Defence Against Disease (DP IB Biology)

The skin acts as a tough physical barrier that prevents the entry of pathogens into the body.

Sebum, produced by the sebaceous glands, maintains a low skin pH, which inhibits the growth of microorganisms.

Mucous membranes line vulnerable areas and produce mucus that traps microorganisms, which are then removed from the body to prevent infection.

Cilia sweep mucus, along with trapped microorganisms, upwards to be swallowed or expelled, preventing infection.

Goblet cells in the respiratory tract produce mucus.

Lysozyme enzymes are found in mucus and have antibacterial properties, providing additional protection from invading microorganisms.

When the skin is cut, platelets form a temporary plug and release clotting factors that trigger a chemical cascade, leading to blood clotting.

Platelets are cellular fragments that help stem bleeding by forming a temporary plug and releasing clotting factors that initiate the clotting process.

They also get trapped in fibrin along with blood cells, which then hardens to become a scab.

Clotting factors stimulate the release of the enzyme thrombin.

Thrombin catalyses the conversion of the soluble protein fibrinogen into insoluble fibrin, which forms a mesh to trap platelets and blood cells, sealing the wound.

Exposure to air causes the fibrin mesh to harden, forming a scab that seals the wound and prevents the entry of microorganisms.

The innate immune system recognizes and responds to any non-self antigens, such as bacteria, viruses, and allergens, using a broad, non-specific immune response.

The innate immune system recognises non-self antigens on foreign cells, triggering an immune response, while self antigens on the body’s own cells prevent an immune response.

Phagocytes in the innate immune system engulf and digest any item that displays non-self antigens, forming part of the non-specific immune response.

False.

The adaptive immune system does change, the innate immune system does not.

The adaptive immune system targets specific non-self antigens, produces antibodies, and creates immunological memory, allowing for a faster and more effective response upon subsequent exposures to the same pathogen.

Immunological memory is the ability of the adaptive immune system to remember specific pathogens, leading to a faster and stronger immune response upon future exposure to the same pathogen.

True.

Vaccination makes use of the adaptive immune system.

False.

Phagocytes are responsible for a non-specific immune response.

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

A lymphocyte is a type of white blood cell involved in the specific immune response.

True.

B cells mature in the bone marrow.

T cell receptors are specific proteins on the surface of T cells that bind to particular antigens.

An antigen-antibody complex is formed when a B cell antibody receptor binds to its specific antigen.

True.

Memory cells allow for a faster immune response to the same pathogen in the future.

When a T cell binds to an antigen, it becomes activated and divides by mitosis to produce clones.

Plasma cells produce specific antibodies to combat non-self antigens.

An antigen is a molecule on the cell surface membrane that triggers an immune response.

True.

The immune system can distinguish between 'self' and 'non-self' based on cell surface molecules.

Non-self antigens on the surface of microorganisms or other foreign cells trigger an immune response.

True.

Blood type is determined by the presence of specific antigens on the surface of red blood cells.

The two antigen markers important in blood transfusions are the ABO marker and the Rhesus (Rh) marker.

If a transfusion is given with a mismatched blood type, the antigens on the red blood cells will trigger an immune response.

Agglutination is the clumping together of particles such as red blood cells and pathogens due to the binding of antigens and antibodies.

True.

T-helper cells have specific receptors that bind to antigens.

An antigen-presenting cell is a cell that displays non-self antigens on its surface membrane after engulfing a pathogen.

Clonal expansion is the process by which an activated B-cell divides by mitosis to produce many identical clones.

True.

Plasma cells are the mature B cells that produce antibodies.

False.

B cells are activated by T-helper cells that have been activated by binding to antigens.

After activation, B cells divide by mitosis to create clones, some of which become plasma cells that produce antibodies, and others become memory cells.

Memory cells provide long-lasting immunity by quickly responding to a previously encountered pathogen during a secondary immune response.

A primary immune response is the body's initial response to a specific antigen, leading to the production of antibodies and memory cells.

The secondary immune response is triggered when the same antigen enters the body a second time, activating memory cells.

False.

The secondary immune response is much faster and larger than the primary immune response.

Plasma cells produce antibodies that are specific to the target antigen.

False.

HIV cannot survive outside the human body; it needs host cells to replicate.

HIV is transmitted through the direct exchange of body fluids, such as during sexual intercourse, blood donation, sharing needles, and from mother to child.

A retrovirus is a type of virus, like HIV, that uses the enzyme reverse transcriptase to produce DNA from its RNA in a host cell.

False.

HIV is not transmitted by a vector; it is spread by direct exchange of body fluids.

HIV primarily attacks T-helper cells, a type of lymphocyte involved in the immune response.

Being HIV positive means that antibodies to fight HIV have been detected in the blood.

As HIV infection progresses, the ability to produce antibodies decreases, leading to a weakened immune system and increased susceptibility to opportunistic infections.

AIDS, or acquired immune deficiency syndrome, is a condition where the immune system is severely weakened due to HIV, leading to vulnerability to multiple infections and diseases.

False.

HIV is the virus, while AIDS is the syndrome caused by the virus.

The progression of HIV to AIDS can be slowed down using anti-retroviral drugs.

Antibiotics inhibit the growth of microorganisms, particularly bacteria.

False.

Antibiotics are ineffective against viruses because viruses are non-living and lack the cellular processes that antibiotics target.

Viruses are unaffected by antibiotics because they lack metabolism and cell structure, and they replicate using the host cell's machinery.

Antibiotics do not harm eukaryotic cells because they target specific bacterial processes, like transcription and cell wall formation, that occur in prokaryotic cells but not in eukaryotic cells.

Penicillin interferes with the production of bacterial cell walls, leading to the death of the bacteria.

False.

Some bacteria, like those causing tuberculosis, have thicker cell walls or enzymes that break down penicillin, making them resistant.

Penicillin is derived from fungi in the genus Penicillium.

Antiviral drugs are medications that target viral enzymes without harming the host cell.

Antibiotics target processes such as transcription, translation, DNA replication, ribosome function, and cell wall formation.

True.

Antibiotics can be derived from living organisms or made synthetically in a laboratory.

Variation within a bacterial population is caused by mutations in DNA.

True.

Antibiotic resistance is an example of evolution by natural selection.

A bacterial population becomes resistant to antibiotics over time because resistant bacteria survive, reproduce, and pass on their resistant genes to their offspring, leading to an entire population that is resistant.

The overuse of antibiotics is problematic because it exerts selective pressure on bacteria, supporting the evolution of antibiotic resistance.

True.

MRSA is resistant to multiple antibiotics and is difficult to treat.

Measures to avoid antibiotic resistance include avoiding unnecessary antibiotic prescriptions, maintaining hygiene in hospitals, and reducing routine antibiotic use in agriculture.

Antibiotic resistance presents the challenge of making the treatment of infections more difficult and contributes to higher mortality rates.

The development of new antibiotics is important for the future to ensure the continued effectiveness in treating common infections and minor injuries.

Chemical libraries are used by researchers to identify and develop new antibiotics by screening compounds with antibacterial properties.

Zoonosis refers to diseases that can cross the species barrier from animals to humans.

False.

Zoonotic diseases can infect both animals and humans.

Zoonotic diseases are a growing concern because the close relationships between humans and animals make them difficult to control and may lead to pandemics.

Factors include the lack of necessary receptors in the species or the body temperature not being suitable for the disease's development.

True.

Some zoonotic diseases can initially emerge from animals and later develop into human-only strains, such as HIV.

True.

COVID-19 is an example of a zoonotic disease.

A vaccine is when a source of antigens or DNA/RNA which codes for antigens enters the body, mostly via an injection. They trigger an immune response and create long-term immunity by causing memory cells to be created for a pathogen.

True.

Vaccines induce immunity without causing the disease.

Herd immunity is when a large percentage of the population is vaccinated, providing protection for the entire population by reducing the places where the pathogen can breed.

A live attenuated vaccine contains weakened versions of the pathogen.

An inactivated vaccine is made from killed, non-living components of pathogens or antigens alone.

Vaccines produce long-term immunity.

True.

Smallpox was eradicated by a vaccination programme in 1980.

The primary immune response triggered by a vaccine involves T helper cells activating B plasma cells to secrete specific antibodies.

Peer review is the process where other scientists in the same field evaluate the accuracy and validity of research data and conclusions.

False.

Vaccines are tested rigorously and the risks of side effects are minimal but not nil.

A percentage difference calculation allows you to compare two directly comparable values that occur at the same time.

Percentage change is the calculation that compares two values from the same data set at different times, indicating how a factor has changed over time.

A percentage decrease occurs when the original value is larger than the new value.