Unit number and title: Unit 12 Diseases and Infection
Learning Aim A: Investigate different types of diseases and infections that can affect humans
Title: Infectious & non-infectious diseases
RED= RESUBMISSION
A.P1
Lysogenic and lytic cycle:
Viruses undergo two types of DNA replications which are known as the lysogenic and lytic cycles. The
Lysogenic cycle is when a virus reproduces its DNA by using a host cell and can be triggered by many
factors like environmental factors. The DNA is only replicated but not changed into proteins unlike
the lytic cycle where the DNA is multiplied numerous times and the proteins are formed by utilising
processes stolen from bacteria. They inject their genetic material but instead, the genetic material
stays hidden in the host DNA. The stages involved in the lysogenic cycles are:
1. A special virus called bacteriophage which means a virus that goes after bacteria infects a
bacterium by injecting its DNA into the bacterial cytoplasm.
2. The same bacterial proteins that replicate bacterial DNA read and reproduce the viral DNA
3. If the viral DNA remains in the lysogenic cycle, then one or more copies of the DNA exist in
many bacteria and the DNA will only reproduce when the bacteria replicate its individual
DNA
4. Ultimately, the viral DNA changes to the lytic cycle where bacterial mechanisms are involved
in the production of many capsids and DNA.
5. The capsids are then freed into the atmosphere where it infects new bacteria, and this is
how the lysogenic cycle happens again. However, the virus would enter the lytic cycle if the
bacteria were dying or weak so that it averts dying with the bacteria.
The lytic cycle is a process of viral reproduction where DNA is replicated, and capsid cases are
produced to transport it. The lytic cycle is also when the virus attaches to a host cell and injects its
RNA or DNA depending on the material kind and it makes lots of viruses and causes the cell
membrane of the host to rupture. The stages involved in the lytic cycles are:
1. Adsorption and penetration= In this process the bacteria receive their RNA or DNA into the
host cell. The viral genome has a coat of protein around it. This protein coat protects the
viral genes, and it also unlocks a cell. The shape of the protein surface enables them to
engage with proteins on the surface of the host cell. When the cell and the shields of protein
are in alignment, the virus attaches itself to the cell membrane which causes the shape of
the capsid to alter. When this occurs, a hole is torn, or the viral DNA is injected into the cell
host. Depending on the type and conditions of the genome and cell, the virus might
reproduce in the cytoplasm or might make its way to the nucleus.
2. Replication= When the lytic cycle takes place, the reproduction of viral genes is repeated
many times by the cellular system that is controlled by the virus. The proteins produced
initially are frequently made as the cell replicates its own DNA and creates proteins where
the viral genes join the process thus making the viral early proteins. The early protein is
extremely vital in the function of the virus hijacking the cells works as they clear the cell’s
normal metabolic programme and transform various of its undertakings to the production of
viral proteins and the reproduction of the viral genes. The virus then utilises the new
1
, products that the cell gathered such as the nucleic and amino acids in order to replicate
itself.
3. Assembly and Release= Although the other viral life cycles do not involve the production and
gathering of new virions, the lytic cycle does. Each part of the virus is made individually,
assembled, and then dispatched into the atmosphere and environment.
Lifecycle of Plasmodium (Malaria):
Plasmodium undertakes several stages of development in the mosquito’s body. The mosquito bites
the human being by injecting saliva which holds plasmodium sporozoites. The sporozoites infect the
liver cells which then burst hence releasing plasmodium cells that infect the red blood cells. The
infected red blood cells burst and when this occurs, plasmodium cells are released, some infect
other red blood cells whilst the others may infect the mosquitoes. Anopheles mosquito bites the
infected human being and picks up the plasmodium cells. This is known as the lifecycle of
plasmodium.
A.P2
5 Main types of pathogens= examples of diseases
Pathogen Disease Effect Symptoms
Virus HIV Loss of body weight Cold, tuberculosis
Bacteria Cholera Rapid loss of bodily Leg cramps, vomiting,
fluids leads to watery diarrhoea
dehydration
Parasites Toxoplasmosis Can lead to seizures Swollen lymph glands,
and life threatening fever, headache,
muscle ache
Fungus Candidiasis Can cause skin to Thrush on skin,
become darker due to armpits, groin and
rash between the fingers
Protozoa Malaria Loss of body weight, Fever, nausea,
severe anaemia vomiting, fatigue and
headaches
Disease Pathogen Characteristics
Tuberculosis Bacteria Small, rod shaped, very
aerobic and acid-fast bacillus
Meningitis Bacteria, fungi or viruses Inflammation of the
membrane around the brain or
spinal cord
HIV / Aids Virus It will remove or destroy
immune system
Influenza RNA Viruses Single stranded of an RNA
virus enclosed in a helical
nucleocapsid
Malaria Plasmodium Malaria has hot or cold or even
wet phases, this will happen
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