B6.3 Flashcards
What is the relationship between health and disease?
health: state of physical and mental wellbeing
disease: a disorder that affects the body, organs or cells
Describe the 2 different types of diseases, giving examples
communicable diseases are contagious so they can spread between people (e.g. chickenpox, malaria, HIV)
non-communicable diseases are non-contagious (e.g. diabetes, cancer from carcinogens, heart conditions)
Describe the interactions between different types of diseases
HIV and TB:
-HIV affects the strength of the immune system
-TB is a common bacterial disease found in HIV patients as they are more susceptible to infectious diseases
-TB affects the lungs
HPV and Cervical cancer:
-viruses living in cells can trigger cancers
-most cervical cancer cases are linked with the HPV virus
Explain how communicable diseases are spread in plants and animals, and explain how the spread of communicable diseases can be reduced/prevented
Viral infections:
Humans: Human Immunodeficiency Virus (HIV)
-initial flu-like sumptoms
-spread by bodily fluids, commonly through sexual activities or injecting drugs and then sharing needles
-prevented by using condoms, not sharing needles
-complication: can develop into AIDS which remains dominant for some time after HIV and then attacks the immune system
-treatment: drugs exist to stop HIV developing into AIDS but not to prevent HIV
Plants: Tobacco Mosaic Virus
-infects chloroplast levels and changes the green to white spots
-plants cannot photosynthesis correctly and will die
-spread by contact between plants
-prevented by good field hygiene, pest control and growing TMV-resistant strains
Bacterial diseases:
Humans: Salmonella (food poisoning)
-bacteria living in the gut of animals spreading when the meat is ingested by humans
-symptoms: fever, stomach cramps, vomiting, diarrhoea
-spread due to consumption of raw meat and eggs and unhygienic conditions
-prevented by keeping raw meat away from cooked food, wash hands and surfaces when handling it and cook food thoroughly
Plants: crown gall disease (Agrobacterium tumefaciens)
-transfers some of its own DNA to the infect plant’s DNA
-symptoms: like a cancer and a tumour develops in the stems/roots, plants become stunted
Fungal diseases:
Humans: Athlete’s foot
-symptoms: rash found between toes, white/red flaky skin
-spread by touching infected skin or surfaces, so is commonly found in swimming pool changing rooms
-treated with antifungal medication
Plants: barley powdery mildew (Erysiphe graminis)
-affect grass plants, such as barley
-eventually the plant can no longer make chlorophyll and therefore cannot photosynthesise
-symptoms: circular fluffy white growth on leaves, fungus produces spores to reproduce which are spread in the wind, hyphae produced on upper and lower leaf surfaces
-commonly spread in cool, damp areas
-treated with fungicides/removing infected leaves
Protist diseases:
Humans: malaria
-enter red blood cells and replicate, then burst to spread pathogen further
-symptoms: shivering and fevers (caused by the bursting)
-spread by female Anopheles mosquito which is a vector (meaning it is not harmed by the disease but just carries it), protist enters human bloodstream via saliva when mosquito punctures skin to feed on blood
-prevented by using insecticide coated insect nets while sleeping, removing stagnant water to prevent the vectors from breeding, travellers taking antimalarial drugs to kill parasites that enter the blood
The spread of communicable diseases can be reduced by:
-visual identification of disease
-screening for antibodies against virus antigens (such as with HIV)
-DNA identification (e.g. with crown gall disease as it transfers DNA to the plant)
Describe physical plant defence responses to disease
-bark: external layer of dead cells forming barrier against infection
-leaf cuticle: waxy outer layer to prevent pathogens passing through
-cell wall made of cellulose
Describe chemical plant defence responses
Antimicrobial substances:
-mint and witch hazel produce this to prevent the spread of bacteria that were not stripped by physical defences
-used by humans as antiseptics
Poisons:
-stinging nettles release this to stop themselves being eaten
-cyanide is another example
Antibacterial compounds to kill bacteria
-e.g. phenols, disrupt the bacterial cell wall, which disrupts the cell membrane
Explain how white blood cells and platelets are adapted to their defence functions in the blood
White blood cells:
-work by phagocytosis (pathogen is engulfed and then killed)
-produce antitoxins that WBCs neutralise by binding to the toxins of the pathogen
-produce antibodies (lymphocytes)
-each pathogen has an antigen on their surface which is a structure which a specific complementary antibody can bind to
-once antibodies begin to bind to the pathogen, the specific complementary antibodies will be produced at a fast rate
-the person will not feel symptoms, so they are now immune
Platelets:
-have proteins on their surface that helps them to clump together to heal a wound
-secrete proteins that result in a clotting cascade (a chain reaction of different chemical reactions to help with forming clots)
Describe the non-specific defence systems in humans against pathogens
Skin:
-acts as a physical barrier
-produces antimicrobial secretions to kill pathogens
-good microorganisms known as skin flora compete with the bad microorganisms for space and nutrients
Nose:
-has hairs and mucus which prevent particles from entering your lungs
Trachea and bronchi:
-secrete mucus to trap pathogens
-cilia (hair-like structures on cells) beat to waft mucus upwards so it can be swallowed
Stomach:
-produces hydrochloric acid that kills pathogens in your mucus, or food and drink
Phagocytic white blood cells:
-one type of white blood cell can do a process called phagocytosis, where the pathogen is engulfed and killed
-as they are able to do this with any type of pathogen, it is a non-specific function
Explain the role of the immune system of the human body in defence against disease
What are monoclonal antibodies and describe how they are produced
Monoclonal antibodies are identical antibodies, that have been produced from the same lymphocyte (a type of white blood cell). As a result of their ability to bind to only one protein antigen, they can be used to target chemicals and cells in the body and so have many different medical uses, e.g. in pregnancy testing.
How they are produced
1) An antigen is injected into a mouse
2) The mouse produces lymphocytes, which have been stimulated to produce a specific
antibody to the injected antigen.
3) Spleen cells from the mouse are removed, as this is where the lymphocytes are
produced
4) The spleen cells are combines with human cancerous white blood cells called myeloma
cells to form a cell called a hybridoma, which divides indefinitely
5) The hybridoma can divide to produce clones of itself, which all produce the same
antibody many times.
6) The antibodies are collected and purified
Describe some ways in which monoclonal antibodies can be used
Pregnancy tests:
-a hormone called human chorionic gonadotrophin (hCG) is present in the urine of women who are pregnant
-there are two sections of the stick.
-first section has mobile antibodies complementary to the hCG hormone- these
antibodies are also attached to blue beads.
-second section has stationary antibodies complementary to the hCG hormone
which are stuck down to the stick.
-a person urinates on the first section, and if hCG is present it binds to the mobile
antibodies attached to blue beads to form hCG/antibody complexes.
-they are carried in the flow of liquid to the second section.
-the stationary antibodies then bind to the HCG/antibody complexes.
-they are each bound to a blue bead, this results in a blue line, indicating that you are pregnant
Diagnosis of cancer:
-cancerous cells have antigens
-monoclonal antibodies can be designed to bind to these specific antigens, causing them to clump together
-they may have a marker, such as a fluorescent dye, attached to them to help identify the location of the tumour in the body
-once the tumour is identified, it can be treated or removed
-monoclonal antibodies have successfully been used to detect and treat prostrate cancer in men
Treatment of cancer:
-drugs can be attached to the monoclonal antibody so that when it binds to the cancer antigen it can deliver the toxic substance
-better than radiotherapy and chemo as it will only target cancer cells, reducing side effects
-can also encourage white blood cells in the immune system to attack the cancer cells directly
Describe different ways plant diseases can be detected and identified, in the lab and in the field
ELISA (Enzyme-Linked Immunosorbent Assay)
This can be used to see whether a plant contains a pathogen antigen and is therefore infected
1) Liquidise plant sample
2) Add sample to plastic tube or microtiter plate
3) Leave for 5 minutes so that all the proteins in the plant have bound to the plastic
4) Wash the wells with buffered salt solution to wash off any excess protein that has not
bound to the plastic
5) Add blocking agent to block any uncoated plastic and then wash off again with the salt
solution
6) Add an antibody-enzyme complex specific to the pathogen antigen and then wash off
with the salt solution
7) Add a colourless substrate that the enzyme will change to a coloured product so if the
pathogen antigen is in the liquid the tube will change colour.
Polymerase chain reaction (PCR)
A process allowing a small section of DNA to be copied billions of times
1) Add 2 primers, nucleotides and DNA polymerase into tube
● 2 primers (short pieces of DNA) are needed to match each end of the DNA
segment that is meant to be copied
● DNA polymerase reads the DNA and makes a copy, by attaching nucleotides at at
a primer
2) The DNA is heated to 95°C to unzip the double helix of DNA and denature it
3) It is cooled to 55°C to allow the primers to anneal
4) It is heated to 72°C as this is the optimum time for DNA polymerase to work
Observation
Observation is not only how the plant looks, but also the feel and smell etc. For example: stunted growth, presence of fungus. We can also use microscopy to detect diseased leaves
What are specific defences and what are the two types
The specific immune system destroys any pathogens which pass through the non-specific immune system in the body
2 examples include white blood cells and platelets
Describe the advantages and disadvantages of using monoclonal antibodies
Advantages:
-only bind to specific cells , meaning healthy cells are not affected
-can be engineered to treat many different conditions
-we’re now able to produce mouse-human hybrid cells to reduce the chance of triggering an immune response
Disadvantages:
-difficult to attach monoclonal antibodies to drugs
-expensive to develop
-as they were produced from mice lymphocytes, they often trigged an immune response when used in humans
Explain the use of vaccines and medicines in the prevention and treatment of disease
Vaccines:
-make an individual immune to a certain disease, so they are protected before they have been infected
-if a large amount of the population is immune, the spread of the pathogen is reduced, as less people will catch it (called herd immunity)
-contains a dead or inactivated form of the pathogen, which stimulates white blood cells to produce antibodies complementary to the antigens on the pathogen
Antibiotics:
-medicines that kill bacterial pathogens inside the body, without damaging body cells
-cannot kill viruses as they use body cells to reproduce, meaning any drugs that target them would affect body tissue too
-can be taken as a pill, syrup or directly into bloodstream
-has decreased the number of deaths from bacterial diseases, such as with pencillin
Antivirals:
-used to stop virus replication
-virus hijacks cell’s normal processes in order to copy its own DNA, so it would not be possible to kill the virus without damaging human cells, so stopping replication is the only way
Antiseptics:
-chemicals that kill foreign microorganisms
-commonly used in sterilising a wound to avoid infection and therefore the spread of disease
