Lab test Flashcards
How should liquid from an auto-pipette be drawn?
It should be drawn and dispensed slowly.
Why should an auto-pipette be drawn slowly?
To ensure the correct volume is drawn & dispensed.
True/false: Immersion oil should contact the objective lens of a microscope
True.
Why should an agar plate be labelled on the base?
- Face down
- Condensation doesn’t ruin the inoculated plate
- Scientists can identify who it belongs to without damaging the colony
Why should a glass spreader dipped in ethanol NOT immediately be used to spread cells?
The ethanol will kill or damage the bacterial colony.
Equation: Solve to find C1
C1=C2xV2/V1
Equation: Solve to find C2
C2=C1xV1/V2
Equation: Solve to find V1
V1=C2xV2/C1
Equation: Solve to find V2
V2=C1xV1/C2
Equation: Solve to find the diluent
Diluent= V2-V1
What is Beer’s Law?
The linear relationship between absorbance and concentration. It is linear only over a certain range of concentrations.
What if the absorbance reading of an unknown solution is higher than any of the absorbances in the linear range?
You cannot assume that Beer’s law is still obeyed so you cannot extrapolate beyond the linear portion of a standard curve.
What happens if Beer’s Law is not obeyed?
You must dilute the unknown solution so that its absorbance falls within the linear portion of the curve.
How do you calculate the amount of protein per assay (P)?
Volume x Concentration of the albumin solution.
Explain how to measure the standard curve to find the amount of protein in an unknown solution
- Volume x concentration of solution
- Put it on the Y axis
- Rule to the line of best fit
- Rule down to the X axis
What treatments do you use when Gram staining cells?
crystal violet & iodine then a decolourizing agent followed by safranin.
What colour do Gram-negative (Gm-) organisms stain?
pink or red.
What colour do Gram-positive (Gm+) organisms stain?
purple or violet
What are the cell walls of Gram-negative organisms rich in?
lipid.
What does the decolourizing agent do to the lipid of the cell walls of an organism?
Removes the cell wall lipids & decolourizes the cell contents. Safranin then stains them pink or red.
What do Gram-positive cells have?
a thick peptidoglycan layer.
What does the decolourizing agent do to the peptidoglycan layer?
the pores shrink and form a barrier, trapping the crystal violet/iodine complex inside the cell.
Lag phase
Directly after inoculation there’s a period of little to no growth
Log phase
A period in during which the cell density doubles in some constant time interval
