B3 - Infection And Response Flashcards
What are pathogens?
Pathogens are microorganisms that cause infectious disease
What are the four types of pathogen?
Bacteria
Fungi
Protist
Virus
How do bacteria make us feel ill?
Reproduce rapidly in the body
And produce toxins that damage cells
How do viruses make us feel ill?
Live and replicate inside cells
Causing cell damage such as cell bursts
What are protists?
Single-celled eukaryotes
That are Transferred by a vector
How can pathogens be spread?
Water
Air
Direct contact
How can the spread of diseases be reduced or prevented?
Hygiene - regular hand washing before preparing food and by disinfecting surfaces
Vaccination of (make specific to question) - to provide (herd) immunity
Isolation - to reduce contact with healthy people
Destroy vectors - by using insecticides for example
What are three types of viral disease?
Measles
HIV
Tobacco mosaic virus (TMV)
What are the symptoms of measles?
Fever
Red skin rash
How is measles spread?
Inhalation of droplets from sneezes and coughs from infected people
How can the spread of measles be reduced or prevented?
Most young children are vaccinated against measles
By isolating infected people
What are the symptoms of HIV?
Initially a flu-like illness
Often no symptoms for years
If AIDS develops, recurrent infections and longer recovery
How is HIV spread?
Sexual contact
Exchange of bodily fluids such as blood when drug users share needles
How can the spread of HIV be prevented or reduced?
Antiretroviral drugs control HIV to stop AIDS developing
Avoid sexual intercourse/use a condom
Do not share needles
Unless cured by antiretroviral drugs, how does HIV develop?
HIV attacks immune cells
Late stage HIV infection, or AIDS, occurs when the immune system becomes so damaged that it can no longer deal with other infections / cancer
What are the symptoms of TMV?
Mosaic pattern of discolouration on leaves
Restricted growth due to lack of photosynthesis
How is TMV spread?
Direct contact between diseased / healthy plants
How can the spread of TMV be reduced or prevented?
Remove infected plants / their leaves
Wash tools in disinfectant after using them on an infected plant
Explain why TMV causes restricted growth in tomatoes (any plant species)
Parts of the leaves have no chlorophyll
So less light energy is absorbed for photosynthesis
Therefore less glucose made from photosynthesis
And so less proteins made from glucose for growth
Why do Antibiotics not treat HIV, measles or tobacco mosaic virus?
Antibiotics are only effective against bacteria as they do not kill viruses
Suggest reasons for the decrease in the number of new HIV cases in recent years
Better education into the prevention of spread of HIV
Condoms more widely available, easier to source or cheaper
More effective drugs and antiretrovirals to prevent HIV spread
More testing and identification of people with HIV
What is one disadvantage to using antiretroviral drugs to treat HIV?
They do not eliminate HIV completely, so are not considered a cure
What are two bacterial diseases?
Salmonella food poisoning and gonorrhoea
What are the symptoms of salmonella food poisoning?
Fever, abdominal cramps, vomiting and bacteria due to toxins secreted by bacteria
How is salmonella food poisoning spread?
Through bacteria ingested in foods such as chicken, or on food prepared in unhygienic conditions
How can the spread of salmonella food poisoning be reduced or prevented?
In poultry, for example, vaccinate chickens, so fewer bacteria are in chicken and its eggs so fewer bacteria is ingested by humans
Wash hands before preparing food and disinfect surfaces
What are the symptoms of gonorrhoea?
Thick yellow or green discharge from the vagina or penis
Pain during urinating
How is gonorrhoea spread?
Sexually transmitted disease so spread by sexual contact
How can the spread of gonorrhoea be reduced or prevented?
Use of barrier methods of contraception such as condoms
Was easily treated by the antibiotic penicillin until many resistant strains of gonorrhoea appeared
Suggest why the number of cases of salmonella food poisoning is usually higher in summer than in winter
Warmer weather so bacteria reproduce faster
Food not cooked properly on barbecues
Other than vaccination, suggest how farmers could prevent the transmission of salmonella from chickens to humans
Give chickens antibiotics
Do not sell infected chickens and their eggs
Keep infected chickens isolated
Slaughter infected chickens
Name a fungal disease
Rose black spot
What are the symptoms of rose black spot?
Purple or black spots develop which turn yellow and drop early
How is rose black spot spread?
By wind/water
How can the spread of Rose blackspot be prevented or reduced?
Using fungicides or removing affected leaves
What is the effect of rose black spot on plant species?
A reduction in the rate of photosynthesis, causing stunted growth
Name a protist disease
Malaria
What is a symptom of malaria?
Repeating episodes of fever that can be fatal
Describe how mosquitoes are vectors
Mosquitoes pick up the malarial protest when they feed on infected animals
How can the spread of malaria be prevented or reduced?
Preventing vectors (mosquitoes) from breeding, using insecticides, using mosquito nets to avoid being bitten and killing mosquitoes
Describe the non-specific defence systems of the human body that prevent the entry of pathogens
The skin is tough, dry, has a dead outer layer and platelets form scabs over cuts. This acts as a barrier. The skin has antimicrobial secretions that kill pathogens. The skin has sebum that repels pathogens
The nose has hair and mucus that traps pathogens that enter
The trachea and bronchi produce mucus that traps pathogens breathed in and contain cilia that waft mucus up to the throat to be swallowed
The stomach contains hydrochloric acid that kills most pathogens in food or swallowed mucus
The eyes produce antiseptic tears that contain enzymes to kill bacteria
Explain the role of the immune system in the defence against disease
If a pathogen enters the body after passing non-specific defence systems, the immune system tries to destroy the pathogen.
- White blood cells ingest pathogens by phagocytosis. White blood cells can change shape to engulf pathogens and destroy them by secreting enzymes
- B-Lymphocytes produce antibodies which help destroy pathogens by binding to specific antigens on the pathogen.
- White blood cells produce antitoxins to counteract and neutralise the toxins released by pathogens by binding to toxic molecules to prevent them from damaging cells
What are the three ways white blood cells help to defend against pathogens?
Phagocytosis
Antibody production + memory cells
antitoxin production
Define vaccination
Introducing small quantities of dead, inactive (specific) pathogens into the body to stimulate the release of antibodies from white blood cells.
What are the advantages and disadvantages of vaccination?
Vaccines have helped control many communicable diseases and they mean that epidemics can be prevented
However, vaccines are not always effective as they don’t always work and individuals may have bad reactions to it
Explain how immunisation protects us from a named disease
The name disease can be measles, malaria and MMR
A dead or inactive form of the pathogen is injected. The body produces specific antibodies to the antigen on the surface of the pathogen. Memory cells for the antigen on the surface of the pathogen are produced. If the same pathogen enters the body again, memory white cells recognise the pathogens, and produce antibodies rapidly
What are antibiotics?
Antibiotics, such as penicillin, are medicines that help to cure bacterial disease by killing infected bacteria inside the body
It is important that specific bacteria should be treated by specific antibiotics
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The use of antibiotics has greatly reduced deaths from infectious bacterial diseases. However, what is the growing concern?
The emergence of strains resistant to antibiotics
What can antibiotics not kill?
Viral pathogens
What are painkillers used for?
To treat the symptoms of the disease, but do not kill pathogens
Why is it difficult to develop drugs that kill viruses?
Because it may damage the bodies tissues
Explain why antibodies cannot treat viral infections
Viruses are found in the host cell. antibodies cannot get inside the cell. They only target and destroy bacterial cells
Name two antibiotics
Amoxicillin and penicillin
Where does the heart drug digitalis originate from?
Foxgloves
Where does the painkiller aspirin originate from?
Willow
Where does penicillin originate from?
Discovered by Alexander Fleming from the penicillium mould
Most new drugs are synthesised by chemists in the pharmaceutical industry. however, the starting point may still be a chemical extracted from a plant
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Students should be able to describe the process of discovery and development of potential new medicines
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Why do new medical drugs have to be tested and trialled before use?
To check they are safe and effective
What are new drugs tested for?
Toxicity, Efficacy and dose
What is a placebo?
A tablet or injection with no active drug in it
Explain how vaccines work for populations
Through herd or community immunity
If an outbreak occurs, if there is a greater proportion of people immunised against the disease, the less likely it is to spread. A vaccinated population effectively isolates the unvaccinated people from contracting or transmitting disease.
What is a monoclonal antibody?
An antibody made by cloning a white blood cell
Describe how monoclonal antibodies are produced (6)
Inject a mouse with chosen antigen from pathogen
This will stimulate the production of antibodies from B-lymphocytes. This is because the antigen is specific to the antibody
Isolate the lymphocytes that produce the specific antibody from the mouse
Fuse the lymphocytes with tumour cells to form a hybridoma
Clone this
The hybridoma divides rapidly and produces many identical antibodies that are harvested and purified
Explain why monoclonal antibodies are useful
Monoclonal antibodies are produced from single clone of cells
The antibodies are specific to one binding site on one protein antigen
So are able to target a specific antigen chemical or cell in the body
What are some of the uses of monoclonal antibodies?
For diagnosis, such as in pregnancy tests
In laboratories to measure the levels of hormones and other chemicals in blood
To detect pathogens
To treat some diseases such as cancer
In research to locate or identify specific molecules in a cell tissue by binding to them with a fluorescent dye
Describe how monoclonal antibodies can treat diseases
The monoclonal antibody can be bound to a radioactive substance, a toxic drug or a chemical
The mAb will only target diseased/cancerous cells as it is complementary without harming other cells in the body
This stops the Diseased/cancerous cells from growing and dividing as it blocks growth receptors
Describe how monoclonal antibodies are used in pregnancy tests
Why are monoclonal antibodies so powerful?
Powerful research tool as they can be made specific to any antigen
Describe how monoclonal antibodies and a fluorescent dye could be used to detect pathogens on a slide
Bind the fluorescent dye to the monoclonal antibodies
Put the bound dye on the slide and rinse off
mAbs will bind to the antigens on the Candida albicans pathogen and the dye will make it identifiable under the microscope
Explain how increased phagocytosis of the Candida Albicans pathogen will help the patient
The pathogen will be engulfed by pathogens
So there is less damage to cells
How can plant diseases be detected? (7)
Stunted growth
spots on the leaves
areas of decay
growths
malformed stems or leaves
discolouration
Presence of pests
How can plant diseases be identified?
Reference to a gardening manual or website
Taking infected plants to a laboratory to identify the pathogen
Using testing kits that contain monoclonal antibodies (this could be an application question)
What does nitrate deficiency and magnesium deficiency result in?
Nitrate deficiency results in stunted plant growth
Magnesium deficiency results in chlorosis (yellow leaves)
What are the physical defence responses to resist the invasion of microorganisms in a plant?
Cellulose cell walls
Tough waxy cuticle leaves
Layers of dead cells around stems and bark on trees which fall off
What are chemical plant defence responses?
Antibacterial chemicals
Poisons that deter herbivores
What are mechanical adaptations of a plant?
Thorns and hairs that deter animals. Nettles have specialised hairs that act as hypodermic needles, injecting poison
Leaves that droop or curl when touched
Mimicry to trick animals
Explain how clinical trials are carried out
- What is the purpose of placebos and double blind trials?
Suggest two advantages of using a vaccine made of only a small part of the virus, rather than a weakened form of the whole virus
Still contains the antigen for stimulating the release of antibodies
It is safer and there is no risk of contracting disease as viruses CANNOT reproduce
Why do vaccinations contain a small quantity of dead or inactive pathogens instead of live forms?
Explain why diseases can still be prevalent in countries, even if many people are vaccinated against it
Contains the antigen responsible for stimulating the release of antibodies by B-lymphocyte, yet does not cause illness or symptoms
Disease could be spread easily by sneezing or coughing and antibiotics may not be available or too expensive
Explain how MRSA bacteria have evolved to become resistant to antibiotics
(this can be any named bacteria)
Bacteria reproduce rapidly every 20 minutes by binary fission
Mutations of bacterial pathogens can produce new strains
The non-resistant strains are killed and reduce competition
Certain MRSA strains may be resistant to antibiotics and so are not killed
These strains survive and reproduce, so the population of the resistant strain increases
The resistant stain will continue dividing and spread because people are not immune to it and there’s no treatment
