Biology- Unit 6 Flashcards
What is the lag phase?
Microorganisms are adjusting to the environment before starting to reproduce
What is the log phase?
Population size grows exponentially, every round of division doubles population size
What is the stationary phase?
When population reaches maximum due to decreasing nutrient levels and build up of toxic substances
What is the death phase?
Lack of nutrients and toxic products causes death of organisms
How would a cell count be carried out?
Haemocytometer
Sample of broth is diluted 1:1 with trypan blue (stains dead cells blue)
Counted cells have to be fully in boxes
Useful because it only counts living cells and is accurate- but slow an expensive
How would turbidimetry be carried out?
Form of colorimetry
As turbidity increases, absorbance increases
Counts dead cells, expensive, assumes density of cells is constant
How would dilution plating be carried out?
Colony is grown from a single, viable microorganism
Original culture is serially diluted and streak plating to count individual colonies.
Slow due to incubation period
What are endotoxins and which bacteria secrete them?
Lipopolysaccharides in the outer membrane - gram negative
Salmonella
What are exotoxins and which bacteria secrete them?
Soluble proteins produced and released by bacteria as they metabolise and reproduce
Staphylococcus
What is an example of bacterial disease caused by host tissue invasion?
Tuberculosis
1) First infection is symptomless, infected phagocytes are sealed in tubercles as a result of the inflammatory response
2) Bacteria lie dormant in tubercles and are not destroyed by immune system
3) When immune system weakens, bacteria become active again and destroy lung tissue
What is a bactericidal antibiotic?
Destroy bacteria’s cell wall and cause them to burst
What is a bacteriostatic antibiotic?
Inhibit growth of bacteria by stopping protein synthesis and production of nucleic acids
How can bacterial resistance be combatted?
1) New patients are screened at arrival and isolated if they are infected
2) Antibiotics are only used when needed and courses are completed to minimise selection pressure to prevent resistant strains
3) Strict hygiene, antibiotic gel hand wash, suitable clothing
Describe how influenza infects and effects the host
Droplet infection
Infects ciliated epithelial cells- injects viral RNA, host produces new viruses, lysis of cell
Headache, sore throat, coughing, vomiting, fever
Describe how stem rust infects and effects the host
Spores via wind/ infected fragments
Spore germinates in water- produces hyphae which enter the plant, grow into mycelium, digest plant and absorb nutrients
Weakened stem, water loss, reduced photosynthesis, pustules on epidermis burst to release more spores
Describe how malaria infects and effects the host
Female anopheles mosquito saliva
Parasite travels to liver, infect RBCs, reproduce asexually inside erythrocytes and cause lysis
Sweating, shaking, anaemia, muscle pains, headaches, liver damage
How can influenza be treated?
Anti-viral medication
Antibiotics
Painkillers
How can malaria be treated?
Mosquito nets Insect repellent Treating still water with pesticides Proper disposal of sewage Antimalarial drugs
What are the physical barriers to infection?
Skin- keratin
Stomach acid
Gut and skin flora- competitive
What are the non-specific responses to infection?
Inflammation- vasodilation, increase permeability of vessels, more antibodies, WBC
Fever- decreases speed of pathogen reproduction, increases rate of specific immune response
Phagocytosis- WBC engulf pathogens
Lysozyme action- found in tears and mucus, damages bacterial cell walls
Where do B cells mature?
Bone marrow
Where do T cells mature?
Thymus gland
Describe the cell mediated response
Pathogen invades host cell
1) Host cell resents antigen on MHC protein
2) T killer cell with complimentary receptor proteins binds to Antigen-presenting cell
3) Cytokines secreted by T helper cell stimulated T killer cell to divide by mitosis
4) T killer cell divides to form active T killer cells and T memory cells
5) Active T killer cells bind to APCs and secrete chemicals which cause pores to form in cell membrane
6) Infected cell dies
Describe the humoral response
1) Bacterium is engulfed by macrophage which presents antigen on MHC protein
2) Macrophage APC binds to complimentary T helper cell
3) The T helper cell is activated and divides by mitosis to form T memory cells and active T helper cells
4) T helper cell presents antigen on MHC protein and activates complimentary B cell with cytokines
5) Cytokines cause B cell to divide rapidly by mitosis to form plasma cells
6) Plasma cells secrete complimentary antibodies
What do antibodies do?
They render the pathogens harmless by binding to antigen and group pathogens together so they can be engulfed by macrophages faster
What is natural active immunity?
Exposed to antigen/ suffered the disease
What is natural passive immunity?
Crossing of a mother’s antibodies through placenta and breast milk
What is active artificial immunity?
Vaccinations
What is passive artificial immunity?
Injection of antibodies into body
