Practice SAC Flashcards
Why are viruses considered to be non-cellular? (1 mark)
- Have no cell structure 1/2
- Cannot metabolise energy or reproduce outside of host cell 1/2
Example of microbiota (first line of defence)
- Gut flora in digestive system
Identify what the first and second line are collectively known as, and explain the characteristic that lead them to be classed this way (2 marks)
- innate or non-specific immunity 1
- Because it does not distinguish between pathogens and will behave the exact same way regardless of pathogen 1
What are the four stages of phagocytosis (4 marks)
- engulfment (endocytosis) 1
- formation of bacteria engulfed in vesicle (phagosome) 1
- lysosomes attaching to phagosome to digest bacteria (phagolysosome) 1
- expulsion of undigested contents (exocytosis) 1
Which line of defence do natural killer cells belong to? (1 mark)
Second line 1
How are natural killer cells able to recognise body cells infected with viruses?
- can recognise cells that do not contain self -markers, or inhibited MHC 1 cells that are no longer making MHC 1 proteins
How do natural killer cells destroy virally infected cells? (2 marks)
- natural killer cells induce apoptosis 1
- release performing which punch holes in the plasma membrane, and undergo degranulation to release granzymes into cell 1
Which lymphocyte is stimulated by the interferons released by an infected virus cell?
T lymphocytes or cytotoxic T cells
Where do T cells originate and mature? (1 mark)
- originate in bone marrow 1/2
- mature in thymus 1/2
Where do b cells originate and mature? (1 mark)
- originate in bone marrow 1/2
- mature in spleen/bone marrow 1/2
Explain the difference between a lymphocyte and a leukocyte
- leukocyte is all WBC
- lymphocyte is WBC specific to the lymphatic system
If swelling occurs in the groin or under someone’s arms, identify the specific site of swelling and what occurred to result in swelling (2 marks)
- lymph nodes 1
- initiated by activation of lymphocytes which undergo clonal expansion to produce many more at that location 1
Which line of defence is associated with lymphocytes, define the characteristics (2 marks)
- third line of defence 1/2
- adaptive and specific 1/2
- initiates specific responses to specific pathogens 1
What level of protein are antibodies classed as?
Quaternary
Describe the process of clonal expansion (2 marks)
- a naive B lymphocyte encounters a complementary shaped antigen to its B cells receptor/antibody and a helper T cells binds
-releases cytokines and initiates clonal expansion
Outline the steps of the humoral response that occur after clonal selection has taken place (4 marks)
- clones of b lymphocytes are activated by helper T cytokines 1
- then proliferate and differentiate into memory and plasma b cells
- plasma b release antibodies from their surface
- memory b cells circulate in the lymphatic system for future exposure to the same antigen.
There is a lymphocyte involved in both humoral and cell mediated adaptive immune response (2 marks)
- T helper cell 1
- binds to antigen on APC and releases cytokines which activate B cells and cytotoxic T cells 1
Outline the main step in activating cytotoxic T cells
- Phagocyte engulfs a pathogen and uses a fragment on their MHC 2 markers
- Helper T cell binds to mhc 2 marker of complementary shape
- Helper T cell releases cytokines to initiate clonal expansion
- T lymphocytes proliferates and differentiates into cytotoxic T cells and memory cells
Explain what will happen when a cytotoxic T cell encounters a virally infected cell
- cytotoxic T cell binds to antigen complementary to its receptor
- releases perforin and granzymes that induce apoptosis in the infected cell
What does contagious mean?
Means that it is easily spread from person to person
Does contagious mean the same thing as infectious?
- No, not all contagious diseases are infectious. Contagious diseases are easily spread from one individual to another, while infectious diseases are caused by pathogens
What is the period of time between a person being exposed to a pathogen and the symptoms of that pathogen being shown?
Incubation period
What is the period of time between a person being exposed to a pathogen and the symptoms of that pathogen being shown?
Incubation period
Explain what a vaccine is
An injection of a dead or weakened antigen or pathogen that initiates an immune response
For some viruses, it is recommended for people to have two doses of the vaccine. Explain why this second dose is recommended for full vaccination (2 marks)
Sometimes the initial response of the body to a weakened or dead pathogen is quite weak, so a second exposure is needed to produce a rapid secondary antibody response which is larger than the primary response
What type of immunity is a vaccine, and why?
- Artificial active
- body makes its own antibodies, however they do not have to come in contact with pathogen
What is meant by herd immunity, and why is it important for a population (2 marks)
- when a large proportion of a population is immunised against a disease
- important for babies and immune compromised people who are unable toe to receive the vaccine
Name 3 social strategies that the government could use to try and limit the spread of a contagious disease
- increased hygiene, masks, social distancing, hand washing
If there were an outbreak of a virus in a country, what is a scientific strategy that could be used by scientists?
- develop an antiviral drug for the virus, or a more potent vaccine
What does it mean to be pathogenic? (1 mark)
- has the ability to interfere with the normal functioning body and cause disease
How can a disease be deemed as non-infectious? Provide an example (2 marks)
- Many diseases can be caused by genetic mutations or environmental influences, and are not infectious.
- examples include cancer, scurvy
What are 3 non cellular pathogens
Prions, viruses, viroids
What are 4 cellular pathogens
Bacteria, parasites, fungi, protozoans
Identify the self-antigen that is present on all nucleated body cells
MHC 1 marker
Which white blood cell is most likely to be first to a site of infection?
Neutrophils
Describe the two actions a neutrophil undergoes when in contact with a virus
- undergo phagocytosis
- release cytokines to signal other immune cells to the site
If a MHC 1 marker is removed from a virally infected cell, which cells from the innate immune system would recognise the virally infected cell, and how does it assist in eliminating the virus from the body? (2 marks)
- natural killer cells
- induce apoptosis by releasing perforin to punch holes in the cell membrane, and undergo degranulation to release granzymes into the cell
Identify two roles of the lymphatic system
- return fluid to blood, filter tissue fluid, site of antigen recognition, site of lymphocyte maturation
Identify and discuss a role that antibodies play in helping to destroy pathogens when they have been released from plasma cells
- opsonisation - antibodies bind to antigens flagging them for destruction by phagocytes
- agglutination - antibodies bind to two different antigen’s forming a clump, which immobilises them to prevent spread of infection and makes the m more susceptible to phagocytosis
Explain how an emerging disease is different to a re emerging disease (2 marks)
- emerging disease is a disease that was previously unknown or recognition. Can also be a known pathogen in a new location
- re emerging diseases is a disease that has caused problems in the past, but has been diminished through vaccination programs and treatments, but can fare up to epidemic levels t those who don’t have immunity to the disease
Identify the part of the adaptive immune response that enables people to acquire immunity and explain what happens if that person is exposed to the same pathogen again.
- individual has acquired memory cells when they fought off a pathogen the first time, which provide immunological immunity
- if the same person encounters the virus again, those memory cells will differentiate and clone into effector cells and fight off the virus in a shorter amount of time
Would a pregnant woman be able to provide protection to her unborn child if she is infected with a virus
Yes, if she is actively producing antibodies, then the antibodies could pass through the placental wall into the blood of the baby, which would provide the baby with passive natural immunity
Define the term pathogen
A causative agent of disease
Describe how a virus infects a cell and replicates (2 marks)
- virus injects its genetic material into a host cell
- virus then uses the cell machinery to replicate its genetic material
Discuss one barrier to infection employed by plants
- wavy leaves, thick bark prevent pathogen entry
- citronella, cafffiene deter or kill insects/pathogens
Explain what innate and non-specific mean (2 marks)
- innate means the organism is born with it
- non specific means it does not distinguish between pathogens and will behave the exact same regardless of the pathogen and if it’s been encountered before
What does environmental resistance mean and why does it make a virus difficult to control
- virus can live outside host cells for a long time
- easily spread and difficult to control
Discuss the key roles of the second line of defence cells involved in the inflammatory response (4 marks)
- injured cells at site of wound release cytokines attracting neutrophils which engulf the pathogens
- mast cells release histamine, increasing blood vessel permeability and dilation allowing more leukocytes to enter
- macrophages engulf pathogens via phagocytosis
- results in pain, redness and swelling
Explain how a fever can work to combat invading pathogens
Raising the temperature provide unfavourable conditions for pathogens (denaturation may occur)
Outline the stages of the humoral response from activation to destruction of the pathogen
- a macrophage/dendritic cell engulfs a pathogen during phagocytosis and presents the antigen on its MHC 2 marker. Then transported to the lymph nodes via the lymphatic system
- APC presents antigen to helper T cell of complementary receptor, releasing cytokines that select a naive B cell to undergo clonal expansion into memory or plasma b cells
- memory b cell provide memory in case of reinfection
- plasma b cells release antibodies that can agglutinate and neutralise pathogens
Outline the stages of the cell mediated response from activation to destruction of virally infected cells
- a macrophage/dendritic cell engulfs a pathogen during phagocytosis and presents the antigen on its MHC 2 marker. Then transported to lymph nodes via lymphatic system
- APC presents antigen to a helper T cell with complementary receptor, releasing cytokines that select a naive T cell to undergo clonal expansion into memory and cytotoxic T cells
- memory cells provide memory in case of reinfection
Cytotoxic T cells release granzymes and perforin to initiate apoptosis in infected cells
Identify the cells involved in the allergic response and explain their role in an allergic reaction (2 marks)
Allergies occur to the overproduction of IgE antibodies, they then bind to the surface of mast cells and form cross links easily when allergen is encountered. Mast cells release histamine and cause inflammation
