GCSE Biology: B3 - Infection and Response

communicable diseases

a dsiease that can be spread between individuals either directly or indirectly

pathogen

microorganisms that cause infectious disease

toxin

harmful substance produced by living cells such as bacteria

vector

an organism that does not cause disease itself but spreads infection by conveying pathogens from one host to another

virus examples

HIV leading to aids, tobacco moscaic virus, measles

Bacteria examples

Salmonella, Gonorrhoea

Fungi examples

Athelete's foot, rose black spot

Protists examples

Malaria

How do pathogens make you ill

They sometimes produce toxins that can damage tissues or killing the cells

how do diseases spread from one person to another

- vectors (wind)

- contaminated water

- direct contact

- food

- sex

Virus

- much smaller than bacteria and fungi

- they move into cells and use biochemistry to make copies of itself

- this leads to the cell bursting and releasing all the copies into the bloodstream

- the damage and destruction of the cells makes the person feel ill

bacteria

- they multiple very quickly through binary fission

- they produce toxins which damages cells

protists

some are parasitic meaning they use humans and animals as their hosts. they live on and inside, causing damage

fungi

they can produce spores which can be spread to other organisms

how to limit spread of disease

- disinfectants

- removing vectors

- vaccination

Measles symptoms

fever, red rash, can lead to pneumonia, can be fatal, and blindness

how is measles spread

droplet infection, sneazes, coughs

how to prevent measles

vaccinations for young children can reduce transmission

HIV symptoms

flu like symptoms, then the virus attacks the immune system which leads to AIDS

HIV how is it spread

By sexual contact or exchange of bodily fluids such as blood

How to prevent HIV

using condoms, not sharing needles, Antiretroviral drugs (stop the virus from replicating in the body)

Tobacco mosaic Virus symptoms

discolouration of leaves, affected part of the leaf can't photosynthesise which results in the reduction of yield, stunted growth

How is tobacco mosaic virus spread

contact between infected and healthy plants, vectors such as insects

how to prevent tobacco mosaic virus

pest control, growing, tmv resistant strains

what is salmonella

bacterial disease that is spread by bacteria ingested in food and can cause fever, adbominal cramps, vomiting and diarrhoea

how to prevent salmonella

keeping raw meat away from cooked food, cook food thoroughly

rose black spot

a fungal disease where purple or black spots develop on leaves, which often turn yellow and drop early

how is rose black spot spread

pores of the fungus are spread by wind

how to prevent rose black spot

fungicides, pruning (have to be burnt)

symptoms of malaria

fevers, shaking (when the protists burst out of blood cells

how to spread malaria

vector is female mosquito. protists reproduce sexually. when mosquito punctures the skin to feed on blood, protists enter the human bloodsteam via the saliva

how to prevent malaria

insectide coated insect nets whilst sleeping, removing stagnant water to prevent the vectors from breeding, travellers taking antimaarial drugs to kill parasites that enter the blood

human defence systens

skin, nose, trachea, bronchi, stomach

the skin

acts as a physical barrier, produces antimicrobial secretions to kill pathogens, good microorganisms (skin flora) compete with the bad microorganisms for space and nutrients

the nose

has hairs and goblet cells produce mucus (sticky substance) which prevent particles from entering your lungs

the trachea and bronchi

secret mucus in order to trap pathogens, cilia (hair like structure on cells) beat to waft mucus upwards so it cna be swallowed

the stomach

produces hydrochloric acid that kills any pathogens in your mucus, food or drink

phagocytes

engulfs and consumes pathogens, it destroys the pathogens

lymphocytes

made in lymph nodes and produces antibodies. each pathogen has an antigen on the surface which has its own specific complementary antibody which it can bind to. Once they bind the pathogens start to clump together so it's easier for the phagocyte to engulf.

memory cells

if you become infected again with the same pathogen the specific complementery antibody will be produced at a faster rate.

antibodies

neutralise toxins released by pathogen by binding to them

herd immunity/community immunity

By immunising a large proportion of people, the spread of pathogen is reduced

What are vaccines

make someone immune to a certaine disease so they are protected. vaccines contain a dead or inactivated form of the pathogen. Stimulates white blood cells to produce antibodies complementary to the antigens of the pathogen.

advantages of vaccines

- they have eradicated many diseases so far

- epidemics (lots of cases in an area) can be prevented through her immunity

disadvantages of vaccines

- they are not always effective in providing immunity

- bad reactions (fevers) can occur in response to the vaccine

why cant antibiotics kill viruses

Viruses reproduce inside the cells so it is hard to kill them without damaging the cells of your body at the same time

painkillers

chemicals that relieve the symptoms but do not kill the pathogens (aspirin)

antibiotic example

penicillin

how does the body seals cuts

platelets in your blood set up a chain of events to form a blood blot. Blood clot dries to form a scab. Scab forms a seal over the cut which stops pathogens entering the body throughout the wound

symtpoms of an immune response

- coughing

- sneezing

- temperature

vaccination steps

- Take a pathogen weakened, inactive or a small part and inject it into our bodies to cause an immune response

- This causes your lymphocytes to produce anti-bodies which are made from proteins

- The body makes memory cells so we are immune

primary immune response

During a primary infection levels of antibodies slowly increase, peak at around ten days and then gradually decrease

This is what happens when someone is vaccinated with a weakened or inactive pathogen or when someone catches a disease for the very first time

Second Exposure

A second exposure to the antigen that was in the vaccine, or to the same pathogen that made the person ill before, causes the white blood cells to respond much more quickly this time, also more antibodies are produced than in the primary response.

The antibodies are produced so quickly by the memory cells that the pathogen is killed off before it can make the person ill. This is called being immune to a disease or having immunity

innate immunity

the body's first line of defence against harmful substances and it's present at birth and lasts a person's entire life

Acquired immunity

a type of immunity that develops when the body's immune system responds to a foreign substance or microorganism. There are two types:

Passive: receiving antibodies to a disease or toxin from another source. (placenta or breast milk)

Active: produce antibodies to fight a disease after exposure to it

how do antibiotics work

Kill infective bacteria inside the body

Breaks down the cell wall of bacteria (but not your own cells)

They make holes in the bacterial cell wall which causes the bacteria to burst.

superbug

mutations occur during reproduction which results the bacteria to resist th antibiotics. When these bacteria are exposed to antibiotics only the non resistant ones die. The resistant ones survive and reproduce meaning the population will increase. This means antibiotics will no longer work

what causes the resistance of a superbug

Overuse of antibiotics or using them incorrectly

Bacteria mutation

Antibiotics kill non-resistant strains

Resistant bacteria reproduce

Not finishing course

Given as preventative to animals or so they can grow faster

what do drugs need to be tested for

toxicity, efficiency, if they carry out their role, preclinical testing, clinical trials

drug testing flor chart

- what diseases to treat

- traditional remedies (natural things to treat it instead of drugs)

- drug synthesis (making the drug)

- preclinical trials (tests in the lab)

- animal testing

- clinical trials (using volunteers)

- drug released into market only after peer reviewed

models

- computer models/ tissue samples

- living animals (mice, fruitflies, zebra fish)

- living humans

- yeast

non human models

- computer can be programmed to try and predict what will happen when treatment is given to a disease. Results cannot be 100%

- tissues samples show the effect that the treatment has on a group of cells. These cells are alive but not part of a whole organism. we also needs to know if the medicine can reach the part of the body that it needs to

animal testing

most common mice, rats and fish are used to see how medicine affects a whole body and it can tell us about the toxicity and will indicate what dosage is necessary for humans.

disadvantages of animal testing

- expense

- time consuming

- ethical issues

- can't accurately predict what will happen in humans (92% drugs safe and effective in animal trials but fail in humans)

phases of clinical trials

- human trials (testing on volunteers with low dose to ensure no harmful side effects)

- testing on patients (to find the most effective dose)

- final testing and licensing

human models

small groups of humans are used as a model for other humans to predict the effects in everyone else. Some patients will receive the drug and some will receive a placebo (sugar pill)

immunity meaning

the body's ability to respond quickly to a pathogen after the body has been exposed to it for the first time

antigen

a protein on the surface of pathogens

blind trial

a trial where the patient doesnt know if they are taking the drug or placebo

double blind trial

a trial where neither the patient of the doctor giving them the medicine knows whether they are getting the real drug or placebo

placebo

a substance which is designed to be indestinguishable from a drug being tested but has ni actual effect on the patient

traditional remedies

chemicals that plants use to kill pests and pathogens can be used to treat symptoms or human diseases

aspirin used as a painkiller ( willow trees)

digitalis is used to treat heart problems (foxgloves)

penicillin

he grew mould on plates

found penicillium mould with clear rings around the mould indicating there was no longer bacteria there

formation of monoclonal antibodies

An antigen is injected into a mouse

The mouse produces lymphocytes, which produce antibodies specific to the antigen

they are combined with tumour cells to form a cell called hybridoma

the hybridoma can divide to produce clones of itself which all produce the same antibody

the antibodies are collected and purified

monoclonial antibody

antibodies produced from single clone of cells that are specific to one binding site on one protein antigen

hybridoma

Formed by combining a tumour cell with a lymphocyte

These cells divide by mitosis and produce large amount of specific antibodies

uses of monoclonal antibodies

- pregnancy tests

- measure levels of hormones or chemicals

- reasearch and treatment of diseases

pregnancy tests

a hormone called hCG (human chorionic gonadotrophin) is present in the urine of pregnant women

the first section of the pregnancy stick has mobile antibodies complementary to hCG hormone which are also attatched to the blue beads

the second section has stationary antibodies complementery to the hCG hormon which are stuck down on the stick

when they urinate on the first section, if hCG is present it binds to the mobile antibodies to form hCG complexes

they are carried in the flow of liquid to the second section where the stationary antibodies bind to the hCG complexes

as they each bound to a blue bead it results in a blue line

In labs to monitour and measure

measure and monitor levels of hormones or chemicals in the blood

monoclonal antibodies are modified so that they will bind to the molecule you are looking for

the antibodies are bound to a fluorescent dye

if the molecules are in the sample then the antibodies bind to it and the dry can be observed

e.g. screening donated blood for HIV infections

research to find or identify certain molecules on a cell or tissue

look for build up of fluorescence

treatment of disease

cancer cells have antigens on their cell membrane knows as markers which can be targeted.

how to treat cancer cells using monoclonal antibodies

producing monoclonal antibodies that bind to tumour markers in order to stimulate the immune system to attack the cell

using monoclonal antibodies to bind tp receptor sites on the cell surface membrane of cancer cells. this means growth stimulating molecules cannot bind, stopping the cell from dividing

using monoclonal antibodies to transport toxic drugs, chemicals or radioactive substances as they can only bind to cancer cells

advantages of using monoclonal antibodies

they only bind to specific cells, meaning healthy cells are unaffected

can be bound to almost any substance

we can now produce mouse-human hybrid cells to reduce the chance of triggering an immune response

disadvantages of using monoclonal antibodies

difficult to attatck monoclonal antibodies to drugs

expensive to develop

ethical issues

common signs of plant diseases

- stunted growth (nitrate deficiency)

- spots on leaves (rose black spot)

- areas of decay (rose black spot)

- abnormal growth (crown galls caused by bacterial infection)

- malformed stems or leaves (aphid infestation)

- discolouration (magnessium defficiency or tobacco mosaic virus)

- pests on leaves

how to identify the disease the plant has by..?

- gardening manual or website

- identifying the pathogen by oberserving the plant in a lab

- using monoclonal antibodies in testing to identify the pathogen

aphids

- they infest roses and tomatoes.

- They are found in large numbers on new shoots

- they suck sap.

- reduces that growth rate of plants and can eventually kill them.

- Aphids are eaten by ladybirds, so gardeners often try to cultivate these in their gardens as a natural way of reducing aphids.

nitrate deficiency

- stunts growth

- nitrate in soil converts sugars made in photosynthesis into proteins

- these proteins are needed for growth

magnesium deficiency

- can cause chlorosis

- magnesium is needed to make chlorophyll

- this pigment is green and vital for photosynthesis

- if less is being made then parts of the leaves appear green and yellow which is called chlorosis

physical defences

prevent invasian of microorganisms

tough waxy cuticle stop entry into leaves

cellulose cell walls form physical barrier into the cells

plants have layers of deal cells around stems (bark) which stops pathogens entering. The dead cels fall off with the pathogens

chemical defences

to deter predators or kill bacteria

poisons deter herbivores

e.g. foxgloves, tobacco plants

antibacterial compounds kill bacteria such as mint plant

mechanical defences

thorns and hairs make it difficult and painful for animals to eat them (but do not defend against insects)

some leaves can droop or curl when touched which allows them to move away and move insects off their leaves

mimicry to trick animals

some plants droop to look like unhealthy plants

plants can have patterns to look like butterfly eggs so butterflies don't lay eggs here because of competition

species from 'ice plant family' have a stone and pebble like appearance in order ro avoid predatation

antibiotics

medicines that help cure bacterial disease by killing infective bacteria inside the body

What is gonorrhoea

a sexually transmitted disease (STD) caused by a bacterium with symptoms of thick yellow or green discharge from the vagina or penis and pain whilst urinating

What is HIV

human immunodeficiency virus

an infectious virus that weakens the immune system and can lead to aids (acquired immunodeficiency syndrome)

what is malaria

a disease caused by a protist that causes recurrent episodes of fever can be fatal. enter red blood cells and damage them

non specific defence

general physical and chemical barries that defend the body against different pathogens

pathogen

microorganisms that can cause infectious diseases

vaccination

the process of introducing small quanities of dead or inactive forms of a pathogen into the body to stimulate the white blood cells to produce antibodies