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White blood cells
· Also known as leucocytes
· Defend body against pathogens
· Pathogens are disease causing organisms
· Made in bone marrow by division of stem cells
· Neutrophils are lobed and largest of leucocytes role is
phagocytosis
· Lymphocytes are small with a large, round nucleus
· B-lymphocytes produce antibodies (humoral response)
· T-lymphocytes are involved with the cell-mediated response
· Monocytes are large with a kidney shaped nucleus develop into
macrophages
· Eosinophils are associated with allergies
· Basophils release chemicals such as histamines that cause
inflamation…read more

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Types of bacteria
· Coccus spherical
· Spirillum spiral shape
· Bacillus rod shaped
· Gram positive retains crystal violet dye because
crystal violet is trapped in the peptidoglycan wall
· Gram negative retains saffronin because
lipopolysaccharide layer that prevents crystal violet
being trapped in the peptidoglycan wall is made more
permeable by the crystal violet dye, so that the
counter stain saffronin can be taken up by the
peptidoglycan wall…read more

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Bacterial growth
· Lag phase is when the pathogen is active but there is
little growth as they are taking up water and producing
enzymes
· Exponential/log phase is where the population size
increases rapidly
· Carrying capacity is when the maximum population the
environment can support is reached
· Stationary phase is when the pathogens are dying at
the same rate as they are produced
· Death phase is when pathogens are dying faster than
they are being produced due to lack of nutrients, lack
of oxygen or accumulation of toxic waste products…read more

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Factors affecting growth
· Temperature
­ Thermophiles have optimum temperature of above 40 degrees grow in hot springs,
compost heaps and water heaters
­ Mesophiles have optimum temperature between 20 and 40 degrees most bacteria
including human pathogens
­ Cryophiles have optimum temperature below 20 degrees live in Arctic and Antarctic
Oceans, fridges and freezers
· pH
­ Most have optimum of pH 7 and cannot function below pH 4
­ Bacteria produce waste products with low pH and can lead to death of bacteria population
· Oxygen
­ Needed for aerobic bacteria to produce ATP
­ Obligate anaerobes are killed if oxygen is present
· Nutrients
­ Essential for growth
­ Nitrogen needed for protein synthesis…read more

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Culturing bacteria aseptic
technique
· Cuts covered with clean, waterproof dressing
· No food or drink in lab
· Windows and doors closed to avoid airborne contamination
· Wash hands with anti-bacterial soap before and after
· Wipe down bench with disinfectant before and after
· Tape petri dish securely after inoculation and label them
· Keep temperature below 30 degrees
· Sterilise all containers using autoclave (121 degrees for 15 mins) before
and after to destroy spores
· Sterilise equipment throughout innoculation by placing in alcohol then
burning off alcohol with bunsen flame
· Work near lit bunsen burner to produce convection currents to kill
airborne infections
· Lift petri dish lid at 45 degree angle
· Do not open petri dishes after inoculation…read more

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