1.1 lab techniques for biologists Flashcards
what do risk assessments involve?
identifying hazards and implementing control measures to minimise the risk
what can control measures include?
handling techniques
PPE
aseptic techniques
what is the use of a burette?
to dispense precise volumes of liquid reagents
what is dilation?
reducing the concentration of a substance in a solution
what is serial dilution?
repeated dilution from a stock solution
how do linear dilutions work?
Dilutions differ by an equal interval
how do logarithmic dilutions work?
Dilutions differ by a
constant proportion
what is a colorimeter used for?
to determine the concentration of a pigmented compound
how does a colorimeter work?
it passes a light beam at a specific wavelength through a cuvette containing the sample solution
it measures the absorbance of this wavelength by the solution
how does a standard curve work to determine unknown concentrations?
a series of standards of known concentrations are measured and graphed
this graph is used to determine the concentration of an unknown sample
what is a pH buffer solution?
a solution whose pH changes very little when a small quantity of acid or base is added to it
how do buffers work?
they allow the addition of hydrogen/hydroxide ions without affecting the pH of the solution
according to which factors can substances be separated?
according to their
solubility
size
shape
charge
how does centrifugation separate substances?
according to their size
how do the largest and densest substances behave in a centrifuge?
they separate first and form a pellet at the bottom of the centrifuge
what is the name given to the liquid remaining at the top of the centrifuge?
the supernatant
describe proteins at their iso-electric point (a specific pH)
overall neutral charge and precipitate out of solution
describe the charges of proteins above and below their isoelectric point
positive charge at pH below their IEP
negative charge at pH above their IEP
what happens during isoelectric focussing?
a solution is buffered to a specific pH and only proteins with that IEP will precipitate
how does electrophoresis separate molecules?
based on their charge, size and shape
how does protein electrophoresis work?
current flows through a buffer
the gel acts as a sieve, separating the proteins
which factors does SDS-PAGE separate proteins based upon?
size only - proteins are denatured and given a uniform charge