Topic 3- Infection and Response. Flashcards
1
Q
what are pathogens?
A
Pathogens are MICROORGANISMS that enter the body and cause DISEASE.
2
Q
What type of disease do pathogens cause?
A
They cause COMMUNICABLE (infectious) diseases-diseases that can SPREAD.
3
Q
What do pathogens infect?
A
Both plants and animals can be infected by pathogens.
4
Q
How many types of pathogen are there?
A
There are several types of pathogen.
5
Q
What are bacteria?
A
Bacteria are VERY SMALL CELLS (about 1/100th the size of your body cells), which can reproduce rapidly inside your body.
6
Q
How do bacteria cause illness?
A
They can make you FEEL ILL by PRODUCING TOXINS (poisons) that DAMAGE YOU CELLS and TISSUES.
7
Q
What are viruses?
A
Viruses are NOT CELLS. They’re TINY, about 1/100th the size of bacterium.
Like bacteria, they can reproduce rapidly inside your body.
8
Q
How do viruses cause illness?
A
They live inside your cells and REPLICATE THEMSELVES using the cells’ MACHINERY to produce many COPIES of themselves. The cell will usually then BURST, releasing all the new viruses.
This CELL DAMAGE is what makes you feel ill.
9
Q
What are the characteristics of protists?
A
There are lots of different types of protists. But they’re all EUKARYOTES and most of them are SINGLE-CELLED.
Some protists are PARASITES.
10
Q
What are parasites?
A
Parasites live ON or INSIDE other organisms and can cause them DAMAGE. They are often transferred to the organism by a VECTOR, which doesn’t get the disease itself- e.g. an insect that carries the protist.
11
Q
What are the characteristics of fungi?
A
-Some fungi are SINGLE-CELLED. Others have a BODY which is made up of HYPHAE (thread like structures)
These hyphae can GROW and PENETRATE HUMAN SKIN and the SURFACE OF PLANTS, causing DISEASES.
The hyphae can produce SPORES, which can be spread to other plants and animals.
12
Q
How can pathogens spread?
A
Pathogens can spread through:
- Water
- Air
- Direct contact
13
Q
How can pathogens be spread by water?
A
Some pathogens can be picked up by drinking or bathing in DIRTY WATER.
E.g. CHOLERA is a BACTERIAL INFECTION that’s spread by DRINKING water CONTAMINATED with the diarrhoea of other sufferers.
14
Q
How can pathogens be spread by air?
A
Pathogens can be carried in the AIR and can be BREATHED IN.
Some airborne pathogens are carried in the air in DROPLETS produced when you COUGH or SNEEZE-e.g. the INFLUENZA VIRUS that causes FLU is spread this way.
15
Q
How can pathogens be spread by direct contact?
A
Some pathogens can be picked up by TOUCHING contaminated surfaces, including the SKIN.
E.g. ATHLETE’S FOOT is a FUNGUS which makes skin itch and flake off. It’s most commonly spread by touching the same things as an infected person, e.g. SHOWER FLOORS and TOWELS.
16
Q
What is measles?
A
Measles is a VIRAL disease.
17
Q
How is measles virus spread?
A
It is spread by DROPLETS from an infected person’s sneeze or cough.
18
Q
What are the symptoms of measles?
A
People with measles develop a RED SKIN RASH, and they’ll show signs of a FEVER (a high temperature).
19
Q
Is measles a very serious condition?
A
Measles can be a very serious, or even fatal, if there are COMPLICATIONS. For example, measles can sometimes lead to PNEUMONIA (a lung infection) or a brain infection called ENCEPHALITIS.
20
Q
How is measles prevented?
A
Most people are VACCINATED against measles when they’re young.
21
Q
What is HIV?
A
HIV is a VIRUS.
22
Q
Outline how HIV virus can be spread.
A
It can spread by SEXUAL CONTACT, or by changing BODILY FLUIDS such as blood. This can happen when people SHARE NEEDLES when taking drugs.
23
Q
What are the symptoms of HIV?
A
HIV initially causes FLU-LIKE SYMPTOMS for a few weeks. Usually, the person doesn’t than experience any symptoms for several years.
24
Q
During the early stages of HIV (in the 7 year period where there are no symptoms) what type of drugs are used?
A
During this time, HIV can be controlled with ANTIRETROVIRAL DRUGS. These stop the virus REPLICATING in the body.
25
How does the virus HIV attack the body?
The virus attacks the IMMUNE CELLS.
26
How does the HIV disease progress to late stage HIV infection or AIDS?
If the body's immune system is badly damaged, it CAN'T COPE with OTHER INFECTIONS or CANCERS. At this stage, the virus is known as LATE STAGE HIV INFECTION, or AIDS.
27
What is tobacco mosaic virus (TMV)?
TMV is a VIRUS that affects many species of PLANTS.
28
Name one type of plant that can be infected by the tobacco mosaic virus.
Tomatoes.
29
What are the symptoms of tobacco mosaic virus?
It causes a mosaic pattern on the leaves of the plants- parts of the leaves become DISCOLOURED.
30
Explain why growth is affected in a plant infected with tobacco mosaic virus.
The discolouration means the plant can't carry out PHOTOSYNTHESIS as well, so the virus affects growth.
31
Give an example of a fungal disease in a plant.
ROSE BLACK SPOT is a FUNGUS.
32
What are the symptoms of rose black spot?
It causes PURPLE OR BLACK SPOTS to develop on the LEAVES of ROSE PLANTS. The leaves can then turn YELLOW and DROP OFF.
33
Explain why being infected with rose black spot affects the growth of a plant.
Due to the purple/black spots- this means that less PHOTOSYNTHESIS can happen, so the plant doesn't GROW very well.
34
How is rose black spot spread?
It spreads through the environment in WATER or by WIND.
35
How can rose black spot be treated?
Gardeners can treat the disease using FUNGICIDES and by STRIPPING the plant of its AFFECTED LEAVES. These leaves then need to be DESTROYED so that the fungus can't spread to other rose plants.
36
What is malaria caused by?
Malaria is caused by a PROTIST.
37
Where does part of the life cycle of the malaria protist take place?
Part of the malaria protists LIFE CYCLE takes place inside the mosquito. The mosquitoes are VECTORS- they PICK UP the malarial protist when they FEED on an INFECTED ANIMAL.
38
How can someone become infected by malaria?
Every time the mosquito feeds on another animal, it INFECTS IT by inserting the protist into the animal's blood vessel.
39
What are the symptoms of malaria?
Malaria causes REPEATING episodes of FEVER. It can be FATAL.
40
How can the spread of malaria be reduced?
The SPREAD of malaria can be reduced by stopping the MOSQUITOES from BREEDING.
41
Why are mosquito nets used in areas with high risk of malaria?
People van be protected from mosquitoes using INSECTICIDES and MOSQUITO NETS.
42
What is salmonella?
Salmonella is a type of BACTERIA that causes FOOD POISONING.
43
What are the 4 symptoms of salmonella?
Infected people can suffer from FEVER, STOMACH CRAMPS, VOMITING and DIARRHOEA.
44
How can someone get salmonella?
You can get salmonella food poisoning by eating FOOD that's been CONTAMINATED with salmonella bacteria, e.g. eating chicken that caught the disease whilst it was alive, or eating food that has been contaminated by being prepared in unhygienic conditions.
45
How is the spread of salmonella reduced?
In the UK, most POULTRY (e.g. chickens and turkeys) is given a VACCINATION against Salmonella. This is to control the SPREAD of the disease.
46
What is gonorrhoea?
What is it caused by?
Gonorrhoea is a SEXUALLY TRANSMITTED DISEASE (STD) caused by BACTERIA.
47
How are STDs spread?
STDs are passed on by SEXUAL CONTACT, e.g. having unprotected sex.
48
What are the symptoms of gonorrhoea?
A person with gonorrhoea will get PAIN when they URINATE. Another symptom is a thick yellow or green DISCHARGE from the VAGINA or the PENIS.
49
Why is gonorrhoea not easily treated with penicillin anymore?
Gonorrhoea was originally treated with an ANTIBIOTIC called PENICILLIN, but this has become trickier now because strains of the bacteria have become RESISTANT to it.
50
How is the spread of gonorrhoea controlled?
To prevent the SPREAD of gonorrhoea, people can be treated with antibiotics and should use BARRIER METHODS of contraception, such as CONDOMS.
51
How can the spread of disease be reduced or prevented by being hygienic?
Using simple hygiene measures can prevent the spread of disease.
For example, doing things like WASHING YOUR HANDS thoroughly before preparing food or after you've sneezed can stop you infecting another person.
52
How can the spread of disease be reduced or prevented by destroying vectors?
By getting rid of the organisms that spread disease, you can prevent the disease from being passed on. Vectors that are INSECTS can be killed using INSECTICIDES or by DESTROYING their HABITAT so that they can no longer bread.
53
How can the spread of disease be reduced or prevented by isolating infected individuals?
If you isolate someone who has a communicable disease, it PREVENTS them from PASSING IT ON to anyone else.
54
How can the spread of disease be reduced or prevented by vaccination?
Vaccinating people and animals against communicable diseases means that they CAN'T develop the infection and then PASS IT ON to someone else.
55
What are the body's non-specific defence systems which prevent pathogens from entering?
1. Skin
2. Hairs
3. Trachea and Bronchi
4. Cilia
5. Stomach-HCL
56
How does the skin prevent pathogens from entering?
The SKIN acts as a BARRIER to pathogens. It also secretes ANTIMICROBIAL SUBSTANCES which kill pathogens.
57
How do hairs prevent pathogens from entering?
HAIRS and MUCUS in your nose TRAP particles that could contain pathogens.
58
How does the trachea and bronchi defend against pathogens?
The TRACHEA and BRONCHI (breathing pipework) secrete MUCUS to trap pathogens.
59
How does cilia defend against pathogens?
The trachea and bronchi are lined with CILIA. These are hair-like structures, which WAFT THE MUCUS up to the back of the throat where it can be SWALLOWED.
60
How does the stomach defend against pathogens?
The STOMACH produces HYDROCHLORIC ACID. This kills pathogens that make it that far from the mouth.
61
Explain the role of the immune system.
If pathogens do make it into your body, your IMMUNE SYSTEM kicks in to destroy them.
62
Give three ways in which white blood cells help to defend the body against disease.
1. CONSUMING THEM
2. PRODUCING ANTITOXINS
3. PRODUCING ANTIBODIES
63
How do white blood cells consume pathogens?
1. CONSUMING THEM
| White blood cells can ENGULF foreign cells and digest them. This is called PHAGOCYTOSIS.
64
How do white blood cells produce antitoxins?
2.PRODUCING ANTITOXINS
| These counteract toxins produced by the INVADING BACTERIA.
65
How do white blood cells produce antibodies?
3. PRODUCING ANTIBODIES
1) Every invading pathogen has unique molecules (called ANTIGENS) on its surface.
2) When some types of white blood cell come across a FOREIGN ANTIGEN (i.e. one they don't recognise), they will start to produce PROTEINS called ANTIBODIES to lock onto the invading cells so that they can be DOUND and DESTROYED by other white blood cells. The antibodies produced are specific to that type of antigen- they won't lock on to any others.
3) Antibodies are then produced RAPIDLY and carried around the body to find all similar bacteria or viruses.
4) If the person is infected with the same pathogen again the white blood cells will rapidly produce the antibodies to kill it- the person is NATURALLY immune to that pathogen and won't get ill.
66
What are the white blood cells that produce antibodies called?
The white blood cells that produce antibodies are also known as B-lymphocytes.
67
Exam tip: Don't get antigens and antibodies mixed up in the exam. Remember, the BODY makes antiBODIES against the antiGENS on pathoGENS.
What is the purpose of vaccinations?
When you're infected with a new PATHOGEN, it takes your white blood cells a few days to LEARN how to deal with it. But by that time, you can be pretty ILL.
But vaccinations allow your body to rapidly lear how to cope,so that you don't become ill in the first place.
68
How do vaccinations work?
Give an example.
Vaccinations involve injecting small amounts of DEAD or INACTIVE pathogens. These carry ANTIGENS, which cause your body to produce ANTIBODIES to attack them-even though the pathogen is HARMLESS (since it's dead or inactive).
For example, the MMR vaccine contains WEAKENED versions of the viruses that cause MEASLES, MUMPS and RUBELLA (german measles) all in one vaccine.
But if live pathogens of the same type appear after that, the white blood cells can RAPIDLY mass-produce antibodies to kill off the pathogen.
69
Can weakened viruses in the MMR vaccine cause disease?
The weakened viruses in the MMR vaccine are still alive, but aren't able to cause disease.
70
Why are booster injections given?
Some vaccinations wear off over time. So booster injections may need to be given to increase the levels of antibodies again.
71
What are the pros of vaccinations?
1) Vaccines have helped to CONTROL lots of communicable diseases that were once COMMON in the UK (e.g. polio, measles, whooping cough, rubella, mumps, tetanus..).
2) Big outbreaks of disease- called EPIDEMICS- can be prevented if a LARGE PERCENTAGE of the population is vaccinated. That way, even the people who aren't vaccinated are UNLIKELY to catch the disease because there are FEWER people able to PASS IT ON. But if a significant number of people AREN'T vaccinated, the disease can SPREAD quickly through them and lots of people will be ILL at the same time.
72
What are the cons of vaccinations?
1) Vaccinations don't always work- sometimes they DON'T give you IMMUNITY.
2) You can sometimes have a BAD REACTION to a vaccine (e.g. swelling, or maybe something more serious like a fever or seizures). But bad reactions are very RARE.
73
True or false?
Painkillers can be used to tackle the cause of an infection.
What is the purpose of painkillers?
FALSE.
Painkillers (e.g. aspiring) are drugs that relieve pain. However, they don't actually tackle the CAUSE of the disease or KILL pathogens, they just help to reduce the SYMPTOMS.
74
What do cold remedies do?
Similar to painkillers, cold remedies reduce the SYMPTOMS without tackling the underlying CAUSE.
75
What are antibiotics?
ANTIBIOTICS (e.g. penicillin) work differently-they actually KILL (or prevent the growth of ) the bacteria causing the problem without killing your own body cells. Different antibiotics kill different types of bacteria, so it's important to be treated with the right one.
76
Explain why it can be difficult to develop drugs that kill viruses.
Antibiotics DO NOT destroy VIRUSES (e.g. cold or flu viruses). Viruses reproduce USING YOUR BODY CELLS, which makes it very difficult to develop drugs that destroy just the virus without killing the body's cells.
77
What is an advantage of the use of antibiotics?
The use of antibiotics has GREATLY REDUCED the number of deaths from communicable diseases caused by bacteria.
78
Why is it important to be treated with the right antibiotic for a particular infection?
Because different antibiotics kill different types of bacteria.
79
How can antibiotic strains of bacteria develop?
Bacteria can MUTATE- sometimes the mutations cause them to be RESISTANT to (not killed by) an ANTIBIOTIC.
If you have an INFECTION, some of the bacteria might be RESISTANT to antibiotics.
This means that when you TREAT the infection, only the NON-RESISTANT strains of bacteria will be KILLED.
The individual RESISTANT bacteria will SURVIVE and REPRODUCE, and the population of the resistant strain will INCREASE. This is an example of NATURAL SELECTION.
This resistant strain could cause a SERIOUS INFECTION that CAN'T be treated by antibiotics.
80
Why is it important not to over-use antibiotics?
To SLOW DOWN the RATE of RESISTANT STRAINS, it's important for doctors to AVOID OVER-PRESCRIBING antibiotics. So you WON'T get them for a SORE THROAT, only for something more serious.
81
How can we stop the development of antibiotic strains of bacteria?
We can do this by making sure that when using antibiotics you FINISH your WHOLE COURSE of antibiotics and don't just stop when you feel better.
82
What were drugs in the past extracted from and why?
PLANTS produce a variety of CHEMICALS to DEFEND against PESTS and PATHOGENS.
Some of these chemicals can be used as DRUGS to treat human diseases or RELIEVE SYMPTOMS.
A lot of our CURRENT MEDICINES were discovered by studying plants used in TRADITIONAL CURES.
83
Traditionally drugs were extracted from plants.
Give an example of a current medicine that was discovered by studying plants used in traditional cures.
ASPIRIN is used as a PAINKILLER and to lower FEVER. It was developed from a chemical found in WILLOW.
84
Which drug originates from the plant willow?
Aspirin.
85
Which drug was developed from a chemical found in foxgloves?
DIGITALIS was developed from a chemical found in FOXGLOVES.
86
What id digitalis used to treat?
DIGITALIS is used to treat HEART CONDITIONS.
87
Who discovered penicillin and how was it discovered?
Penicillin was discovered by Alexander Fleming.
Alexander Fleming was clearing out some Petri dishes containing BACTERIA. He noticed that one of the dishes of bacteria also had MOULD on it and the AREA AROUND THE MOULD was FREE of the BACTERIA.
He found that the MOULD on the Petri dish was producing a substance that KILLED THE BACTERIA- this substance was PENICILLIN.
88
What drug originates from a microorganism?
Penicillin.
89
How are drugs produced now?
These days, drugs are made on a large scale in the PHARMACEUTICAL INDUSTRY- they're synthesised by chemists in labs. However, the process still might start with a chemical EXTRACTED from a PLANT.
90
Why do new medicinal drugs have to be tested before becoming available to the public?
Before new drugs can be given to the general public, they have to go through a thorough TESTING procedure to make sure they are SAFE and EFFECTIVE.
91
What are the three main stages in drug testing?
The three main stages are:
1) PRECLINICAL TESTING ON HUMAN CELLS AND TISSUES.
2) PRECLINICAL TESTING ON LIVE ANIMALS.
3) PRECLINICAL TESTING ON HUMAN VOLUNTEERS.
92
What does the first stage of, preclinical testing on human cells and tissues entail?
1) In preclinical testing, drugs are tested on HUMAN CELLS and TISSUES in the lab.
2) However, you can't use human cells and tissues to test drugs that affect WHOLE or MULTIPLE body systems, e.g. testing a drug for blood pressure must be done on a whole animal because it has an intact circulatory system.
93
What does the second stage of , preclinical testing on live animals entail?
1) The next step in preclinical testing is to test the drug on LIVE ANIMALS. This is to test EFFICACY (whether the drug WORKS and produces the effect you're looking for), to find out about its TOXICITY (how harmful it is) and to find the best DOSAGE (the concentration that should be given, and how often it should be given).
2) The law in Britain states that any new drug must be tested on TWO different LIVE MAMMALS. Some people think it's CRUEL to test on animals, but others believe this is the AFEST way to make sure a drug isn't sangria before it's given to humans.
94
What does the third stage preclinical testing on human volunteers entail?
1) If the drug PASSES the tests on animals then it's tested on HUMAN VOLUNTEERS in a CLINICAL TRIAL.
2) First, the drug is tested on HEALTHY volunteers. This is to make sure that it doesn't have any HARMFUL SIDE EFFECTS when the body is working normally. At the start of the trial, a VERY LOW DOSE of the drug is given and this is gradually increased.
3) If the results of the tests on healthy volunteers are good, the drugs can be tested on people suffering from the ILNESS. The OPTIMUM DOSE is found- this is the dose of the drug that is the MOST EFFECTIVE and has FEW SIDE EFFECTS.
95
What is a placebo?
A PLACEBO is a substance hat's like the drug being tested but doesn't do anything.
A placebo is usually a tablet or an injection with no drug added.
96
Why are placebo's used?
To test how well the drugs work, patients are RANDOMLY put into TWO GROUPS. One is given the NEW DRUG, the other is given a PLACEBO (a substance that's like the drug being tested but doesn't do anything).
This is so the DOCTOR can see the actual difference the drug makes- it allows for the PLACEBO EFFECT.
97
Briefly explain what is involved in a double-blind trial.
Clinical trials are BLIND-the patient in the study DOESN'T KNOW whether they're getting the drug or the placebo. In fact, they're often DOUBLE-BLIND-neither the patient nor the DOCTOR knows until all the RESULTS have been gathered. This is so the doctors MONITORING the patient and ANALYSING the result aren't SUBCONSCIOUSLY INFLUENCED by their knowledge.
98
When are the results of drug testing published?
The results of drug testing and drug trials aren't published until they've been through PEER REVIEW.
This helps to prevent FALSE CLAIMS.
99
What are monoclonal antibodies?
Monoclonal antibodies are antibodies produced from lots of clones a single white blood cell, which will only target one specific protein antigen.
100
*Describe how monoclonal antibodies are produced?
Antibodies are produced by B-lymphocytes- a type of white blood cell.
MONOCLONAL ANTIBODIES are produced from LOTS OF CLONES of a single white blood cell. This means all the antibodies are IDENTICAL and will only target ONE specific PROTEIN ANTIGEN.
However, you can't just grab the lymphocyte that made the antibody and grow more-lymphocytes DON'T DIVIDE VERY EASILY.
TUMOUR CELLS, on the other hand don't produce antibodies but DIVIDE LOTS- so they can be GROWN REALLY EASILY.
It's possible to FUSE a mouse B-lymphocyte with a TUMOUR CELL to create a cell called a HYBRIDOMA.
Hybridoma cells can be CLONED to get LOTS of identical cells. These cells all produce the same ANTIBODIES (MONOCLONAL ANTIBODIES). The antibodies can be COLLECTED and PURIFIED.
You can make monoclonal antibodies that BIND TO ANYTHING you want, e.g. an antigen that's only found on the surface of one type of cell. Monoclonal antibodies are really useful because they will ONLY bind to (target) THIS MOLECULE- this means you can use them to target a specific cell or chemical in the BODY.
101
What two things are fused to make a hybridoma cell?
A mouse B-lymphocyte and a tumour cell.
102
What happens in monoclonal antibody production after a hybridoma cell has been made?
The hybridoma cells are cloned to get lots of identical cells that all produce the same antibodies (monoclonal antibodies). These are collected and purified.
103
How are monoclonal antibodies used in pregnancy tests?
A HORMONE called HCG is found in the URINE of women ONLY when they are PREGNANT. Pregnancy testing sticks detect this hormone.
104
Describe how monoclonal antibodies can be used for diagnosis, e.g. in pregnancy tests?
THE TEST STICK
1) The bit of the stick you WEE ON has some ANTIBODIES to the hormone, with BLUE HEADS ATTACHED.
2) The TEST STRIP (the bit of the stick that turns blue if you're pregnant) has some more antibodies to the hormone STUCK ON IT (so they can't move).
IF YOU'RE PREGNANT
3) If you're PREGNANT and you wee on the stick:
- The HORMONE BINDS to the ANTIBODIES on the BLUE BEADS.
- The urine MOVES UP the stick, CARRYING the hormone and the beads.
- The beads and hormone BIND to the ANTIBODIES on the strip.
- So the BLUE HEADS get STUCK ON THE STRIP, turning it BLUE.
IF YOU'RE NOT PREGNANT
4) If you're NOT PREGNANT and you wee on the stick, the urine STILL moves up the stick, carrying the BLUE BEADS. But there's NOTHING to STICK the blue beads onto the TEST STRIP, so it DOESN'T GO BLUE.
105
Describe how monoclonal antibodies can be used to treat diseases?
1) DIFFERENT CELLS in the body have DIFFERENT ANTIGENS on their cell SURFACE. So you can make monoclonal antibodies that will bind to SPECIFIC CELLS in the body (e.g. just liver cells).
2) Cancer cells have ANTIGENS on their CELL MEMBRANES that AREN'T found on normal body cells. They're called TUMOUR MARKERS.
3) In the lab, you van make MONOCLONAL ANTIBODIES that will bind to these tumour markers.
4) An ANTI-CANCER DRUG can be attached to those monoclonal antibodies. This might be a RADIOACTIVE substance, a TOXIC DRUG or a chemical which stops cancer cells GROWING and DIVIDING.
5) The antibodies are GIVEN to the patient through a drip.
6) The antibodies TARGET SPECIFIC CELLS (the cancer cells) because they only bind to the TUMOUR MARKERS.
7) The drug KILLS the CANCER CELLS but DOESN'T kill any ABNORMAL BODY CELLS near the tumour.
106
Describe how monoclonal antibodies can be used in laboratories.
Monoclonal antibodies can be used in laboratories to:
- Bind to HORMONES and other CHEMICALS in BLOOD to measure their levels.
- Test blood samples for certain PATHOGENS.
107
Describe how monoclonal antibodies can be used in research.
Monoclonal antibodies can be used in research to:
- LOCATE specific molecules on a CELL or in a TISSUE:
1) First monoclonal antibodies are made that will bind to the specific molecules you're looking for.
2) The antibodies are then bound to a FLUORESCENT DYE.
3) If the molecules are present in the sample you're analysing, the monoclonal antibodies will ATTACH to them, and they can be DETECTED using a dye.
108
What are the problems with the use of monoclonal antibodies?
Monoclonal antibodies cause MORE SIDE EFFECTS than were ORIGINALLY EXPECTED, e.g. they can cause fever, vomiting and low blood pressure. When they were first developed, scientists thought that because they targeted a very specific cell or molecule, they wouldn't create a lot of side effects.
This means that they are NOT AS WIDELY USED as treatments as scientists had originally thought they might be.
109
What pathogens cause plant diseases?
Plants can be infected by a range of viral, bacterial and fungal pathogens as well as by insects.
110
What happens to plants that are lacking in mineral ions?
Plants need MINERAL IONS from the SOIL. If there aren't enough, plants suffer DEFICIENCY SYMPTOMS.
111
Why are nitrate ions needed in a plant?
What occurs if there's a lack of nitrates?
Nitrates are needed to make PROTEINS and therefore for GROWTH.
A lack of nitrates causes STUNTED GROWTH.
112
Why are magnesium ions needed in a plant?
MAGNESIUM IONS are needed for making CHLOROPHYLL, which is needed for PHOTOSYNTHESIS. Plants without enough magnesium suffer from CHLOROSIS and have YELLOW LEAVES.
113
How are plant diseases detected?
It's usually pretty clear that a plant has a disease. The common signs are:
1) Stunted growth 2)Abnormal GROWTHS, e.g. lumps
3) SPOTS on the leaves 4) Patches of DECAY
5) MALFORMED stems or leaves
6) DISSCOLOURATION.
7) They can also be INFESTED and damaged by INSECTS. For example, APHIDS are an INSECT that can cause huge DAMAGE to plants.
114
How can plant disease be identified?
1) Looking up the signs in a GARDENING MANUAL or on a GARDENING WEBSITE.
2) Taking the infected plant to a LABORATORY, where scientists can identify the pathogen.
3) Using TESTING KITS that identify the pathogen using MONOCLONAL ANTIBODIES.
115
How do plants defend themselves against pathogens?
Plants have PHYSICAL, CHEMICAL and MECHANICAL defences against pests and pathogens.
116
What are the 3 physical defences plants have against pathogens?
1) Most plant leaves and stems have a WAXY CUTICLE, which provides a BARRIER to stop pathogens entering.
2) Plant cells themselves are surrounded by CELL WALLS made from CELLULOSE.
These form PHYSICAL BARRIERS against pathogens that make it through the waxy cuticle.
3) Plants have LAYERS of DEAD CELLS around their STEMS, for example, the outer part of the BARK on trees. These act as a BARRIER to stop pathogens entering.
117
What are the 2 chemical defences plants have against pathogens or pests?
1) Some can produce ANTIBACTERIAL CHEMICALS which kill bacteria- e.g. the MNT PLANT and WITCH HAZEL.
2) Other plants produce POISONS which can deter herbivores e.g. TOBACCO PLANTS, FOXGLOVES and DEADLY NIGHTSHADE.
118
What are the 3 mechanical defences plants have against pathogens or pests?
1) Some plants have adapted to have THORNS and HAIRS. These STOP animals from TOUCHING and EATING them.
2) Other plants have leaves that DROOP or CURL when something touches them. This means that they can prevent themselves from being eaten by knocking INSECTS off themselves and MOVING AWAY from things.
3) Some plants can cleverly MIMIC other organisms. E.g. the PASSION FLOWER has BRIGHT YELLOW SPOTS on its leaves which look like BUTTERFLY EGGS. This stops other butterflies laying their eggs there. Several species of plant in the 'ice plant family' in southern Africa look like STONES and PEBBLES. This TRICKS other organisms into not eating them.
