C11 - Diseases Flashcards
What’s a disease?
The malfunction of the body or mind, which adversely affects the health of the individual.
The pathogen must first enter and penetrate the host’s first line of defence of the body then colonise the tissues.
What’s a communicable disease?
One which can spread from one person to another.
What’s virulence?
The ability for a pathogen to cause disease.
What’s a pathogen?
A microorganism that can cause disease and must enter the host, colonise and reproduce.
What are the 3 main ways in which pathogens cause disease?
1 - By producing toxins which damage the cells and cause symptoms e.g. Rashes and fevers
2 - Secreting enzymes that allow the pathogens to spread through tissues. Some symptoms are allergic reactions to the enzyme e.g. The fungus causing athletes foot.
3 - Entering them and preventing tissue function e.g. Viral replication. Viruses inhibit normal DNA, RNA and protein synthesis of the cell and use the mechanism to produce new viral particles which can cause the cell to rupture and infect new cells.
How do bacteria reproduce?
By binary fission (NOT mitosis)
How do bacteria differ from viruses?
Bacteria are prokaryotic cells with cytoplasm, circular DNA, plasmids, pilli, flagella etc. and reproduce asexually.
Viruses are small organic particles with no proper cell structure. They have a strand of nucleic acids enclosed within a protein coat and may have an outer envelope from the host cell containing glycoproteins from the virus. They enter cells and infect the host’s metabolic rate.
What’s TB?
Caused by Mycobacterium Tuberculosis, it’s a widespread disease that affects the respiratory system.
It’s transmitted through inhalation of infected water droplets e.g. coughs and sneezes.
What’s the full name of TB?
Mycobacterium tuberculosis
Why is TB so virulent?
It is able to inhibit the action of lysosomes in phagocytic cells that engulf it where it can survive and multiply.
What’s secondary TB?
When TB develops and many phagocytic and other cells accumulate round the infected cells to form a tubercle.
Lung tissue is damaged, sputum is bloodstained and it can be fatal.
How is TB treated?
By intensive care and extensive antibiotics over 6 months.
Why is TB so hard to cure?
It can develop resistance to antibiotics.
Multi-drug resistant TB (MDR TB) describes a strain resistant to 2 antibiotics.
Extensively drug resistant TB (XDR TB) describes a strain resistant to 3+ antibiotics.
What’s HIV/AIDS?
An immunodeficiency disease caused by a human immunodeficiency virus.
It’s a retrovirus, meaning it’s genetic information is in the from of RNA not DNA.
It enters and infects T helper cells.
How does HIV form?
It’s a retrovirus, meaning it’s genetic information is in the from of RNA not DNA.
It also has the enzyme ‘reverse transcriptase’ which will create the double stranded DNA copy of the viral genome once within the host T helper cell.
The viral DNA copy then becomes part of the DNA of the host cell, forming a provirus.
Once the viral DNA becomes active, viral RNA and proteins are synthesised by the cell and more viruses are produced while T helper cells are destroyed. This prevents resistance from the immune system. (Opportunistic infection)
How is HIV controlled?
There’s no cure.
Safe sex encouraged Reduced needle sharing encouraged Blood screening before transfusions Discourage infected mothers from breast feeding Test 'at risk' groups
What type of cell is HIV?
An acellular particle. They’re considered to be specialised parasites.
- It’s can’t reproduce alone, can’t grow and can’t divide
- They don’t transform energy
- They can’t synthesise proteins
What’s the structure of a virus?
They have a central core of genetic material, either DNA or RNA, surrounded by a capsid (protein coat).
The capsid is made up of proteins called capsomeres which may be surrounded by a lipid and protein membrane.
What is the structure of a HIV virus?
They are spherical and have a central core of two strands of genetic material (RNA) and the enzyme ‘reverse transcriptase’.
The RNA and reverse transcriptase is then surrounded by a capsid (protein coat) which is then surrounded by a spherical lipid and protein membrane.
What does reverse transcriptase (found in HIV) do?
It creates the double stranded DNA copy of the viral genome.
What’s a capsid?
The protein coat surrounding the genetic material in viruses.
The capsid is cone shaped and surrounded by a lipid and glycoprotein membrane, forming an envelope.
The glycoproteins form peg-like structures which bind to receptors on the cell surface membrane of T helper lymphocytes.
Why are aseptic techniques used to culture bacteria?
To prevent contamination.
E.g. Use sterile containers, add sterile agar jelly, inoculate the medium and clean surfaces.
What is gram stain?
A stain used for a method of bacteria staining containing the chemical ‘crystal violet’.
This splits bacteria into 2 groups, gram positive bacteria and gram negative bacteria.
How is a gram positive bacteria identified?
The crystal violet from the gram stain will stain the bacteria purple/blue which can be seen under a microscope.
