Unit 12 A: Diseases and Infection
In this assignment I will discuss infectious diseases and non-infectious diseases. Infectious diseases
are caused by five main pathogens such as: bacteria, virus, fungi, protozoa and parasite. Whereas,
non-infectious diseases are caused by a number factors such as: diet, environment, genetics and
degeneration. Then I will write a case study about an example of an infectious disease, stating the
symptoms and how the pathogens cause the disease to progress over time and the affect it has on
organs in the body and body systems. Similarly, I will write a case study about a non- infectious
disease and how I will analyse the effects of it on the human body. An infectious disease is a
disorder caused by pathogens that live in our body, normally completely harmless (Mayo Clinic
2019). However, under a change of conditions, some can cause disease; a disease which can be
passed by contact. A non- infectious disease is a disease which cannot be spread with any contact
from neither a human nor an animal, so they aren’t caused by pathogens or cannot be spread by a
vector (Study.com 2019)
Bacteria:
The main features: Bacteria are prokaryote and are the most successful organisms on the planet
as they came about two billion years before the first eukaryotes. There are three main types: bacilli
(rod-shaped), Cocci (sphere-shaped) and Spirilli (spiral-shaped). Like eukaryotes, bacteria contain a
cytoplasm, a plasma/ cell membrane (a barrier to the cell), ribosomes and DNA, which is a large
circular strand, located in the nucleoid, a region in the cytoplasm of the cell. Unique features of
bacteria cells include: a cell wall, which consists of peptidoglycan; a molecule of sugars and amino
acids, its function is to protect the bacteria. Bacteria cells also have a flagella, a tail- like feature
which helps bacteria to move. They are often associated as a tiny whip, pushing the bacteria forward
(CK-Foundation 2019).
How to tell if an organism is a bacteria: Bacteria are singular- celled and membrane- lacked
organisms, with a simpler cell structure compared to other organisms.(Microbiology Society 2019)
They have no nucleus; instead some have an extra circle of genetic material called a plasmid, which
makes these organisms easy to identify. Their genome is a single loop of DNA. Bacteria cells are
surrounded by a cell wall, used for strength and rigidity (Lumen- Boundless Microbiology 2019).
How they affect other organisms: For infecting organisms to survive, they leave an existing
reservoir in current host, or another place. From direct contact, when an individual comes in contact
with a reservoir (population of organisms or the specific environment) by touching infected body fluid,
or being bit by an a animal/ insect carrying the bacteria ( a vector). Sexual contact is the leading factor
which causes bacterial infection caused by direct contact. Whereas by indirect contact, an individual
comes in contact with certain types of bacteria that survive inside the host. Infection is likely to occur
when they exist on personal care products such as toys, doorknobs, etc.
Lifecycle: The lifecycle of a bacteria consists of four stages: lag phase, log/ exponential phrase,
stationary phrase and death phase. In the lag phase, they adjust to their environment and metabolize.
They also begin making copies of their DNA, ready for the log phrase. The lag phrase is really short if the
environment already provides nutrients. During the log phase, bacteria cells rapidly multiply, the time it
takes for a culture to double is called generation time. In the stationary phase, bacteria growth
, decreases, due to accelerating waste, if any bacteria cells go to another culture, rapid growth can
continue. During the last stage (death), Bacteria cannot growth any further or reproduce; bacteria death
can be as rapid as their growth.
How it causes disease: Bacteria and viruses have similar ways in causing disease, however bacteria
has also other strategies. Firstly, they can multiply rapidly and in result, they outnumber the host tissues
and disrupt normal function of the body. They can also, straight forwardly, kill cells and tissues. Their last
strategy is to make toxins that paralyse and destroy cells’ metabolic machinery, or put forward a huge
toxic immune reaction (The National Academies of Sciences 2019).
What diseases it causes: Common diseases caused by bacteria include; pneumonia, meningitis and
food poisoning. Examples of bacterial skin infections include: cellulitis (causes painful, red infection),
folliculitis (infection of hair follicles), impetigo (common in young children; causes oozing sores) and boils
(deep skin infection that starts in the hair follicles)- On Health (2019)
How Meningitis damages the host: Meningitis is a bacterial disease, which causes the protective
membranes of the nervous system to swell. The inflammation of the brain and spinal cord can affect
every part of the body. Swelling of the brain can cause damage to the senses such as; hearing loss,
tinnitus- ringing of the ear, light sensitivity and eye pain. Loss of sight is also possible. Meningitis can also
affect the circulatory system; as bacteria multiply, they release toxins, which causes septicemia –
bleeding under the skin, which can cause blood vessel damage. (Healthline 2019)
Virus:
The main features: Viruses are tiny, non- cellular organisms that range from 30-50 nanometre. They
aren’t classified as living or non-living in biological terms as they don’t have enough characteristics to be
classified as living, but not too little to be classed as non-living. They don’t contain a cell wall, but instead
a protective protein coating called a capsid. They contain RNA/ DNA as their genetic material and can
only replicate inside a living cell (Byju’s 2019)
How to tell if an organism is one: Unlike other organisms, viruses cannot reproduce by
themselves; they have to infect a host cell. Also, they contain a protective protein coat called a capsule.
Viruses affect both eukaryotes and prokaryotes (ScienceDaily 2019).
How viruses infect other organisms: Viruses can only replicate themselves in living host cells.
They do this by injecting their DNA into the organism and then using the machinery of the host cell to
copy their DNA instead (Class Zone 2019)
Lifecycle: There are two difference types of lifecycles a virus can have: either a lystic cycle, or a
lysogenic cycle. Viruses have a lystic cycle if they have a prokaryotic host; e.g. bacteria. There are five
stages. The first is penetration: the virus enters the host cell. Secondly, is biosynthesis, where the phage
DNA replicates and where phage proteins are made. Then, the new phage particles are assembled; this is
maturation. Lastly, the cell lyses releasing newly made phages. In the lysogenic cycle, the phage genome
also enters the cell through attachment and penetration. The phage infects the cell, the phage DNA
becomes incorporated into the host’s genome. Then, the cell divides and prophage DNA is passed onto
the daughter cells. With stressful conditions, prophage DNA is excised from the bacterial chromosome
and enters the lystic cycle ( Lumen Learning 2019)
How it causes disease: Viruses cause disease using the following five stages: attachment, infection,
production, assembly and release. In the first stage, they attach themselves to the surface of the
organism, then the virus injects its DNA into the organism. In production, using the machinery used by
the host for copying its DNA, it instead copies the viruses DNA. In the fourth stage, new viruses assemble
In this assignment I will discuss infectious diseases and non-infectious diseases. Infectious diseases
are caused by five main pathogens such as: bacteria, virus, fungi, protozoa and parasite. Whereas,
non-infectious diseases are caused by a number factors such as: diet, environment, genetics and
degeneration. Then I will write a case study about an example of an infectious disease, stating the
symptoms and how the pathogens cause the disease to progress over time and the affect it has on
organs in the body and body systems. Similarly, I will write a case study about a non- infectious
disease and how I will analyse the effects of it on the human body. An infectious disease is a
disorder caused by pathogens that live in our body, normally completely harmless (Mayo Clinic
2019). However, under a change of conditions, some can cause disease; a disease which can be
passed by contact. A non- infectious disease is a disease which cannot be spread with any contact
from neither a human nor an animal, so they aren’t caused by pathogens or cannot be spread by a
vector (Study.com 2019)
Bacteria:
The main features: Bacteria are prokaryote and are the most successful organisms on the planet
as they came about two billion years before the first eukaryotes. There are three main types: bacilli
(rod-shaped), Cocci (sphere-shaped) and Spirilli (spiral-shaped). Like eukaryotes, bacteria contain a
cytoplasm, a plasma/ cell membrane (a barrier to the cell), ribosomes and DNA, which is a large
circular strand, located in the nucleoid, a region in the cytoplasm of the cell. Unique features of
bacteria cells include: a cell wall, which consists of peptidoglycan; a molecule of sugars and amino
acids, its function is to protect the bacteria. Bacteria cells also have a flagella, a tail- like feature
which helps bacteria to move. They are often associated as a tiny whip, pushing the bacteria forward
(CK-Foundation 2019).
How to tell if an organism is a bacteria: Bacteria are singular- celled and membrane- lacked
organisms, with a simpler cell structure compared to other organisms.(Microbiology Society 2019)
They have no nucleus; instead some have an extra circle of genetic material called a plasmid, which
makes these organisms easy to identify. Their genome is a single loop of DNA. Bacteria cells are
surrounded by a cell wall, used for strength and rigidity (Lumen- Boundless Microbiology 2019).
How they affect other organisms: For infecting organisms to survive, they leave an existing
reservoir in current host, or another place. From direct contact, when an individual comes in contact
with a reservoir (population of organisms or the specific environment) by touching infected body fluid,
or being bit by an a animal/ insect carrying the bacteria ( a vector). Sexual contact is the leading factor
which causes bacterial infection caused by direct contact. Whereas by indirect contact, an individual
comes in contact with certain types of bacteria that survive inside the host. Infection is likely to occur
when they exist on personal care products such as toys, doorknobs, etc.
Lifecycle: The lifecycle of a bacteria consists of four stages: lag phase, log/ exponential phrase,
stationary phrase and death phase. In the lag phase, they adjust to their environment and metabolize.
They also begin making copies of their DNA, ready for the log phrase. The lag phrase is really short if the
environment already provides nutrients. During the log phase, bacteria cells rapidly multiply, the time it
takes for a culture to double is called generation time. In the stationary phase, bacteria growth
, decreases, due to accelerating waste, if any bacteria cells go to another culture, rapid growth can
continue. During the last stage (death), Bacteria cannot growth any further or reproduce; bacteria death
can be as rapid as their growth.
How it causes disease: Bacteria and viruses have similar ways in causing disease, however bacteria
has also other strategies. Firstly, they can multiply rapidly and in result, they outnumber the host tissues
and disrupt normal function of the body. They can also, straight forwardly, kill cells and tissues. Their last
strategy is to make toxins that paralyse and destroy cells’ metabolic machinery, or put forward a huge
toxic immune reaction (The National Academies of Sciences 2019).
What diseases it causes: Common diseases caused by bacteria include; pneumonia, meningitis and
food poisoning. Examples of bacterial skin infections include: cellulitis (causes painful, red infection),
folliculitis (infection of hair follicles), impetigo (common in young children; causes oozing sores) and boils
(deep skin infection that starts in the hair follicles)- On Health (2019)
How Meningitis damages the host: Meningitis is a bacterial disease, which causes the protective
membranes of the nervous system to swell. The inflammation of the brain and spinal cord can affect
every part of the body. Swelling of the brain can cause damage to the senses such as; hearing loss,
tinnitus- ringing of the ear, light sensitivity and eye pain. Loss of sight is also possible. Meningitis can also
affect the circulatory system; as bacteria multiply, they release toxins, which causes septicemia –
bleeding under the skin, which can cause blood vessel damage. (Healthline 2019)
Virus:
The main features: Viruses are tiny, non- cellular organisms that range from 30-50 nanometre. They
aren’t classified as living or non-living in biological terms as they don’t have enough characteristics to be
classified as living, but not too little to be classed as non-living. They don’t contain a cell wall, but instead
a protective protein coating called a capsid. They contain RNA/ DNA as their genetic material and can
only replicate inside a living cell (Byju’s 2019)
How to tell if an organism is one: Unlike other organisms, viruses cannot reproduce by
themselves; they have to infect a host cell. Also, they contain a protective protein coat called a capsule.
Viruses affect both eukaryotes and prokaryotes (ScienceDaily 2019).
How viruses infect other organisms: Viruses can only replicate themselves in living host cells.
They do this by injecting their DNA into the organism and then using the machinery of the host cell to
copy their DNA instead (Class Zone 2019)
Lifecycle: There are two difference types of lifecycles a virus can have: either a lystic cycle, or a
lysogenic cycle. Viruses have a lystic cycle if they have a prokaryotic host; e.g. bacteria. There are five
stages. The first is penetration: the virus enters the host cell. Secondly, is biosynthesis, where the phage
DNA replicates and where phage proteins are made. Then, the new phage particles are assembled; this is
maturation. Lastly, the cell lyses releasing newly made phages. In the lysogenic cycle, the phage genome
also enters the cell through attachment and penetration. The phage infects the cell, the phage DNA
becomes incorporated into the host’s genome. Then, the cell divides and prophage DNA is passed onto
the daughter cells. With stressful conditions, prophage DNA is excised from the bacterial chromosome
and enters the lystic cycle ( Lumen Learning 2019)
How it causes disease: Viruses cause disease using the following five stages: attachment, infection,
production, assembly and release. In the first stage, they attach themselves to the surface of the
organism, then the virus injects its DNA into the organism. In production, using the machinery used by
the host for copying its DNA, it instead copies the viruses DNA. In the fourth stage, new viruses assemble
