7.1

pathogens

disease-causing organisms

communicable / infectious diseases/ transmissible diseases

diseases that can spread from one person to another

what are the most common pathogens that effect the human body

bacteria and viruses although fungi and animal parasites can also be involved

what are bacteria

prokaryote, unicellular organisms with a simple internal structure

structure of bacteria

lack a nucleus, DNA floats freely in cytoplasm, or in the form of circular plasmids

in what form does DNA exist in bacteria

may float freely in cytoplasm, or it may be in the form of circular plasmids

is all bacteria harmful

no, most bacteria is harmless to our body and is actually essential to break down of organic material and cycling of elements

what are 4 types of bacteria

cocci, bacilli, spirilla, vibrio

cocci

spherical cells, that may exist singularly or in pairs or clusters

bacilli

with flagella

sprillia

twisted cells

vibrio

like curved rods, often shaped like a comma

how can we identify a bacetrium

we must first grow it on an agar plate or growth medium in specific conditions, then only it can be stained and viewed under a microscope

what can viruses be visible under

too small to be seen with a light microscope, must be viewed under an electron microscope

are most viruses harmless like bacteria

most viruses are harmful like HIV

what were all viruses found to contain

all were found to contain genetic material in the form of DNA or RNA but never both

what is the molecule of DNA or RNA surrounded by

by a protective coating and some even have an external lipid envelope

are viruses considered to be living things

no, viruses are not living things, they cant reproduce by themselves.

because they cant reproduce, instead what do they do

instead, they infect a living cell and its DNA or RNA induces the cell to manufacture more virus particles of the viral DNA/RNA

briefly outline the process of viruses infecting other cells

1. injects DNA or RNA into host cell
2. causing the cell to manufacture more virus particles
3. virus particles leave the host cell and infect other cells
4. during the process, the host cell is left damaged or dead or changed

why do symptoms differ for viruses

because viruses differ in the type of cell they invade, therefore the symptoms shown relate to the tissue that is affected

bacteriophages

some viruses affect bacterial cells, resulting in the death of the bacterium. such viruses are called bacteriophages.

what are the two ways in which pathogens may be transmitted

\-direct/indirect contact

direct contact trasnmission

occurs when there is a physical contact between an infected person and susceptible person

indirect constant transmission

when there is no direct human-human contact

how does contact occur in indirect contact transmission

contact occurs from a reservoir to contaminated surfaces or objects

how do direct contact infections spread

occur when disease causing microorganisms pass from infected person to healthy person via direct physical contact with blood or bodily fluids

examples of direct contact

touching, kissing, sexual contact, oral secretions, or contact with body lesions

how do indirect contact infections spread

spread when an infected person sneezes of coughs, sending infectious droplets into the air

transmission by contact

involves spread of pathogen by direct physical contact, may be direct eg, person touching person or indirect, person touching object, person touches object

ingestion

of food or drink contaminated with pathogens results in disease. eg salmonella

transfer of bodily fluids

when blood or bodily fluids comes in contact mucous membranes such as mouth, nose, genitilia or throat or it enters the bloodstream through a needle or break in the skin then pathogens may enter the body of that person

transmission by droplets

may occur when tiny droplets containing the pathogenic organisms are emitted when talking, coughing, sneezing or breathing, these droplets may be inhaled by others or land on food or drink, infecting it, eg COVID 19

airborne transmission

moisture in inhaled droplets evaporates, most the bacteria dies however some still remains, these remain viable for a longer distance than droplets . eg measles

transmission by vectors

transfer of pathogens by other animals such as mosquitos and insects. eg malaria and dengue fever spread thru mosquitoes and bubonic plague through mice