Chapter 10- Diseases Of Plants And Animals Flashcards
What is a parasite
These live inside or on the surface of another organism known as the host. They obtain their energy and nutrients from the host, as well as protection.
What are microorganisms that cause disease called
Pathogen
What type of diseases do pathogens cause
Communicable diseases- infectious diseases
The diseases that are not caused by pathogens are non-communicable diseases (e.x genetic diseases and deficiency diseases caused by poor diet
How does disease transmission occur
The transfer of pathogens from an infected host to an uninfected host.
Why is it important to know how pathogens are transferred between cells
By knowing this, we can devise suitable control methods to stop them spreading.
This often involves public expenditure o improve the infrastructure of a country, as with diseases spread through water contaminated by human gut pathogens (e.g cholera and typhoid). In other cases, people have to take precautions such as sleeping under bed nets to avoid malaria and adopt a good hygiene to prevent the spread of airborne pathogens and those transferred by direct contact.
What are the four type of pathogens
Bacteria
Viruses
Fungi
Protoctists
Whata are bacteria
These are prokaryotic organisms with a huge diversity of different types. For example, there are bacteria that cause tuberculosis (Mycobacterium tuberculosis) and also the bacteria that causes meningitis ( one of these are Neisseria meningitis)
Both of these bacteria are intracellular parasites- they infect human cells
How does meningitis occur
The meninges are the tissues that surround the brain and the spinal cord. They prevent the entry of most bacteria but N.meningitis is one of the few that can pass through the barrier to cause the disease, meningitis.
Some viruses also cross the meninges to cause a viral form of the same disease.
What are some bacterial pathogens for plants
Bacterial pathogens of plants tend to kill their host and then feed off their dead and decaying tissues. Thus, these pathogens cause the most damage to the crops compared to viral or fungal diseases.
Many bacterial diseases of plants are called rots. E.g when you peel a potato and the inside and outside go black.
The bacteria that cause ring rot in potatoes infect vascular tissue (xylem and phloem) and block it so that less water reaches the leaves and they wilt. The disease first spreads through the vascular tissue in the stem and into the developing tubers. Vascular tissue in tubers is arranged as a ring.
What are viruses
Tobacco mosaic virus (TMV) was the first virus to be discovered. Many other viruses cause mosaic diseases, which have the symptom of a yellowing of the leaves to give a mosaic pattern. TMV is a much simpler virus- it has a rod of protein surrounding a coil of single-stranded RNA.
The RNA is the genetic material of the virus and codes for four proteins.
How are influenza (A, B and C) viruses like
These hijack the host cell’s metabolism to make more of themselves. These are parasites and have no cellular structure, so they cannot respire, make ATP or transcribe and translate the genes coded by the genetic material. Once a virus infects a cell, it hijacks the cell’s machinery to make more copies of its genetic material and the proteins needed to make the coat, or capsid.
The most influenza is influenza A which is responsible for worldwide epidemics. Influenza A has a capsid that surrounds eight single-stranded molecules of RNA that between them code for 11 genes. This virus infects the cells lining the airways of the gas exchange system.
How does a virus transferred between cells
As virus particles leave their host cells they are enveloped in a phospholipid bilayer derived from the cell surface membrane. This membrane contains two types of glycoprotein- haemagglutinin and neuraminidase- which are involved in infecting new host cells and are coded by the genes in the viral RNA. The HIV (human immunodeficiency virus) infects cell types, including brain cells and some in the immune system. Like influenza, it is an enveloped virus with RNA as its genetic material. The protein capsid of the virus is surrounded by a matrix of viral protein and then a phospholipid bilayer that is formed from the cell surface membrane of its host cell from which it emerged. Molecules of glycoprotein can be inserted into the molecules of cell surface proteins which allows the virus to these.
What is a retrovirus
A virus, such as HIV, with single-stranded RNA as its genetic material, not DNA. When a retrovirus invades a host cell, it uses its enzyme reverse transcriptase to make DNA from an RNA template. Other viruses such as Influenza, do not use their RNA to form DNA
What enzymes are involved in retrovirus activity
Enzyme reverse transcriptase converts the RNA to a single-stranded DNA.
Then DNA polymerase replicates the DNA to form a double-stranded helix
The DNA enters the nucleus, where the enzyme integrase attaches it to host DNA.
What will the viral DNA that is integrated to the DNA of the host cell do
It remains inactive for several years; it is a provirus
