GCSE biology - topic 3 (B5 + B6)

what are pathogens?

disease causing microorganisms

what type of disease do pathogens cause?

communicable

what microorganisms do pathogens affect?

both plants and animals

what are bacteria?

very small cells which can reproduce rapidly inside your body

what do bacteria do?

make you ill by producing toxins that damage your cells and tissues

how big are bacteria?

1/100th the size of your body cells

what are viruses NOT?

cells

how big are viruses?

1/100th the size of a bacterium

what do viruses do similarly to bacteria?

reproduce rapidly inside your body

where do viruses live?

inside your cells and they replicate themselves using the cells machinery to produce many copies of themselves

what will happen after viruses replicate in your cells?

the cells will usually then burst, releasing all the new viruses. This cell damage is what makes you feel ill

what are all protists?

eukaryotes and most of them are single celled

what are some protists?

parasites

where do parasites live?

on or inside other organisms and can cause them damage

how are parasites transferred?

by a vector, which doesnt get the disease itself

what are some fungi?

single celled

what do other fungi have?

a body which is made up of hyphae

what are hyphae and what does it do?

thread like structures which can grow and penetrate human skin and the surface of plants, causing diseases

what can hyphae produce?

spores, which can be spread to other plants and animals

what are the 3 ways pathogens can be spread?

water, air, and direct contact

how can pathogens be spread by water?

via drinking or bathing in dirty water, eg. Cholera, a bacterial infection spread via drinking water contaminated with the diarrhoea of others.

how can pathogens be spread by air?

they are carried in the air and breathed in, or via airborne droplets from coughing and sneezing, eg. the influenza virus

how can pathogens be spread by direct contact?

from touching contaminated surfaces, like the skin, eg. athletes foot, a fungus spread by touching the same things as an infected person (towels etc)

what are some viral disease examples?

measles, HIV, and tobacco mosaic virus (TMV)

what is measles spread by?

airborne droplets

what are symptoms of measles?

red skin rash, and a fever

what are complications of measles?

can be fatal, and it can sometimes lead to pneumonia or a brain infection called encephalitis

how do you prevent measles?

getting vaccinated when young

what is HIV spread by?

sexual contact, exchanging bodily fluids (breast milk and blood), and sharing needles

what are HIV symptoms?

initially causes flu like symptoms

how can HIV be controlled while you have it?

antiretroviral drugs, which stops the virus replicating in the body

what does the virus HIV attack in the body?

the immune cells

does HIV have a treatment?

no

what happens if the immune system gets badly damaged from HIV?

the immune system wont cope with other infections or cancers. This is last stage HIV / AIDS

how do you prevent HIV?

bottle feeding, not sharing needles, using the barrier method during sexual contact

what is TMV?

a virus that affects many species of plants like tomatoes

what are TMV symptoms?

mosaic like pattern and discolouration on the leaves of the plants

what are continuous complications of TMV?

the discolouration on leaves lead to less chlorophyll to carry out photosynthesis, which leads to stunted growth

what is an example of a fungal disease?

rose black spot

what are rose black spot symptoms?

causes purple/ black spots to form on the leaves of roses

what are further complications of rose black spot?

the leaves can turn yellow and fall off as there isnt enough chlorophyll to carry out photosynthesis. This stunts growth and makes roses less attractive for pollinators

what is rose black spot spread from?

water or the wind

how is rose black spot treated?

using fungicides or killing off the diseased leaves on the plant so the fungus cant spread to other roses

what is an example of a disease caused by a protist?

malaria

how is malaria spread?

via mosquitos (the anopheles). They’re vectors which pick up the malarial protist and spreading it between an infected animal and the next animal it feeds on by inserting the protist into the animal’s blood vessels

what are symptoms of malaria?

bad headaches and fever

what are further complications of malaria?

can be fatal. the protist goes to the liver, bursting the cells, including red blood cells, causing fatigue

how is malaria prevented?

destroy breeding site to stop vectors from spreading protists, using mosquito repellent, and mosquito swatters

what are some bacterial disease examples?

salmonella, gonorrhoea

how is salmonella spread?

by eating food thats been contaminated with salmonella bacteria, like eating food prepared in unhygienic conditions or eating raw chicken

what are salmonella symptoms?

fever, stomach cramps, vomiting, diarrhoea

where can salmonella bacteria be found?

the guts of many animals, raw meat, poultry, and eggs

who can be affected by salmonella fatally?

the pregnant, young children, and the elderly, because you are losing a lot of water with salmonella poisoning

how is salmonella treated?

antibiotics, or just letting it pass through the body

how is salmonella prevented?

cooking in hygienic conditions, poultry being vaccinated, cooking chicken properly

what is gonorrhoea?

a sexually transmitted disease

what is gonorrhoea spread by?

unprotected sexual contact with an infected person

what are symptoms of gonorrhoea?

pain when urinating, thick green/ yellow discharge from vagina or penis

what are further complications of gonorrhoea?

untreated can cause long term pelvic pain, infertility, or ectopic pregnancies

how is gonorrhoea prevented and treated?

treated with antibiotics and prevented using the barrier method with sexual contact and limiting sexual partners

how do you prevent the spread of disease? (4)

• being hygienic

• destroying vectors

• isolating infected individuals

• vaccinations

how do you stay hygienic?

washing hands thoroughly before preparing food or after sneezing

how does destroying vectors prevent disease?

as getting rid of the organisms that spread disease can prevent the disease being passed on

how can vectors be destroyed?

using insecticides, or destroying their habitat site so they can no longer breed

how does isolating infected individuals prevent disease?

prevents the individual from passing it on to anyone else

how do vaccinations prevent disease?

vaccinating people and animals against communicable diseases means they cant develop the infection and pass it on to others

what does the skin do to prevent disease?

acts as a barrier to pathogens. It also secretes antimicrobial substances which kill pathogens

what does hair and mucus in the nose do to prevent disease?

they trap particles that could contain pathogens

what does the trachea and bronchi do to prevent disease?

secretes mucus to trap pathogens. they are lined with cilia (hair like structures), which waft the mucus up to the back of the throat where it can be swallowed

what does the stomach do to prevent disease?

produces hydrochloric acid, which kills pathogens that make it that far from the mouth

how does the immune system attack pathogens?

with white blood cells. They travel around in the blood and crawl around you patrolling for microbes.

whats the 3 ways white blood cells attack disease?

1. phagocytosis→ engulfing foreign cells and digesting them

2. producing antitoxins→ counteract toxins

3. producing antibodies

how do white blood cells produce antibodies? (4)

1. every invading pathogen has unique molecules (antigens) on its surface

2. when some types of white blood cells come across foreign antigens, they will produce proteins called antibodies

3. antibodies lock onto the invading cells, acting as a signal so they can be found and destroyed by other white blood cells.

4. each antibody is complementary to a specific antigen

what happens after producing antibodies?

more antibodies are then produced rapidly and carried around the body to find similar bacteria/ viruses

what are vaccinations?

injecting small amounts of dead/ inactive pathogens. These carry antigens, which cause your body to produce antibodies to attack them, even though the pathogen is harmless (since dead/inactive)

what does the MMR vaccine contain?

weakened versions of the viruses that cause measles, mumps, and rubella (German measles) all in one vaccine

why are vaccinations good?

because if live pathogens of the same type appear after that, the white blood cells can rapidly mass produce antibodies to kill of the pathogen

what are pros of vaccines?

1. have helped eradicate lots of communicable diseases that were once common in the UK

2. herd immunity

3. epidemics (big outbreaks of disease) can be prevented if a big % of the population is vaccinated

what are cons of vaccines?

1. vaccines dont always work, sometimes they dont give you immunity

2. you can sometimes have a bad reaction to a vaccine (eg. swelling, fever, possibly seizures), despite being rare

what are painkillers?

drugs that relieve your symptoms but don’t actually kill the pathogens

what do antibiotics do?

kill or prevent the growth of the bacteria causing the problem without killing your own body cells

why should you make sure you get the right kind of antibiotics?

because different antibiotics kill different types of bacteria

why dont antibiotics or drugs kill viruses?

because viruses reproduce using your own body cells which makes it hard to develop drugs that destroy just the virus and not your body cells

what can some bacteria do that make them resistant to antibiotics?

mutate

when might some bacteria be resistant to antibiotics?

with an infection

what happens when you treat an infection?

only the non resistant strains of bacteria will be killed

what happens to the resistant bacteria?

it will survive and reproduce, and the population of the resistant strain will increase. This is an example of natural selection

what could the resistant strain cause?

a serious infection that cant be treated via antibiotics

what can be done to slow down the rate of development of resistant strains?

doctors avoid over prescribing antibiotics. They only prescribe them for more serious things.

what do the chemicals plants produce defend them from?

pests and pathogens. They can also be used for treating human diseases and relieving symptoms

what were a lot of current drugs discovered from?

studying plants used in traditional cures, eg. aspirin from willow plants and digitalis from foxglove leaves, or via extraction from microorganisms, eg. penicillin

how are drugs made these days?

in large scales in the pharmaceutical industry - they are synthesised by chemists in labs

what happens in preclinical testing?

the process when drugs are tested on human cells and tissues in a lab

when cant you use human cells and tissues to test drugs?

when the drug affects whole or multiple body systems eg. a drug test for blood pressure has to be done on a whole animal because it has an intact circulatory system

what is the step for testing drugs after preclinical testing?

testing on live animals

what is testing on live animals fro?

to test efficacy, toxicity, and the best dosage

what is efficacy?

whether the drug works and produces the effect you’re looking for

what is toxicity?

how harmful the drug is

what does the best dosage include?

the concentration that should be given, and how often it should be given

what is the first step of a clinical trial?

the drug is tested on healthy volunteers to make sure it doesnt have any harmful side effects. it will begin at a very low dose and be gradually increased