1.1 Laboratory Techniques

Question 1

Describe the difference between linear and log dilutions.

Answer 1

Linear dilutions differ by an equal interval, where as log dilution differ by a constant proportion.

Question 2

State when linear and log dilution may be used.

Answer 2

Linear dilutions are used to vary an independent variable, where as log dilutions are used to identify the optimum colony count.

Question 3

State the purpose of a standard curve

Answer 3

To identify the concentration of an unknown solution.

Question 4

State the purpose of buffers.

Answer 4

To maintain the pH of a solution, despite what acids or alkalis are added.

Question 5

What is the purpose of colorimetry?

Answer 5

To measure the concentration of a solution, using light absorbance.

Question 6

State the purpose of centrifugation.

Answer 6

To separate organelles based on density.

Question 7

Describe the principle of affinity chromatography.

Answer 7

Immobilised molecules within a gel matrix have a high affinity for a target protein. The target protein binds to the immobilised molecule, while non target molecules pass through the column. The target protein can then be eluded from the gel matrix in its purest form.

Question 8

Name the two types of molecules that can be separated by gel electrophoresis.

Answer 8

Nucleic acid and proteins.

Question 9

Compare similarities and differences between SDS and native gels.

Answer 9

SDS separates molecules based on molecular weight, where as native separates molecules based on size, shape and charge.

Question 10

Define IEP, and what happens when a protein reaches its IEP.

Answer 10

Iso-electric point. The point at which a protein has no net charge, and therefore precipitates out the solution.

Question 11

Describe the two stages of electric focusing.

Answer 11

First, proteins are introduced to an electrically charged gel matrix, and once the protein reaches its IEP it will precipitate out of the gel. Proteins will then be separated by size using standard gel electrophoresis, as larger proteins will be retained.

Question 12

What is a monoclonal antibody.

Answer 12

An antibody specific to one antigen.

Question 13

Compare indirect and sandwich ELISA protocols.

Answer 13

Indirect ELISA involves a 96 well plate being lined with an antigen, then having an antibody added. This is followed by a secondary antibody with a label, that will allow detection is the presence is detected, where as sandwich ELISA involves a 96 well plate being coated with a monoclonal antibody, and antigen being added, then a secondary antibody with a label being, allowing detection of the antigens presence.

Question 14

Compare bright-field microscopy and fluorescent microscopy.

Answer 14

Bright-field involves the use of white light to view samples, where as fluorescent microscopy involves monoclonal antibodies and secondary antibodies with labels with fluorescent molecules that can be detected by UV light.

Question 15

Why is it essential to add growth media when carrying out animal cell culture?

Answer 15

Growth factors promote cell growth and proliferation.

Question 16

Compare similarities and differences between tumour and primary cells.

Answer 16

Both are used in animal cell cultures, however while a tumour cell will divide an unlimited number of times, the primary cell will only divide a certain number of times before dying.

Question 17

Discuss the advantages of serial dilution prior to plating out microbial cells.

Answer 17

Allows scientists to count the number of colony forming from a sample, however a too high colony cannot be counted, and a too low colony count means the method must be reviewed.

Question 18

State the purpose of aseptic technique.

Answer 18

To prevent bacterial contamination.

Question 19

State two approaches that should be used when using aseptic technique

Answer 19

Chemical and flame.

Question 20

What is a haecytometer used for.

Answer 20

To ESTIMATE the number of cells in a sample.

Question 21

Describe how viable cell counts are carried out.

Answer 21

Tripan blue is added to the sample, and all blue stained cells are subtracted from the total cell count.