Biology-Year 9-Communicable Diseases

Physical = the bodies ability to function e.g. diet, sleep, alcohol, weight & exercise.

Mental = How we feel, think and cope with life e.g. thoughts, stress, learning dissorders & mental illness.

Social = How we react with people in environments e.g. friends, relationships & communication 

Health is not only about not having an illness or infection, but our mental health and whether we have enough interractions with other people.

We display this in a triangle with one of the health factors on each side.

Commmunicable:

• It can be passed on from person to person.
• Infectious and are caused by pathogens.
• Likely to be acute. Develops quickly.
• Flu, Chicken poxs, Ebola

Non-Communicable:

• It is in one person and can't be passed on.
• Can be caused by lifestyle choices such as smoking, alcohol abuse, diet and drugs.
• Causes 60% of deaths worldwide.
• The 4 types of non-communicable diseases are cancer, diabetes, cardiovascular disease and infectious diseases of the respiratory system.
• Tend to be chronic, long lasting and progress slowly.

Both often require medication but non-communicable can also require a lifestyle change. They require different treatments, prevention and control methods.

There are 4 types of pathogens: fungi, bacteria, viruses and protoctist.

Bacteria:

• Cholera, TB, Food-poisoning.
• Passed on via water or air (sneezes or coughs), Vectors, Food (salmonella).

Fungi:

• Athletes foot.
• Passed on by contact on moist surfaces.

Viruses:

• Influenza, Mumps, AIDs, Measles.
• Passed on in the air, sexual contact, exchange of body fluids (needles).

Vectors (houseflies, mosquitos) can pass on diseases by putting pathogens into human blood or on other objects.

Fungi & Bacteria Cells.

Virus:

• Has genetic material (DNA and RNA)
• Capsid
• Tail fibers 

Prokaryotic Cell (bacteria):

• Can reproduce without a host
• Has genetic material
• Has a cell membrane

Eukaryotic Cell (our cells and viruses):

• Can reproduce without a host
• Has genetic material
• Membrane-bound organelles
• Cell membrane
• Nucleus

A virus replicates only inside the living cells of other organisms. They can infect infect all forms of life: animals, plants and bacteria.

The capsid is the outside that protects the genetic material.Thegenetic material give instructions to the host. The tail fibers are at the bottom and they attach to the host cell.

Adsorption -> Entry -> Replication -> Assembly -> Release

Attachment -> Entry (injecting DNA/RNA) -> Replication -> Release 

Virus attaches to the host cell.

The virus injects its genetic material into the host cell.

The genetic information recruits the host cell's enzymes.

The enzymes make the parts for the new virus cells.

The new vrius cells assemble.

They break free from the host and the new virus cells go on to infect other body cells.

This cycle is shorter and quicker than the lysogenic cycle but is less sneaky, however they bothe do the same thing in the end.

The viruses herpes and HIV use the Lysogenic cycle.

Instead of the viruse cell reproducing straight away in the host cell, the virus mixes the DNA or RNA with the actual host cells genome (DNA) this means that when the cell reproduces it also reproduces all the viruses DNA.

However the new virus cells do not form at this point

The host cell will reproduce lots of times without the viruse DNA doing anything, because the virus is dormant in the host cell for years and years and then come up much later on in life, this can sometimes happen with STIs.

Eventually there is a trigger (a chemical that becomes present) and then the genetic material to leave the genome and begin the lytic cycle.

It is a lot longer than the Lytic cycle but a lot more dangerous as someone will not notice they have the virus (HIV) and they could pass it on, not try to get treatment and all in the meantime the virus becomes more severe.

Viruses:

• Has a protein coat, which surrounds the DNA/RNA.
• No cytoplasm or nucleus.
• Contains DNA/RNA.
• Only reproduces in living host cells - they are parasitic.
• 0.01 to 0.1 μm

Bacteria:

• Has a cell wall made of carbohydrates and proteins.
• Has cytoplasm and DNA, in circular chromosomes.
• Some of them even have small plasmids.
• No nucleus.
• Some have slime capsules, flagellum for movement.
• Photosythesise
• 1.5 μm

Protoctists:

• Single celled and multicellular.
• Has a cell wall, cytoplasm and nucleus.
• Contains DNA.
• Photosynthesise.
• They are animal like cells and they feed on dead or living tissue.

Fungi:

• Single celled and multicellular.
• Has a cell wall made of the same material found in insect's exoskeletons.
• Has cytoplasm and DNA.
• Does not photosynthesise.
• Has many nuclei (hyphae) in the cytoplasm and it is not divides into separate cells.
• Multicellular fungi have mycelium (group of thread like hyphae).
• They feed by extracellular digestion - saprophytic.
• 40 μm to 400 μm

These infections are passed on from person to person when having sex. Both men and women can pass on STIs and there are several types of them.

Bacteria: Chlamydia, Gonorrhoea, Syphilis, Vaginosis

Viruses: Herpes, HIV, Pubic Warts

Parasites: Pubic Lice

Fungi: Thrush

These are not always sexually transmitted because they can be developed in other ways otehr than sexual contact.

Physical Barriers:

Most plants have waxy cuticles to prevent pethogens entering and pests damaging them. It also prevents water collecting on the plant and this lowers the chance of pathogens getting to the plant which are transfered by water. 

Each cell is surrounded in a cell wall made of cellulose. 

Chemical Barriers:

They produce lots of different chemicals called antiseptics these kill bacterial and fungal pathogens. They also produce chemicals that deter pests from feeding on their leaves.

Some of these chemicals can be used as drugs to treat human diseases or relieve symptoms: Quinine was used to treat malaria & Asprin is used to relieve pain and fevers.

How do disease organisms enter the body?

• Dust and the rubbing of the eyes
• Breathing in infected water droplets 
• Using contaminated needles or blood transfusion
• Through scratches and cuts
• Animal or insect bites
• Sexual activity
• Direct penetration of the skin
• Contaminated food, drink, hands and utensils.

Chemical Barriers:

• Tears - contain emzymes/lysozyme that kill bacteria.
• Mucus - Found in the nose and air passages.
• Blood - Contains platelets and fibrinogen which begin clotting to provet pathogens entering wounds. There are also white blood cells in the blood the produce antibodies.
• Secretion - found in the vagina is mildly antiseptic.
• Stomach acid - hydrochloric acid kills bacteria in digested food.
• Ear wax - is midly antiseptic.

Physical Barriers:

• Ear wax 
• Nostril hairs
• Cilia - found in the bronchi and trachea and they are hair like structures.
• Skin 
• Mucus

Bacteria is cultured in growth medium (e.g. agar jelly, nutrient broth solution) and these contain carbohydrates, minerals, proteins and vitamins that the bacteria needs to grow.

At school the cultures must be kept at 25°C in the incubators, as harmful pathogens form more rapidly at higher temperatures. In real labs they will incubate the bacteria at higher temperatures to provide the optimum conditions for growth.

Inoculating loops are used to transfer microorganisms to the agar jelly or you can use a sterile dropping pipette and a spreader.

Aseptic Techniques: techniques that prevent the contamination from microorganisms.

• Sterilised Petri dish & Sterilised Inoculating loop via passing it through a hot flame.
• Lids should only briefly be removed when transferring bacteria.
• Covering the dish with a lid that is lightly taped on, prevents bacteria from the air getting in. It should be stored upside-down to stop condensation falling on the agar.

Place paper discs soaked in different antiseptics or antibiotics (as well as one with anything on it to be the control) onto an agar plate, that has an even coverage of bacteria (agar is used because it provides food and nutrience for the bacteria). Leave some room between each disc.

The antibiotic will diffuse into the jelly. Antibiotic-resistant bacteria will grow on the jelly around the paper disc because they are not affected by the antibiotics. But non-resistant strains will die beacuse they are killed by the antibiotics and therefore won't grow there, leaving a clear area on the agar jelly called the inhibition zone.

Leave the plate for 48 hours at 25°C.

To compare the effectiveness of the antibiotics, antiseptics or plant extracts you have to look at the relative sizes of the inhibition zones. The bigger the zone the more effective the substance was. You can do this by eye but the more accurate method is to find the area of the inhibition zones.

Area = πr²