TOPIC 6: MICROBIOLOGY AND PATHOGENS Flashcards
Why would we use several nutrient agar plates
To improve reliability
Why would we include the same concentration of antibiotic
For validity
Is cytoplasm found in both bacteria and viruses
No- Only bacteria contain cytoplasm
Explain what is meant by the term bacteriostatic antibiotic
Bacteriostatic antibiotic is used to prevent the reproduction/division of bacteria and it is the immune system that will kill the bacteria
Explain what is meant by the term bactericidal
antibiotic
Bactericidal antibiotics destroy and kill the bacteria
Where are B and T cells formed
In the Bone marrow
How are B cells and T cells able to form clones
Via mitosis
State two ways in which the skin flora can help to protect a person from infection by pathogenic bacteria.
- Skin flora competes with pathogenic bacteria for space and nutrients
- Skin flora secretes chemicals that affect PH to prevent bacteria from growing
Which part of the skin forms a physical barrier against infection by pathogenic bacteria
Epidermis
Suggest why antibiotics may be used as part of the treatment for influenza.
- Influenza may allow development of other infections/diseases so antibiotics will kill/inhibit growth of bacteria
Explain why doctors have been advised to limit the prescription of antibiotics.
- To prevent bacteria from being resistant to the antibiotic as resistant bacteria can survive and pass on this useful gene and it would be harder to contain the infection
- Some infections cannot be treated with antibiotics
Describe how you could investigate the effect of different antibiotics on bacteria
- Distribute bacteria on the agar in the petri dish evenly using an inoculating loop
- Apply different antibiotics in the wells of the agar
- Control the antibiotic concentration
- Use aseptic technique and incubate at a suitable temperature
State one characteristic symptom of TB other than coughing.
Bloody sputum
What is the name of the organism that causes TB
Mycobacterium tuberculosis
Describe how the organisms that cause TB are taken up by macrophages.
- Bacterium are recognised as non self cells due to their antigen
- B lymphocytes detect bacteria and phagocytosis takes place engulfing the bacterium which is then broken down by enzymes in the lymphocytes vacuole
Give two differences between the genetic material of bacteria and viruses.
- Bacteria have DNA, Viruses however can contain RNA or DNA
- The bacteria have circular genetic material whereas viruses have linear genetic material
- Bacteria have plasmids whereas viruses do not
Suggest why treatment with antibiotics may not be effective against the
dormant bacteria in the tubercles.
- Bacteria in the tubercules contain a waxy layer which is harder for phagocytosis to occur.
- Bacteriostatic Antibiotics affect dividing bacteria not dormant ones
TB can be prevented by vaccination. Explain how a person can develop artificial active immunity following vaccination.
- Dead inactivated pathogen is put into the person which stimulates the primary immune response
- This activates T helper cells and B cells which then go on to produce memory cells
Explain why the activity of these bacteria (mycobacterium tubercolosis) and the inhibition of T cells means that
a person may quickly develop severe symptoms leading to death.
- The mycobacterium can cause lung damage which can cause severe breathing problems.
- The mycobacterium can also get into the blood which can lead to organ failure.
- The inhibition of T cells means that the immune system is now weakened which secondary infections may now cause death
Distinguish between the structure of bacteria and viruses
- Bacteria are cells, viruses are not.
- Bacteria are surrounded by cell wall/slime capusle, viruses however are surrounded by protein capsids
- The genome of Bacteria are DNA, Viruses can be DNA or RNA
Explain how antibodies help a person to recover from an infection.
- Antibodies bind to bacteria (opsonisation)
2. This causes phagocytosis to be greater
Explain what is meant by zone of inhibition
- Area where no bacteria are replicating
Explain why contamination of tissue cultures in investigations has to be avoided.
- The contaminants compete for nutrients and space
2. The contaminants can cause infection/ disease of tissue
Explain why the ambient temperature and the core temperature of the body are used to determine the time of death of a person.
- The temperature of the body changes with time after death.
- The core temperature depends on the ambient temperature
Describe the differences between a totipotent stem cell and a pluripotent stem cell.
- Totipotent stem cells can differentiate to become any cell
- Whereas pluripotent stem cells cannot differentiate to any cell
Describe how the bacteria should be added to the Petri dish.
- Aseptic technique/ use of sterile equipment
2. Spread bacteria on the agar evenly
Why is the petri dish sealed with tape
- To reduce contamination of culture.
2. Allow aerobic conditions to reduce growth of harmful bacteria
Suggest why an incubation temperature of 37°C should not be used in a
school or college laboratory.
encourages growth of bacteria that are harmful to humans
Suggest what is meant by the phrase suitably-prepared Petri dish.
- Contains agar
- Bacteria are distrubuted evenly
- Petri dish contains one single bacteria strain
Describe how a B cell is activated.
- Bacteria/virus/pathogen binds to B cell - the antigen of the pathogen binds to the MHC antigens
- T helper cells bind to B cells
- Referance to cytokines
Describe the role of antigen presentation in the body’s specific immune response
to infection by viruses.
- Macrophages present antigen on their MHC to T helper cells
- T helper cells bind to macrophages and are activated.
- B cells also act as APCs and produce plasma that differentiate into antibodies
- Infected host cells also present antigens to T killer cells which then go onto destroy infected host cells
Describe how infection with a bacterium results in the production of plasma
cells.
- Humoral immune response
- The macrophage engulfs the bacterium via phagocytosis and presets the bacteriums antigens on its surface the macrophage becomes an APC
- Macrophage APC binds to a T helper cell and activates it. Once the T helper cell is acrivated it divides to form memory T cells and active T helper cells.
- In the effector stage B cells become APC and present the bacteriums antigens on their MHC
- T helper cell complementary binds to the APC and produces cytokines that stimulate the B cell.
- B cells then form clones (B effector and B memory cells).
- The B effector cells differentiate into plasma cells
What type of cell in the human immune system is infected by HIV
T helper cells
What is the enzyme used to produce DNA from viral RNA in an infected cell
Reverse transcriptase
(i) State two characteristic features of antibodies.
- They are glycoproteins that have an antigen binding site
Explain why an insect bite, which breaks the surface of the skin, may lead to
inflammation around the injury.
- Histamine released as a result of damaged tissue and is released from platelets.
- The histamine causes vasodilation and an increased blood flow to the area causing redness and swelling
Where are B and T cells formed
In the Bone marrow
(i) Explain what is meant by the term genetic mutation.
- Change in the base in DNA
2. Which leads to change in the sequence of amino acids in the primary structure of the protein
What do white blood cells plant cells and prokaryotic cells all contain
- Ribosomes
What can Totipotent stem cells give rise to
Totipotent stem cells and differentiated cells
What can Pluripotent stem cells give rise to
Only differntiated cells
Suggest how a stem cell in the bone marrow can become a differentiated blood
cell.
- A chemical stimulates some genes to be active in the bone marrow stem cell.
- So only the active genes are transcribed and mRNA is made which makes the proteins that make the stem cell into a blood cell
