Unit 1 - Key Area 1: Laboratory Techniques

Question 1

Explain what is meant by a hazard in the laboratory

Answer 1

Anything that poses a potential threat to an individual or the environment

Question 2

Give examples of hazards in the laboratory

Answer 2

Toxic or corrosive chemicals, heat or flammable substances, pathogenic organisms and mechanical equipment

Question 3

Explain what is meant by a risk in the laboratory

Answer 3

The likelihood of harm arising from exposure to a hazard

Question 4

What control measures might be put in place to minimise risk?

Answer 4

Appropriate handling techniques, protective clothing and equipment, aseptic technique

Question 5

Explain what is meant by a linear dilution series

Answer 5

Differ by an equal interval (eg 0.1, 0.2, 0.3)

Question 6

Explain what is meant by a log dilution series

Answer 6

Differ by a constant proportion (10-1, 10-2)

Question 7

Describe how a standard curve is produced

Answer 7

Plot measured values for known concentrations to produce a line or curve, allows the concentration of an unknown to be determined

Question 8

Describe the use of a buffer to control pH

Answer 8

Buffer is not affected by acid or alkali, so is used to keep the pH of a reaction mixture to be kept constant

Question 9

Describe the use of a colorimeter to quantify concentration

Answer 9

Absorbance is used to determine concentration of a coloured solution using suitable wavelength filters

Question 10

Describe the use of a colorimeter to quantify turbidity

Answer 10

Percentage transmission is used to determine turbity such as cells in suspension

Question 11

How is a centrifuge used to separate substances?

Answer 11

Centrifugation is used to separate by density. More dense components settle in the pellet, less dense remain in the supernatant

Question 12

What type of substances can be separated by paper or thin layer chromatography?

Answer 12

Amino acids and sugars

Question 13

What is the basic principle behind paper or thin layer chromatography?

Answer 13

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

Question 14

Describe how affinity chromatography works

Answer 14

A solid gel column is created wuith specific molecules bound to the matrix or gel. Soluble, target proteins in a mixture have a high affinity to these molecules and become attached as the mixture passes through

Question 15

Describe how gel electrophoresis works

Answer 15

Charged macromolecules move through an electric field applied to a gel matrix. Smaller pieces move faster and further than larger molecules

Question 16

Explain the difference between native gels and SDS-PAGE

Answer 16

Native gels do not denature the molecule so that separation is by shape, size and charge. SDS-PAGE gives all the molecules an equally negative charge and denatures them, separating by size alone

Question 17

Explain what is meant by the IEP of a protein

Answer 17

The pH at which a soluble protein has no net charge and will precipitate out of solution

Question 18

How can proteins be separated by IEP?

Answer 18

Solution is buffered tia specific oH, only the protein(s) that have an IEP of that pH will precipitate

Question 19

Describe the separation of proteins by IEP in electrophoresis

Answer 19

Soluble proteins can be separated using an electirc 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 20

What is meant by monoclonal antibodies?

Answer 20

Antibodies which have the same specificity

Question 21

Describe the use of an immunoassay to detect and identify proteins

Answer 21

An antibody specific to the protein antigen is linked to a chemical “label” which reacts when it binds with the antibody

Question 22

Give an example of the type of chemical label that might be used in an immunoassay

Answer 22

A reporter eznymbe producing a colour change, chemiluminescence or fluorescence

Question 23

Describe the use of a Western blot

Answer 23

After SDS-PAGE electophoresis, separated proteins from the gel are transferred onto a solid medium. Proteins can be idenitfied using specific antibodies attached to reported enzymes

Question 24

What is bright-field microscopy used for?

Answer 24

Observing whole organisms, parts of organisms, thin sections of dissected tissue or individual cells

Question 25

What is fluorescence microscopy used for?

Answer 25

Uses fluorescent labels to bind to and visualise certain molecules or structures within cells and tissues

Question 26

What is the purpose of aseptic technique?

Answer 26

To eliminate unwanted microbial contaminants when culturing micro-organisms or cells

Question 27

What is involved in aseptic technique?

Answer 27

Sterilisation of equipment and culture media by heat or chemical means

Question 28

What are the types of media used for growing a microbial culture?

Answer 28

A solid agar medium or in a broth with suitable nutrients

Question 29

What do animal cells require in a growth medium?

Answer 29

Growth factors which are proteins that promote cell growth and proliferation

Question 30

Describe the different growth of primary cell lines and tumour cell lines

Answer 30

Primary cell lines can divide a limited number of times wheras tumour cells can perform unlimited divisions

Question 31

How can the density of cells in a liquid culture be estimated?

Answer 31

By plating out onto a solid meia allowing the number of colony-forming units to be counted

Question 32

Describe the use of a haemocytometer

Answer 32

Counting the number of cells in a particular area of the grid, allows cell density to be calculated

Question 33

What is meant by a total cell count?

Answer 33

the number of cells in a culture

Question 34

What is meant by a viable cell count?

Answer 34

The number of living cells in a culture