Unit 1 - Laboratory Techniques for Biologists

Question 1

What are some examples of hazards in a lab?

Answer 1

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

Question 2

How are control measures to minimise risks and reduce hazards identified?

Answer 2

Carrying out a risk assessment.

Question 3

What is risk?

Answer 3

The likelihood of harm arising from exposure to a hazard.

Question 4

What are some examples of risk control measures?

Answer 4

Using appropriate handling techniques, protective clothing and equipment, and aseptic technique.

Question 5

What are linear dilutions?

Answer 5

Dilutions that differ by an equal interval, eg 0.1, 0.2, 0.3 …

Question 6

What are log (serial) dilutions?

Answer 6

Dilutions that differ by a constant proportion, eg 0.1, 0.01, 0.001 …

Question 7

What is a standard curve used for?

Answer 7

To determine unknown values from a line or curve made with measured values.

Question 8

What is a buffer solution?

Answer 8

A solution where adding acids or alkalis has very small effects on the pH. Allows pH of a reaction mixture to be kept constant.

Question 9

What are colorimeters used to measure?

Answer 9

Concentration and turbidity (cloudiness).

Question 10

What must be done before using a colorimeter?

Answer 10

The colorimeter must be calibrated with an appropriate blank sample to provide a baseline reading.

Question 11

What can absorbance on a colorimeter be used to determine?

Answer 11

Concentration of a solution.

Question 12

What can percentage transmission on a colorimeter be used to determine?

Answer 12

Turbidity such as cells in suspension.

Question 13

What does a centrifuge separate substances according to?

Answer 13

Density.

Question 14

What do more dense components form in a centrifuge?

Answer 14

Pellet.

Question 15

What do less dense components form in a centrifuge?

Answer 15

Supernatant.

Question 16

How does paper and thin layer chromatography separate substances?

Answer 16

By solubility in the solvent used - speed that each solute travels along the chromatogram depends on solubility in the solvent.

Question 17

What is affinity chromatography used to separate?

Answer 17

Proteins from a mixture.

Question 18

Explain the process of affinity chromatography.

Answer 18

A solid matrix or gel column is created with specific molecules (usually receptors) bound to it. Soluble, target proteins in a mixture, with a high affinity for these molecules, become attached to them as the mixture moves down the column. Other molecules with a weaker affinity are washed out.

Question 19

What is gel electrophoresis used to separate?

Answer 19

Proteins and nucleic acids.

Question 20

How does gel electrophoresis work?

Answer 20

Charged macromolecules move through an electric field applied to a gel matrix.

Question 21

What do native gels in gel electrophoresis separate proteins by and how do they do this?

Answer 21

Shape, size and charge. They do not denature the molecule.

Question 22

What does SDS-PAGE separate proteins by and how?

Answer 22

Size.

Gives all molecules an equally negative charge and denatures them.

Question 23

What is the isoelectric point of a protein?

Answer 23

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

Question 24

What is the name given to the techniques used to detect and identify specific proteins?

Answer 24

Immunoassay.

Question 25

What are stocks of antibodies with the same specificity known as?

Answer 25

Monoclonal antibodies.

Question 26

What is the chemical ‘label’ used in immunoassay?

Answer 26

It is often a reporter enzyme producing a colour change but chemiluminescence, fluorescence and other reporters can be used.

Question 27

When is western blotting used?

Answer 27

After SDS-PAGE electrophoresis.

Question 28

Explain the process of western blotting.

Answer 28

Once the proteins have been separated in the gel they are transferred or blotted onto a solid medium. The proteins can then be identified using specific antibodies with reporter enzymes attached (ELISA).

Question 29

What 4 things is bright field microscopy commonly used to observe?

Answer 29

Whole organisms, parts of organisms, thin sections of dissected tissue or individual cells.

Question 30

How does fluorescence microscopy work?

Answer 30

It uses specific fluorescent labels to bind to and visualise certain molecules or structures within cells or tissues.

Question 31

What is aseptic technique?

Answer 31

Procedures used in laboratories to reduce contamination and unwanted growth or spread of microorganisms.

Question 32

What does the aseptic technique involve?

Answer 32

Sterilisation of equipment and culture media by heat or chemical means (to remove microbial contaminants).

Question 33

How can a microbial culture be started?

Answer 33

Using an inoculum of microbial cells on an agar medium or in a broth with suitable nutrients.

Question 34

What are animal cells grown in?

Answer 34

Medium containing growth factors from serum.

Question 35

What cell lines can divide a limited number of times?

Answer 35

Primary.

Question 36

What cell lines can perform unlimited divisions?

Answer 36

Tumour.

Question 37

What are growth factors?

Answer 37

Proteins that promote cell growth and proliferation. They are essential for the culture of most animal cells.

Question 38

What is used to estimate cell numbers in a liquid culture?

Answer 38

Haemocytometer.

Question 39

What is required to identify and count viable (living, respiring) cells?

Answer 39

Vital staining.

Question 40

What is the process in isoelectric point electrophoresis?

Answer 40

Two proteins with differing IEP’s loaded into a gel matrix
Proteins migrate towards the charges until they reach an area with the pH of their IEP
Proteins stop migrating as they have no charge and precipitate out