Biology paper 1 - infection and response

How does a vaccine work to protect people

vaccines contain a dead or inactive form of the pathogen = the pathogen in vaccine cannot cause disease. When injected , the white blood cells are stimulated to produce antibodies against the dead or inactive pathogen. At the same time. The white blood cell divides by mitosis to produce a lot of copies of itself - these copies of white blood cells can stay in the blood for decades. If the same pathogen enters the body later, the white blood cells can produce the correct antibodies quickly = prevents infections.

What does a graph look like when a vaccine is injected into a person’s body - include the amount of antibody and the time after vaccine is injected

The graph typically shows an initial delay before antibodies are produced, followed by a steep rise in antibody levels as the immune system responds. After reaching a peak, antibody levels gradually decline but can remain elevated for a long period, demonstrating immunological memory.

What is herd immunity

Herd immunity is a form of indirect protection from infectious diseases that occurs when a significant percentage of a population becomes immune, either through vaccination or previous infections, thereby reducing the spread of disease and protecting those who are not immune.

How are most disease caused by

bacteria eg salmonella poisoning / gonorrhoea

When was penicillin first discovered

1940s

what is an advantage of antibiotics

can kill infective bacteria inside the human without harming body cells

what is antibiotic resistance

the ability of bacteria to survive and grow despite the presence of an antibiotic, making treatments ineffective.

why does antibiotic resistance occur

Antibiotic resistance occurs due to mutations in bacteria or by the overuse or misuse of antibiotics, leading to the bacteria being able to evolve and survive

what pathogen can antibiotics not kill

Viruses eg coldsand the flu.

What is the job of painkillers

to treat the symptoms of a disease by relieving pain HOWEVER they do not kill pathogens

why is it important for specific antibiotics to treat specific bacteria

Because different bacteria have unique structures and mechanisms that may only respond to certain antibiotics

Why is it difficult to develop drugs to kill viruses

Because viruses live and reproduce inside human cells, making it challenging to target them without harming and damaging body’s tissues.

What are pathogens and give examples of main pathogens

Microorganisms that cause infectious disease eg bacteria , viruses , protists , fungi

How can bacteria make people ill

Once inside the human body, bacteria reproduce very rapidly, bacteria can then release harmful toxins and toxins damage tissues = making us ill

Can viruses reproduce by themselves - if not where do they reproduce

viruses cannot reproduce by themselves - they can only reproduce inside a host cells

How does the virus damage cells

The virus enters host cells by invading the host cell, the virus now reproduces inside the host cell , this is very damaging to the cell when the virus leaves the cell and can cause the cell to burst open and die

how are pathogens spread

spread in the air eg in water droplets eg influenza virus

Spread directly in water eg cholera

By direct contact between individuals eg HIV

What are the ways that pathogen spread is reduced

basic hygiene practices eg washing hands

Providing people with clean drinking water Eg most drinking water contains chlorine = kills microbes

Use of condoms during sexual intercourse = reduces the spread of HIV

vaccination,

Isolation = prevents the pathogen from spreading to other people

safe food handling. - keep raw food away from cooked

What is a communicable disease

Disease that can be spread from person to person

How are communicable disease spread

By pathogens eg bacteria reproduce very/ viruses

What are non - communicable disease

diseases that cannot be spread from person to person.

What is the definition of health

Defined as the state of physical and mental well- being

What are the ways that ill health can be caused by

communicable disease , non communicable disease , poor diet , high stress , working with harmful chemicals

Why are people with defective immune systems more likely to suffer from infectious disease

People with defective immune systems have a reduced ability to fight off pathogens, making them more susceptible to infections.

How are most cervical cancers caused by

the human papillomavirus (HPV), which is a sexually transmitted infection that can lead to abnormal cell growth and infection in cells of cervix

What virus can be produced as a result of HPV

cervical cancer and other related cancers in the reproductive system.

How is an allergy produced

when a disease is triggered by the immune system - the body is infected with a pathogen which the immune system fights off but the person is left with an allergy

What are two examples of viruses

Measles and HIV

What is measles and what are the symptoms

Measles is a highly contagious viral infection

symptoms such as high fever, cough, runny nose, and a distinctive red rash that usually appears several days after the initial symptoms.

how is measles virus spread

Spread in droplets when an infected person coughs or sneezes, the virus then passes into a different person when these droplets are inhaled

What are some risks of measles virus

can cause complications eg damage to the breathing system and the brain and can be fatal , this is why most children are vaccinated against measles at very young age

What are the symptoms of HIV and how can develop into AIDS

flu - like illness but this disappears after few weeks, at this point the virus is attacking the cells of the patient’s immune system, over time the immune system gets severely damaged and therefore cannot fight off other infections as easily and the damaged immune system is also unable to fight off cancer cells - when the immune system reaches this highly damaged stage, the patient can now easily contract other infections eg TB and the patients may also develop cancer. At this point the patient is described as having late stage HIV / AIDS and the disease at this stage is fatal

How can people with HIV be treated

using Antiretroviral drugs which stop the virus from multiplying inside the patient so the virus doesn’t damage the patient’s immune system. Patients who take antiretroviral drugs don’t go onto developing AIDS and can lead a normal life expectancy

What is an issue with the antiretroviral drugs

they are not a cure for HIV or AIDS and the patients must take the drugs for the rest of their life

how is HIV transmitted

through the exchange of fluids between humans - spread by unprotected sexual intercourse

Spread by infected needles between drug users

How can HIV be shared through needles

When infected needles are reused, blood containing HIV can enter the bloodstream of another person, facilitating transmission.

What type of pathogen can be killed by antibiotics

Bacteria, but not viruses.

Is salmonella communicable or non communicable

communicable

what are examples of communicable diseases

influenza, tuberculosis, and HIV, salmonella , gonorrhoea , malaria

how is the salmonella bacteria spread

Salmonella bacteria are spread primarily through contaminated food and water, particularly undercooked poultry and eggs. and ingesting these contaminated food

how does salmonella bacteria cause illness

the bacteria secretes harmful toxins and cause the symptoms of salmonella

What are the symptoms of salmonella

Fever , abdominal cramping, vomiting , diarrhoe

how can the spread of salmonella be controlled

vaccinated / killing infected poultry eg chickens

Sterilising surfaces

Separating cooked food with raw food

Washing hands after being in contact with raw food

Cook food thoroughly

What is gonorrhoea

a sexually transmitted disease

What are the symptoms of gonorrhoea

thick, yellow / green discharge from penis / vagina

Pain when urinating

How the spread of gonorrhoea be stopped

using condom during sexual intercourse to stop the bacteria passing from person to person

People who have unprotected sex should be tested for gonorrhoea - they can then be treated with antibiotics to kill the bacteria before they pass it onto another person

What pathogen is malaria disease

Protist

Describe the life cycle of malaria

person infected with malaria → first the infected person is bitten by a mosquito, the malaria pathogen passes into the mosquito → the mosquito now bites a different person and passes the malaria pathogen to them

How is malaria spread

spread through a vector ( mosquito )

How can the spread of malaria be prevented

stop mosquito breeding → mosquitos breed in still water, so to stop mosquito breeding, areas of still water need to be drained

Spray areas of still water with insecticide which kills mosquitoes

Use a mosquito net to prevent mosquitoes from biting humans → you can also spray mosquito net with insecticides which will kill any mosquito landing on the net

Ising antimalarial drugs

Malaria vaccines

What is TMV

widespread plant infection and can affect crop yields

what are the symptoms of TMV and what are the effects of theses symptoms

Discolouration in a mosaic pattern → because of this discolouration rate of photosynthesis is reduced = growth of plant is also reduced

what is rose black spotw

plant disease caused by a fungus

What are the symptoms of rose black spot and what are the effects of these symptoms

Rounded purple or black spots on leaves, leading to yellowing and leaf drop. → causes the rate of photosynthesis to fall which reduces rate of growth

how is rose black spot fungus spread

by water or wind

How to treat rose black spot

using fungicides and removing infected leaves and destroying them

How is TMV spread

TMV is spread through contact with infected plants, contaminated tools, or by insects.

How is TMV treated

There is no treatment however you can destroy and remove infected plants to stop spreading the TMV

What type of insects can attack plants

aphids

How do aphids damage plants

Aphids damage plants by extracting nutrients such as sugars and they extract the amino acids which are required to help with growth , which can weaken the plant, lead to stunted growth, and transmit viruses.

Why are insects not classed as a pathogen

because they do not directly cause disease; rather, they can damage plants and transmit pathogens.

What are symptoms plant diseases

Visual inspection eg discolouration , spot on leaves , stunted growth, decay / rot , growths , malformed stems / leaves

How can you identify plant diseases

using a garden manual or website

Take the infected plant to a lab to identify the pathogen

Use testing kits containing monoclonal antibodies

What are the two plant ion deficiencies

Nitrogen and Magnesium ( nitrate ion and magnesium ions )

What are the consequences of nitrate ion deficiencies and why

✅ Step 1 — Link nitrates to protein synthesis:
Nitrate ions are absorbed from the soil and are needed to make amino acids.

✅ Step 2 — Link amino acids to proteins:
Amino acids are used to build proteins, which are essential for cell growth and repair.

✅ Step 3 — Link lack of nitrates to less protein and reduced growth:
If a plant has a nitrate deficiency, it cannot make enough amino acids → fewer proteins are produced → less cell division and less growth → the plant becomes stunted.

✅ Step 4 — Add extra mark for leaf symptoms (if asked):
Because nitrates are mobile in the plant, they are moved from older to younger leaves, so older leaves turn yellow.

what are the consequences of magnesium ion deficiencies

✅ Step 1 — Link magnesium to photosynthesis:
Magnesium ions are needed to make chlorophyll. → magnesium deficiency leads to condition called chlorosis

✅ Step 2 — Link chlorophyll to glucose production:
Chlorophyll is essential for absorbing light energy in photosynthesis, so if there’s a magnesium deficiency, the plant makes less chlorophyll → photosynthesis rate decreases → less glucose is produced.

✅ Step 3 — Link glucose to growth materials and energy:
Glucose is used in respiration to release energy for cell division, and it is also used to make cellulose for cell walls, amino acids for protein synthesis, and lipids.

✅ Step 4 — Link lack of glucose to reduced growth:
With less glucose, there is less energy and fewer materials available for growth, so the plant shows stunted growth.

What are the physical defence systems in plants

physical responses → all plants have a cellulose cell wall = difficult for microorganisms such as bacteria to penetrate.

Leaves are covered with a thin oily layer ( waxy cuticle ) → the waxy cuticle makes it difficult for microorganisms to penetrate which protects the plant from attack

Bark → barrier to entry by microorganisms, as bark ages it eventually falls off and is replaced with fresh bark underneath

What are the chemical plant defence systems in plants

plants release antibacterial chemicals which kill bacteria and prevent them from attacking the plant

Plants can release poisons to deter herbivores from grazing on the plant

What are the mechanical plant defence systems in plants

sharp thorns → directly protect a plant from being eaten by herbivore will prick at the herbivore and

Some plants have hairs which irritate the mouth of the herbivores making the plant difficult to eat

Some plants have leaves which droop or curl when touched →it is thought that this defence can scare herbivores as they are not used to plants moving like this

Mimicry in plants eg white dead nettle looks like stinging nettle but has no sting → herbivores are less likely to eat white dead nettle as they can easily mistake it for a stinging nettle

What is the job of the non - specific defence systems

to prevent pathogens from entering the human body

What are the parts of the non specific defence system and how do they protect human body

skin → forms a protective layer covering the body , the outer layer of the skin consists of dead cells and makes its difficult for pathogens to penetrate, the skin also produces an oily substance called sebum which can kill bacteria. When the skin is damaged it can sometimes allow pathogen to enter, however to stop this, the skin scabs over to trap pathogens

Nostrils→ contains hairs and mucus which trap pathogens before they enter the breathing system

Trachea and bronchi→ covered with tiny hair like structures called cilia, cilia are covered in mucus which can trap pathogens, the cilia now wafts the mucus upwards towards the throat where it is swelled into the stomach

Stomach → stomach contains hydrochloride acid which kills pathogens before they make their way further down into digestive system

How does the immune system protect humans against pathogens

Thought process of phagocytosis → white blood cells can digest and destroy pathogens , the white blood cells detects chemical released from the pathogen and moves towards it, the white blood cells then ingests the pathogens. Now the white blood cell uses enzymes to destroy the pathogens

Making antibodies → antibodies are protein molecules produced by white blood cells, antibodies stick to pathogens and triggers the pathogens to be destroyed, antibodies are extremely specific and since the antibodies stay in blood for long time they can protects us in case we ever get infected again with same pathogen

Certain types of bacteria release toxins which can make you feel unwell, however white blood cells produce antitoxins which stick to toxin molecules and prevent them from damaging cells

What are the 2 main functions of the immune system

destroys pathogens and any toxins produced

Immune system protects us in case the same type of pathogens invades us in the future

Which plant was used to extract the heart drug digitalis

foxglove w=

which plant was used to extract aspirin

willow tree

Which scientist discovered penicillin

Alexander Fleming

Where was penicilin found

in a mold contaminated petri dish. - mould called pencicillium

O He found mould (Penicillium mould) on his culture plates, with clear rings

о

around the mould indicating there was no longer any bacteria there

He found that the mould was producing a substance called penicillin, which killed bacteria

What are the stages of drug testing

Preclinical testing → carried out on cells, tissues and live animals NOT ON HUMANS as the drug could be extremely toxic

Clinical testing → carried out on healthy volunteers with very low doses of drug - this is to check that the drug is safe in humans. If the drug is found to be safe

The drug is then tested on patients to find the optimal dose with fewest side effects

To test the efficiency of the drug, the patients are split into two separate groups, one with the placebo and the other receiving the drug - can either be single blind or double blind trial

What is a placebo

a tables or injection with no active drug in it

What happens in double blind trials

The test group receives the active drug and the placebo ( control ) group receive a dummy drugs that looks exactly like the test drug but has no active ingredient - neither the patients nor th doctors know which people are receiving the active drug and which are receiving the placebo

Why are double blind trials used

to stop bias in case the doctors pay closer attention to people receiving the active drug

What type of white blood cells produce antibodies

lymphocytes - they produce antibodies against anything that body detects as foreign eg antigens

How are monoclonal antibodies produced

and mouse is injected with an antigen, this stimulates the immune system to produce lymphocytes which will produces antibodies against the antigen, the lymphocytes can then be collected from the mouse. The lymphocytes are fused with tumour cells which can divide quickly to produce a hyridoma cell which is able to produce antibodies as well as divide quickly by mitosis. A single hybrids a cells is selected to produce the desired antibody, this hybrids a cells is now able to divide by mitosis to form a clone of identical hybridoma cells ( the antibodies produced from this clone of hybridoma cells are all identical) and so monoclonal antibodies are produced and are collected and purified

What are monoclonal antibodies produced from

a single clone of hybridoma cells produce- this means that monoclonal antibodies are specific to one binding site on one protein antigen

What is an advantage of monoclonal antibodies being specific to one binding site on an antigen

They target specific cells or pathogens, minimizing damage to healthy cells

What are the uses of monoclonal antibodies

Used for diagnosis eg in pregnancy kits

Used to measure levels of hormones in blood

To detect pathogens in blood

To locate / identify specific molecules inside a cell / tissue

Treating diseases

What are monoclonal antibodies used for in pregnancy testing

to detect a specific hormone - this hormone is produced by the placenta of the developing fetus

What are the advantages of having pregnancy tests based on monoclonal antibodies

they are cheap and easy to use the test is also highly accurate if used correctly

What are the advantages of using monoclonal antibodies to detect hormones / pathogens

monoclonal antibodies are completely specific to what we are looking for

How does the monoclonal antibody treat cancer

cancer cells undergo uncontrolled mitosis and spread around the body, scientists can make antibodies specific to cancer cells, we then attach a radioactive substance or a toxic drug to the antibody, when the antibody is injected into the blood, it attaches to the cancer cells so the radioactive substance or toxic drug stops the cancer cells from growing and dividing , and the antibody delivers the substance specifically to cancer cells without harming other cells in the body