lab techniques Flashcards
define risk
the likelihood of harm arising from exposure to a hazard
what are the types of hazard?
toxic or corrosive chemicals, heat or flammable substance, pathogenic organisms and mechanical equipment
what control measures are used to control risk
appropriate handling techniques,protective clothing and equipment and aseptic techniques
What does risk assessment involve?
involves identifying control measures to minimize the risk.
which dilution series differs by an equal interval
linear dilutions
which dilution series differs by a constant proportion
logarithmic dilutions
what is used to determine the concentration of a colored solution
Absorbance using suitable wavelength filters
what is used to determine turbidity
percentage transmission
what is a buffer solution
it is a mixture of compounds (often a weak acid and its base);
what is pH
it is a continuous scale and indicates the concentration of hydrogen ions
what is the purpose of a buffer
it resists small changes in pH, by the addition of an acid or alkalai
what does a colorimeter do
measures the passage of light through a solution or the absorbance of light by the solution
what is the affect of the addition of an acid or alkali on a buffer
Addition of acid or alkali has very small effects on the pH of a buffer, allowing the pH
of a reaction mixture to be kept constant.
what is a standard curve used for
Plotting measured values for known concentrations to produce a line or curve
allows the concentration of an unknown to be determined from the standard curve.
Method and uses of a colorimeter to quantify
concentration and turbidity
Calibration with appropriate blank as a baseline; use of absorbance to determine
concentration of a coloured solution using suitable wavelength filters; use of percentage transmission to determine turbidity, such as
cells in suspension.
how does a centrifuge separate components in a mixture
More dense components settle in the pellet; less dense components remain in the
supernatant.
what does the speed that each solute travel along the chromatogram depend on
The speed that each solute travels along the
chromatogram depends on its differing
solubility in the solvent used.
what is paper thin chromatography used for
Paper and thin layer chromatography can be
used for separating different substances such
as amino acids and sugars
what is a centrifuge used for
centrifuge to separate substances of
differing density
Principle of affinity chromatography and its
use in separating proteins
A solid matrix or gel column is created with
specific molecules bound to the matrix or gel.
Soluble, target proteins in a mixture, with a
high affinity for these molecules, become
attached to them as the mixture passes down
the column. Other non-target molecules with
a weaker affinity are washed out.
Principle of gel electrophoresis
Charged macromolecules move through an
electric field applied to a gel matrix. it is used to seperate protiens and nucleic acids
how do native gels seperate molecules
Native gels do not denature the molecule so
that separation is by shape, size and charge.
SDS–PAGE separates proteins
SDS–PAGE gives all the molecules an
equally negative charge and denatures them,
separating proteins by size alone.
define iso-electric point
IEP is the pH at which a soluble protein has
no net charge and will precipitate out of
solution.
If the solution is buffered to a specific pH, only the what will precipitate out
If the solution is buffered to a specific pH, only the protein(s) that have an IEP of that pH will precipitate
Soluble proteins can be separated using an
electric field and a what
Soluble proteins can be separated using an
electric field and a pH gradient. A protein
stops migrating through the gel at its IEP in the pH gradient because it has no net charge.
what are immunoassay techniques used to detect
Immunoassay techniques are used to detect
and identify specific proteins.These techniques use stocks of antibodies
with the same specificity, known as
monoclonal antibodies
An antibody specific to the protein antigen is linked to a chemical ‘label’. what is this ‘label’
An antibody specific to the protein antigen is linked to a chemical ‘label’. The ‘label’ is often a reporter enzyme producing a colour change, but chemiluminescence, fluorescence and other
reporters can be used.
in some cases assay uses what
In some cases the assay uses a specific
antigen to detect the presence of antibodies.
what is western blotting
Western blotting is a technique, used after
SDS–PAGE electrophoresis
The separated proteins from the gel are
transferred (blotted) onto a solid medium.
how can proteins be identified
The proteins can be identified using specific antibodies that have reporter enzymes
attached
what is bright feild commonly microscopy used for
Bright-field microscopy is commonly used to
observe whole organisms, parts of organisms, thin sections of dissected tissue
or individual cells
what is flourescence microscopy
Fluorescence microscopy uses specific
fluorescent labels to bind to and visualise
certain molecules or structures within cells or
tissues
what do aseptic techniques do
Aseptic technique eliminates unwanted
microbial contaminants when culturing microorganisms or cells
what do aseptic techniques involve
Aseptic technique involves the sterilisation of
equipment and culture media by heat or
chemical means and subsequent exclusion of
microbial contaminants.
how can a microbial culture be started
A microbial culture can be started using an
inoculum of microbial cells on an agar
medium, or in a broth with suitable nutrients
many culture media that exist do what
Many culture media exist that promote the
growth of specific types of cells and
microbes.
Animal cells are grown in medium containing what
Animal cells are grown in medium containing
growth factors from serum
what are growth factors
Growth factors are proteins that promote cell
growth and proliferation. Growth factors are
essential for the culture of most animal cells.
In culture, primary cell lines can divide a
limited number of times, whereas what
In culture, primary cell lines can divide a
limited number of times, whereas tumour
cells lines can perform unlimited divisions
Plating out of a liquid microbial culture on
solid media allows what
Plating out of a liquid microbial culture on
solid media allows the number of colony forming units to be counted and the density of cells in the culture estimated
what is serial dilution often needed for
Serial dilution is often needed to achieve a
suitable colony count
what is a haemocytometer used for
to estimate cell numbers in a liquid culture
what is vital staining required for
Vital staining is required to identify and count
viable cells
