Infection and Immune System Flashcards
How HIV particles enter T helper cells
- HIV particles have GP120 on surface of its virus
-T helper cells have CD4 receptors that the GP120 bind to - Viral envelope fuses with cell membrane of T helper cell
- Viral RNA enters cell
Why does the destruction of T helper cells cause the symptoms of AIDS?
- Lack of T helper cells means less cytokines are produced
- This means that the cloning of B cells is also reduced
- Therefore the production of antibodies are reduces
- Thus an increased risk of opportunistic infections
Which cells produces antibodies?
Plasma cells
Explain why the presence of microorganisms on the skin and in the gut helps to prevent pathogenic organisms multiplying in the body.
- Gut flora and skin flora are better adapted to these conditions
- Therefore can outcompete pathogenic organisms
- Bacteria in the gut will secrete chemicals/ lactic acid that help destroy pathogens.
The human immunodeficiency virus (HIV), causes acquired immunodeficiency syndrome (AIDS).
A small number of people have been identified who are resistant to HIV. They have a mutation in a gene coding for a protein in the cell membrane.
(i) Deduce why this mutation makes these people resistant to HIV infection.
- Protein is a receptor in the cell surface membrane of T helper cells
- GP120 cannot bind to the CD4 receptor
- Therefore Viral RNA cannot enter the cell.
Stem cell therapy can be used to treat patients infected with HIV.
The bone marrow of these patients can be destroyed using radiotherapy.
The patients can then be given stem cells from the bone marrow of a donor who has this mutation.
Explain why these stem cells may prevent HIV causing AIDS.
- Stem cells in the bone marrow can differentiate into specialised cells
- These cells can differentiate into T helper cells that are resistant to HIV
- T helper cells are destroyed by HIV so a patient cannot produce an immune response
- mutated CD4 receptor prevents HIV entering the raplacement T helper cells
- T helper cells are not destroyed therefore AIDS don’t develop/HIV not in the blood.
Penicillin is an antibiotic. It was discovered in 1928. Since then many antibiotics have been identified and are widely used in the treatment of bacterial infections.
Scientists have recently discovered a new class of antibiotics that bind to ribosomes. (i) Explain why these antibiotics could affect the production of proteins in bacteria.
- Proteins cannot be synthesised
- Because the ribosome shape is altered
- Meaning that the mRNA cannot bind to the ribosome
- Therefore translation can’t go on
(ii) These new antibiotics attach to a site on the ribosome not affected by any known antibiotics.
Deduce why these new antibiotics might be used to treat bacteria that are resistant to other antibiotics.
- The bacteria hasn’t been exposed to the new antibiotics before
- Bacteria have developed resistance to other antibiotics by natural selection/ evolving
- therefore there has been no mutation to give resistance to the new antibiotics.
- (iii) Scientists have isolated these new antibiotics and tested their effectiveness against
bacteria that are resistant to other types of antibiotic.
Devise a laboratory procedure to compare the effectiveness of penicillin with one of the new antibiotics.
Human papilloma virus (HPV) is a DNA virus.
Cervarix and Guardasil have been used in national vaccination programs.
A person who has been vaccinated becomes infected with HPV-16. Explain the role of the T cells in the body of this person.
- A vaccinated person will have memory T cells
- Memory T cells recognise antigens specific to the HPV-16 Virus
- T helper cells activate B cells/T killer cells
- Formation of T killer cells destroys cells infected with virus
The human gut contains more than a thousand species of bacteria. Only 30 to 40 of these species are found in the stomach.
Explain why there are relatively few species of bacteria in the stomach.
pH of the stomach is too low for the enzyme activity of bacteria to function
Bacteria that live in the stomach are adapted to withstand these conditions.
Bacteriostatic antibiotic definition
Bacteriostatic antibiotics inhibit the growth of bacteria through stopping protein synthesis and production of nucleic acids so bacteria cant divide and grow.
Bactericidal antibiotic definition
They kill bacteria by destroying their cell wall and thus causing them to burst (lysis)
Compare and contrast the structure of Ebola virus with that of the human immunodeficiency virus (HIV).
Similarities:
- Both contain RNA
- Both have glycoprotein/protein capsid
Differences:
- Ebola contains one strands of RNA
- HIV contains two strands of RNA
-HIV is spherical
-Ebola is elongated
A newborn baby can respond to infections.
Interferon is involved in the response to viral infections.
(i) The influenza virus can be lethal to mice.
The effects of interferon on influenza infection in mice was investigated. Mice were infected with influenza virus and then given an increasing dose of interferon. What impact does this have?
Increasing dose of interferon increases the survival time of the mouse because interferon inhibits viral replication inside cells
The greater the dose, the fewer the virus particles released to infect other cells
