    • Chemical defences are also employed, such as the production of toxic compounds (catechol) and sticky resins in bark to trap pathogens. Microorganisms that are naturally present can compete against harmful pathogens.
    • Ethylene is a signalling compound allowing communication between plants to stimulate other parts of the plant to prepare defenses against infections.

    Non-specific Immune Response

    • Skin and mucous membranes provide the first line of defense, acting as physical barriers.
    • Chemical secretions like lysozymes and hydrochloric acid create an inhospitable environment for pathogens.
    • Commensal microorganisms compete with pathogens for resources.
    • Expulsive reflexes like coughing and sneezing remove pathogens.

    Specific Immune Response: T Lymphocytes

    • T-lymphocytes (T cells) mature in the thymus gland.
    • They have specific T cell receptors (TCRs) that recognize antigens, triggering clonal selection and expansion.
    • T cells differentiate into helper T cells, killer T cells and memory T cells.

    Specific Immune Response: B Lymphocytes

    • B-lymphocytes (B cells) mature in the bone marrow.
    • They produce antibody receptors (BCRs) that recognize specific antigens, triggering clonal selection and expansion.
    • Activated B cells differentiate into plasma cells and memory B cells.

    Antibody Structure and Function

    • Antibodies (immunoglobulins) are Y-shaped proteins with heavy and light chains.
    • The variable region of the antibody is unique to each antigen, allowing for specific binding.
    • Antibodies act as opsonins, agglutinins, and anti-toxins, facilitating pathogen destruction.

    Primary & Secondary Immune Responses

    • Primary response is slower, requiring time for clonal selection and antibody production after first exposure to an antigen.
    • Secondary response is much faster and stronger due to memory cells, which have a faster response time and antibody production.

    Types of Immunity

    • Active Immunity is acquired either naturally (exposure to a pathogen) or artificially (vaccination). It results in the production of memory cells, that enables the body to respond faster during subsequent exposures.
    • Passive Immunity is acquired without an immune response. Antibodies from another organism (e.g. mother's breast milk) are received. Passive immunity doesn't trigger memory cells and provides only short-term protection.

    Autoimmune Diseases

    • Autoimmune diseases occur when the body's immune system attacks its own tissues.
    • These diseases can affect a single organ or the entire body. Rheumatoid arthritis affects joints.

    Vaccination

    • Vaccination is an artificial way to gain active immunity.
    • It involves introducing an antigen to stimulate an immune response without causing disease.
    • Vaccines can be live attenuated (weakened) or inactivated (killed) pathogens, or contain specific parts of pathogens.
    • Herd immunity occurs when a large percentage of the population is vaccinated, providing protection for those who cannot be vaccinated.

    Antibiotics

    • Antibiotics are chemical substances used to treat bacterial infections.
    • They are either bactericidal (killing bacteria) or bacteriostatic (inhibiting bacterial growth).
    • Antibiotics can have broad-spectrum effects or be more targeted towards specific bacteria.
    • Antibiotic resistance arises when bacteria evolve resistance genes, often through mutation.

    Sources of Medicine

    • New drugs are often discovered by studying the natural world, e.g., by examining the genomes of microbes and analyzing compounds from plants and animals.
    • Identifying molecules that target pathogens or enzymes involved in disease processes plays a role in drug discovery.
    • Modifying existing drugs to improve their effectiveness is another approach.
    • Personalized medicine aims to tailor treatments to individual genetic characteristics.

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    OCR A Level Biology Past Paper PDF

    Description

    Test your knowledge on communicable and non-infectious diseases in OCR A Level Biology. This quiz covers various pathogens, including bacteria, viruses, fungi, and protoctists, as well as their effects on health. Discover the intricacies of how these diseases manifest and their impact on organisms.

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