Biology B10 and B14

two types of disease

Communicable (transmissible)

Non-communicable

communicable diseases

can be transferred from one person to another (infectious)

Non communicable

Cannot be transferred from one person to another

Examples of communicable diseases

Common cold, flu, COVID 19

Examples of non communicable diseases

Cardiovascular diseases, strokes, cancer (genetic diseases)

Cause of communicable diseases

Pathogens

Cause of non communicable diseases

Lifestyle and genetics

Pathogen definition

Microorganism or virus that can cause communicable disease.

Bacteria, Fungi, Protist viruses

2 types of cells

Prokaryotic: simple cells without a nucleus and with membrane bound organelles

Eukaryotic: complex cells with a nucleus and membrane bound organelles

Bacteria and examples

Single-celled prokaryotic microorganisms, some of which are pathogenic in humans, animals and plants.

Eg. Salmonella

Fungi and examples

A large group of eukaryotic organisms that contain single-celled and multicellular organisms, some of which are pathogenic in humans, animals and plants.

Eg. Trichophyton (athletes foot)

Protists and examples

A eukaryotic, usually single-celled organism of the kingdom Protista, some of which are pathogenic in humans, animals and plants.

eg. Plasmodium (malaria)

Viruses and examples

An ultramicroscopic infectious agent that can only reproduce inside the cells of living hosts, with negative consequences.

Constructed of a protein shell surrounding genetic material. Biologists do not consider this type of pathogen to be alive.

eg. HIV, COVID 19

Some bacteria have a slime capsule. What might bacteria use a slime capsule for?

Protective outer layer that stops the cell from drying out. It is also to shield them from harmful substances. Additionally, it can help them adhere to surfaces for colonisation.  

Why are viruses not considered a living organism? (Think about MRS GREN and cell structure)

They do not carry out the seven life processes 

They do not have a typical cell structure

• Protein shell

Influenza virus

Cold/ flu symptoms

HIV

Destroys white blood cells. The body cannot defend itself from other pathogens, leading to infections that result in AIDS

How can a pathogen be transmitted

• Direct contact: physical contact with an infected individual, such as through direct touching, blood transfusions, or sexual intercourse.

• Indirect contact: contact with a contaminated object or surface that carries the pathogen, such as touching contaminated surfaces, eating contaminated food, animals, breathing in contaminated air, sharing towels or clothes

Methods to control spread of disease

• Clean water supply ensures water is free from pathogens which prevents waterborne diseases like cholera

• Hygienic food prep such as washing hands with soap, correct food cooking methods clean area prevents contamination of food.

• Good personal hygiene such as washing hands with soap, using tissues to sneeze and cough and disposing them reduces transmission of diseases

• Waste disposal reduces prevalence of pests that can act as vectors for transmissible diseases

• Sewage treatment removes harmful pathogens from waste before releasing it into environment. Reduces spread of disease in water.

Antigens

how does our body protect itself from pathogens?

All cells have their specific antigens on their surface. Since our body recognises “self antigens” by shape, foreign shaped antigens trigger an immune response where the white blood cells would try to engulf or destroy the pathogen.

Non specific barriers

• Skin (platelets, sebaceous glands, skin flora)

• Nose hair

• Lashes

• Mucus

• Cilia (found in trachea and waves side to side to move mucus and pathogens towards the stomach)

Chemical barriers

• Stomach acid: hydrochloric acid of pH 2 which denatures pathogen enzymes

• Lysozymes: made in tears prevents eye infections, destroys bacteria cell walls

How do the cilia protect the lungs and airways from pathogens

They sweep trapped pathogens out of the trachea to be swallowed in the stomach. 

Phagocytes - NON-SPECIFIC

• Phagocytes engulf and destroy pathogens such as bacteria.

• A phagocyte surrounds the bacterial cell, enclosing it in a vacuole

• Enzymes are secreted into the vacuole to destroy the bacterial cell

• The process of engulfing the pathogen is called phagocytosis.

Lymphocytes - SPECIFIC

• Lymphocytes make antibodies: small proteins that attach to and destroy specific pathogens.

• Antibodies recognise specific antigens which are proteins on the surface of pathogens

• Lymphocytes can also form memory cells which remember specific pathogens so if we are infected again by the same pathogen we can destroy them faster. This is immunity.

Active immunity

defence against a pathogen by antibody production in the body

Gained after an infection by a pathogen or vaccination

Vaccines

Vaccines allow a dead or altered form of the disease-causing pathogen (or their antigens) to be introduced into the body. 

The weakened version will not cause the disease in the person receiving the vaccine, but it will prompt their immune system to respond much as it would have on its first reaction to the actual pathogen. 

Explain vaccination

During vaccination, a dead or weakened version of the pathogen is injected in the body. Thus, lymphocytes produce antibodies in response to the pathogen, leading to a rise in antibody levels. Over time, the levels decrease but some create memory cells to protect the body. 

If exposed to the same pathogen, the memory cells are able to quickly produce the specific antibodies, resulting in a quicker and larger increase in antibody levels. This is active immunity. 

Herd immunity

Since not everyone can be vaccinated, eg people with underlying health conditions or who have severe allergies to some vaccine components. 

These people can still be protected if they live in and amongst others who are vaccinated. When a lot of people in a community are vaccinated the pathogen struggles to circulate because most of the people it encounters are immune.

Drug definition

Any substance taken into the body that modifies or affects chemical reactions in the body.

Which part of a bacterial cell do antibiotics destroy/disrupt?

Cell wall

Why is penicillin not harmful to human (or other animal) cells?

Animal cells do not have cell walls

Antibiotic definition and limitation

substances that slow down or stop the growth of bacteria, curing a disease caused by a bacterial pathogen.

It only can be used to treat bacterial infections, not all are effective against many bacteria types

Why are antibiotics not used to treat diseases caused by viruses?

Antibiotics specifically target bacterial structures such as breaking down the cell wall. However, viruses are not cells and have their own mechanism, making antibiotics useless against viruses.

Antibiotic resistance reasons

• misuse and overuse of antibiotics

• failure to complete the fully prescribed course by a doctor

• use of antibiotics in farming

Result of antibiotic resistance

These can lead to the effectiveness of antibiotics being reduced, and the incidence of antibiotic resistance increasing. These bacteria are commonly known as superbugs.

Antibiotic resistant bacteria are dangerous since it will lead to a spread of infections we are unable to control

Process of antibiotic resistance

A random mutation occurs in the DNA of individual bacterial cells.

The mutation protects the bacterial cell from the effects of the antibiotic - it becomes antibiotic resistant

Bacteria without the mutation die when the antibiotic is present

Antibiotic resistant bacteria survive and can reproduce with less competition from non-resistant bacterial strains

The genes for antibiotic resistance are passed to the offspring

Over time the whole population of bacteria becomes antibiotic resistant because the antibiotic resistant bacteria are best suited to their environment