Immunity (Edexcel International A Level (IAL) Biology): Flashcards

HIV infects and destroys helper T cells, which are responsible for activating antibody-producing B cells.

True.

AIDS develops when HIV destroys enough helper T cells that the immune system can no longer fight off infections.

HIV can be transmitted from mother to child across the placenta or through breast milk.

A physical barrier is a structure like the skin that prevents pathogens from entering the body.

The blood clotting mechanism helps prevent the entry of pathogens by sealing breaks in the skin with a clot.

The harmless microorganisms living on our skin and in our gut are called skin and gut flora.

Skin and gut flora compete with pathogens for resources, limiting their numbers and ability to infect the body.

Lysozyme is an enzyme found in secretions like tears and saliva that damages bacterial cell walls, causing them to burst.

The hydrochloric acid in the stomach helps destroy many pathogens in food and drink.

A vector is a living organism, such as an insect, that carries and transmits pathogens between hosts.

Pathogens can enter the body through breaks in the skin, which provides a direct route into the bloodstream.

True.

Pathogens can be transmitted via inhalation of droplets from infected individuals, entering through the respiratory tract.

Direct contact transmission involves physical contact between individuals, while indirect contact occurs through touching contaminated objects or surfaces.

Diseases such as malaria and yellow fever are often transmitted by vectors, which are living organisms that carry pathogens between hosts.

Inoculation is when a pathogen enters through broken skin, providing a direct route into the bloodstream.

A non-specific immune response is the part of the immune system that acts the same way to any pathogen that invades the body, regardless of its type.

The non-specific immune response is the same for any pathogen, while the specific immune response targets particular pathogens based on their unique antigens.

An antigen is a molecule, often a protein or glycoprotein, found on the surface of cells that acts as an ID tag, allowing the immune system to recognize cells as self or non-self.

Mast cells release histamine in response to tissue damage.

Inflammation is a non-specific immune response in which an area around a wound becomes swollen, warm, and painful due to increased blood flow and fluid leakage from capillaries.

Cells infected by viruses produce interferons, which are anti-viral proteins that help prevent viruses from spreading.

True.

Phagocytes use enzymes from lysosomes to digest pathogens inside the phagocytic vacuole.

Phagocytosis is the process by which phagocytes engulf and digest pathogens or dead cells.

Phagocytes become antigen presenting cells after presenting pathogen antigens on their surface, helping to initiate the specific immune response.

Histamine makes capillary walls more permeable, allowing fluid and white blood cells to enter the tissues and cause swelling.

The recognition of non-self antigens on pathogens as non-self allows the immune system to identify them as not belonging to the body.

An antigen is a marker molecule found on the surface of cells, bacteria, or viruses, which allows cell-to-cell recognition.

Antigens produced by the organism’s own body cells are called self antigens and do not stimulate an immune response.

Antigens not produced by the organism’s own body cells are known as non-self antigens and stimulate an immune response.

An antigen presenting cell displays pathogen antigens on its surface to activate the specific immune response.

An antibody is a Y-shaped protein produced by plasma cells that binds specifically to an antigen.

Antibodies are secreted by specialised white blood cells called plasma cells.

The variable region of an antibody has a unique amino acid sequence and forms the antigen binding site, giving the antibody its specificity.

True.

Antibodies can act as anti-toxins and block pathogen receptors, neutralising toxins and preventing infection of host cells.

A lymphocyte is a type of white blood cell that plays a key role in the specific immune response.

The two main types of lymphocytes are T cells and B cells.

False.

T cells are produced in the bone marrow but mature in the thymus.

T cells have specific cell surface receptors called T cell receptors, which have a similar structure to antibodies.

An antigen-presenting cell is a cell that displays foreign antigens on its surface to help activate T cells.

T killer cells bind to and destroy infected cells displaying the specific antigen.

T helper cells release chemical signalling molecules called cytokines to activate B cells and T killer cells.

B cells mature in the bone marrow, and have antibody receptors on their surface, which are actually antibodies.

An antigen-antibody complex is formed when an antibody binds specifically to its antigen.

The two main types of B cells are plasma cells (effector cells) and memory cells.

During a primary immune response, B cells divide by mitosis to form plasma cells and memory cells.

T memory cells remain in the body long after an infection and allow a faster, stronger secondary response, rapidly dividing to form T killer cells if the same antigen is encountered again.

The primary immune response is the first response of the immune system when it encounters a new antigen, involving a non-specific and then a specific immune response.

During the primary immune response, the numbers of T and B cells with the correct membrane receptors are low in the blood, so it takes time for the immune system to react.

A person experiences symptoms the first time they are infected because it takes several days for plasma cells to develop and start producing antibodies, allowing the pathogen to cause symptoms before the immune response is effective.

Memory cells are long-lived T and B lymphocytes produced during the primary immune response that remain in the blood and enable a faster, stronger immune response if the same antigen is encountered again.

False.

The secondary immune response is much faster and stronger than the primary response due to the presence of memory cells.

Antibodies are produced more quickly and in larger quantities during a secondary immune response compared to a primary response.

Active immunity is when the body’s immune system is activated by an antigen and produces its own antibodies and memory cells, resulting in long-term immunity.

Natural active immunity is gained through exposure to pathogens, while artificial active immunity is gained through vaccination. Both result in the production of memory cells and long-term immunity.

Passive immunity is when a person receives antibodies from another source without their own immune system being activated; no memory cells are produced and immunity is short-term.

Vaccines contain antigens that trigger the immune system to produce memory cells, so when the same pathogen is encountered again, a faster and stronger secondary immune response occurs, usually preventing symptoms.

An evolutionary arms race is the ongoing process where hosts and pathogens continuously evolve new adaptations to gain an advantage over each other.

It is called an evolutionary race because both pathogens and hosts continually evolve new ways to outcompete each other, with hosts developing better immune defenses and pathogens evolving new evasion strategies.

Pathogens have evolved different ways of evading their host's immune system, supporting the idea of an evolutionary arms race.

HIV kills helper T cells after infection, reducing the number of cells available to detect the virus and activate antibody production.

HIV can evade the immune system by showing antigenic variability due to its high mutation rate, resulting in new strains that require a new primary immune response.

Mycobacterium tuberculosis produces substances that prevent lysosome fusion with the phagocytic vacuole, so it is not broken down by digestive enzymes and can multiply within the phagocyte.

HIV prevents infected cells from presenting their antigens on the cell surface membrane, making it difficult for white blood cells to recognise and destroy the infected cells.

True.

Both pathogens can disrupt antigen presentation in infected cells, making it harder for the immune system to recognise and destroy them.