lab techniques

Question 1

define risk

Answer 1

the likelihood of harm arising from exposure to a hazard

Question 2

what are the types of hazard?

Answer 2

toxic or corrosive chemicals, heat or flammable substance, pathogenic organisms and mechanical equipment

Question 3

what control measures are used to control risk

Answer 3

appropriate handling techniques,protective clothing and equipment and aseptic techniques

Question 4

What does risk assessment involve?

Answer 4

involves identifying control measures to minimize the risk.

Question 5

which dilution series differs by an equal interval

Answer 5

linear dilutions

Question 6

which dilution series differs by a constant proportion

Answer 6

logarithmic dilutions

Question 7

what is used to determine the concentration of a colored solution

Answer 7

Absorbance using suitable wavelength filters

Question 8

what is used to determine turbidity

Answer 8

percentage transmission

Question 9

what is a buffer solution

Answer 9

it is a mixture of compounds (often a weak acid and its base);

Question 10

what is pH

Answer 10

it is a continuous scale and indicates the concentration of hydrogen ions

Question 11

what is the purpose of a buffer

Answer 11

it resists small changes in pH, by the addition of an acid or alkalai

Question 12

what does a colorimeter do

Answer 12

measures the passage of light through a solution or the absorbance of light by the solution

Question 13

what is the affect of the addition of an acid or alkali on a buffer

Answer 13

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.

Question 14

what is a standard curve used for

Answer 14

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.

Question 15

Method and uses of a colorimeter to quantify
concentration and turbidity

Answer 15

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.

Question 16

how does a centrifuge separate components in a mixture

Answer 16

More dense components settle in the pellet; less dense components remain in the
supernatant.

Question 17

what does the speed that each solute travel along the chromatogram depend on

Answer 17

The speed that each solute travels along the
chromatogram depends on its differing
solubility in the solvent used.

Question 18

what is paper thin chromatography used for

Answer 18

Paper and thin layer chromatography can be
used for separating different substances such
as amino acids and sugars

Question 19

what is a centrifuge used for

Answer 19

centrifuge to separate substances of
differing density

Question 20

Principle of affinity chromatography and its
use in separating proteins

Answer 20

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.

Question 21

Principle of gel electrophoresis

Answer 21

Charged macromolecules move through an
electric field applied to a gel matrix. it is used to seperate protiens and nucleic acids

Question 22

how do native gels seperate molecules

Answer 22

Native gels do not denature the molecule so
that separation is by shape, size and charge.

Question 23

SDS–PAGE separates proteins

Answer 23

SDS–PAGE gives all the molecules an
equally negative charge and denatures them,
separating proteins by size alone.

Question 24

define iso-electric point

Answer 24

IEP is the pH at which a soluble protein has
no net charge and will precipitate out of
solution.

Question 25

If the solution is buffered to a specific pH, only the what will precipitate out

Answer 25

If the solution is buffered to a specific pH, only the protein(s) that have an IEP of that pH will precipitate

Question 26

Soluble proteins can be separated using an electric field and a what

Answer 26

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.

Question 27

what are immunoassay techniques used to detect

Answer 27

Immunoassay techniques are used to detect and identify specific proteins.These techniques use stocks of antibodies with the same specificity, known as monoclonal antibodies

Question 28

An antibody specific to the protein antigen is linked to a chemical ‘label’. what is this 'label'

Answer 28

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.

Question 29

in some cases assay uses what

Answer 29

In some cases the assay uses a specific antigen to detect the presence of antibodies.

Question 30

what is western blotting

Answer 30

Western blotting is a technique, used after SDS–PAGE electrophoresis The separated proteins from the gel are transferred (blotted) onto a solid medium.

Question 31

how can proteins be identified

Answer 31

The proteins can be identified using specific antibodies that have reporter enzymes attached

Question 32

what is bright feild commonly microscopy used for

Answer 32

Bright-field microscopy is commonly used to observe whole organisms, parts of organisms, thin sections of dissected tissue or individual cells

Question 33

what is flourescence microscopy

Answer 33

Fluorescence microscopy uses specific fluorescent labels to bind to and visualise certain molecules or structures within cells or tissues

Question 34

what do aseptic techniques do

Answer 34

Aseptic technique eliminates unwanted microbial contaminants when culturing microorganisms or cells

Question 35

what do aseptic techniques involve

Answer 35

Aseptic technique involves the sterilisation of equipment and culture media by heat or chemical means and subsequent exclusion of microbial contaminants.

Question 36

how can a microbial culture be started

Answer 36

A microbial culture can be started using an inoculum of microbial cells on an agar medium, or in a broth with suitable nutrients

Question 37

many culture media that exist do what

Answer 37

Many culture media exist that promote the growth of specific types of cells and microbes.

Question 38

Animal cells are grown in medium containing what

Answer 38

Animal cells are grown in medium containing growth factors from serum

Question 39

what are growth factors

Answer 39

Growth factors are proteins that promote cell growth and proliferation. Growth factors are essential for the culture of most animal cells.

Question 40

In culture, primary cell lines can divide a limited number of times, whereas what

Answer 40

In culture, primary cell lines can divide a limited number of times, whereas tumour cells lines can perform unlimited divisions

Question 41

Plating out of a liquid microbial culture on solid media allows what

Answer 41

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

Question 42

what is serial dilution often needed for

Answer 42

Serial dilution is often needed to achieve a suitable colony count

Question 43

what is a haemocytometer used for

Answer 43

to estimate cell numbers in a liquid culture

Question 44

what is vital staining required for

Answer 44

Vital staining is required to identify and count viable cells