Unit 1.1 - Laboratory Techniques for Biologists

Question 1

Name hazards in a lab

Answer 1

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

Question 2

Define risk and what could be done to minimise it

Answer 2

Risk is the likelihood of harm arising from a hazard.
To minimise risk a risk assessment is used to identify control measures

Question 3

What is the difference between linear and log dilutions?

Answer 3

Linear dilution - series differ by an equal interval
Log dilution - series differ by a constant proportion

Question 4

What is a standard curve?

Answer 4

Measured values for known concentrations are plotted to produce a line or curve allowing the concentration of an unknown to be determined

Question 5

During colorimetry when is absorbance and percentage transmission used?

Answer 5

Absorbance - to determine the concentration of a coloured solution using suitable wavelength filters
Percentage transmission - determine turbidity

Question 6

Define turbidity

Answer 6

The cloudiness of a fluid caused by a large number of particles

Question 7

When using a centrifuge, what components go in the pellet and supernatant?

Answer 7

Pellet - More dense components
Supernatant - Less dense components remain here

Question 8

How can paper and thin layer chromatography be used to separate different substances such as amino acids and sugars?

Answer 8

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

Question 9

How does affinity chromatography work?

Answer 9

A solid matrix or gel column is created with specific molecules bound to the matrix of gel. Soluble target proteins have a high affinity for these molecules and become attached to them as the mixture passes down the column . Other non-target molecules are washed out

Question 10

How does gel electrophoresis work?

Answer 10

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

Question 11

How do native gels separate proteins?

Answer 11

Don’t denature molecules so the separation is based on shape, size and charge

Question 12

How does SDS-PAGE separate proteins?

Answer 12

Gives all molecules an equally negative charge and denatures them, separating the proteins based on size alone

Question 13

What is an isoelectric point (IEP)?

Answer 13

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

Question 14

How can IEPs be used in electrophoresis?

Answer 14

Soluble proteins can be separated using an electric field and a pH gradient. A protein will stop moving through the gel at its IEP in the pH gradient as it will have no net charge

Question 15

What are immunoassay techniques used for?

Answer 15

To detect and identify specific proteins

Question 16

How do immunoassay techniques work?

Answer 16

Uses stocks of antibodies with the same specificity (monoclonal antibodies). 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 17

What is western blotting?

Answer 17

A technique used after SDS-PAGE electrophoresis where the separated proteins are transferred onto a solid medium. The proteins can then be identified using specific antibodies that have reporter enzymes attached

Question 18

Define bright-field microscopy

Answer 18

Commonly used to observe whole organisms, parts of organisms, thin sections of dissected tissue or individual cells

Question 19

Define fluorescence microscopy

Answer 19

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

Question 20

What is the purpose of aseptic technique?

Answer 20

Eliminates unwanted microbial contaminants when culturing microorganisms or cells

Question 21

How is a microbial culture started?

Answer 21

Using an inoculum of microbial cells on an agar medium or broth with suitable nutrients to promote the growth of specific types of cells and microbes

Question 22

What is in the medium animal cells are grown in?

Answer 22

Serum which contains growth factors which are proteins that promote cell growth and proliferation

Question 23

Differences between primary cell lines and tumour cell line

Answer 23

Primary - can divide a limited number of times
Tumour - can perform unlimited divisions

Question 24

How can the number of colony forming units be counted and the density of cells in a culture counted?

Answer 24

Plating out of a liquid microbial culture on to solid media. A serial dilution is often needed to achieve a suitable colony count

Question 25

What is vital staining used for?

Answer 25

Required to identify and count viable cells