Key Area 1

Question 1

What is a hazard?

Answer 1

Anything which can cause harm

Question 2

What is risk?

Answer 2

Risk is the likelihood of harm arising from exposure to a hazard.

Question 3

What does a risk assessment involve?

Answer 3

Identifying control measures to minimise the risk

Question 4

What are some hazards in the lab?

Answer 4

Toxic or corrosive chemicals
Heat or flammable substances
Pathogenic organisms
Mechanical equipment

Question 5

What do linear dilutions range by?

Answer 5

Equal intervals e.g. 0.1ml , 0.2ml

Question 6

What do log dilutions range by?

Answer 6

Differ by a constant proportion e.g 10-1, 10-2, 10-3 etc

Question 7

What is pH?

Answer 7

A measure of the hydrogen ion concentration in a solution

Question 8

What is a colorimeter used for?

Answer 8

To measure the concentration of a coloured solution or the turbidity(cloudiness)

Question 9

What does centrifugation separate substances by?

Answer 9

Density

Question 10

What does the pellet and supernatant contain?

Answer 10

Pellet: densest materials at bottom of tube
Supernatant: less dense materials remain in liquid above pellet

Question 11

What does chromatography do?

Answer 11

Allows scientists to identify and/or purify the components of a mixture

Question 12

What are the 3 types of chromatography?

Answer 12

Paper chromatography
Thin layer chromatography
Affinity chromatography

Question 13

What is paper and thin layer chromatography?

Answer 13

When a sample of the picture is being separated is placed in a dot near the bottom of a strip of chromatography paper, which is then placed in a solvent.

Question 14

How is the Rf value calculated?

Answer 14

Rf = distance travelled by dot/ distance travelled by solvent

Question 15

What is affinity chromatography?

Answer 15

It is used to separate target proteins

Question 16

What is the process of affinity chromatography?

Answer 16

Solid matrix or gel column created with specific molecules bound to matrix or gel. Soluble, target proteins with high affinity for these molecules become attached and non-target molecules with a weaker affinity are washed out.

Question 17

What does gel electrophoresis do?

Answer 17

Separates proteins and nucleic acids based upon their:
Charge
Shape
Size

Question 18

What is isoelectric point?

Answer 18

The isoelectric point of a protein is the pH at which it has no net charge. At this pH the protein will precipitate out of the solution.

Question 19

Features and properties of antibodies?

Answer 19

Made by b-lymphocytes
Specific to one type of antigen(foreign proteins found on microbes)
Each lymphocyte makes one specific antibody which will bind to one specific antigen and make the antigen harmless

Question 20

What are immunoassy techniques used for?

Answer 20

To detect and identify specific proteins. Can use antigens to detect antibodies or vice versa.

Question 21

Process of antibodies detecting antigens?

Answer 21

Stocks of antibodies with the same specificity, known as monoclonal antibodies. Antibody specific to target antigen bound to surface of multiwell plate. Same is added and if farther antigen is present it will bind to antibody.

Question 22

How to know if the antigen has bound?

Answer 22

Another antibody specific to the antigen is added and 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 23

Antigens to detect antibodies?

Answer 23

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

Question 24

What is western blotting?

Answer 24

A technique used after SDS-PAGE electrophoresis

Question 25

What can identify proteins?

Answer 25

Specific antibodies that have reporter enzymes attached

Question 26

What are the 2 types of microscopy?

Answer 26

Bright field microscopy Fluorescence microscopy

Question 27

What is bright field microscopy?

Answer 27

Form of microscopy commonly used to observe: Whole organisms Parts of organisms Thing sections of dissected tissue or individual cells Lower resolution.

Question 28

What is fluorescence microscopy?

Answer 28

Form of microscopy that uses specific fluorescent labels to bring to and visualise certain molecules or structure within cells or tissue. Higher resolution.

Question 29

What are aseptic techniques?

Answer 29

Techniques that eliminate unwanted microbial contaminants when culturing microorganisms or cells.

Question 30

What does aseptic technique involve?

Answer 30

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

Question 31

What are examples of aseptic techniques?

Answer 31

- Wear a lab coat - Throughly wash hands - Smooth, in-absorbent work surface with disinfectant - Autoclave or pressure cooker to sterilise glassware - sterile petri dishes of nutrient agar - wire loop flames before use to destroy unwanted microbes - bin lined with plastic bag for safe disposal of used plates

Question 32

What is cell culture?

Answer 32

The ability to grow cells in an artificial laboratory environment. E.g culturing mammalian cells for cancer studies

Question 33

How can a microbial culture be started?

Answer 33

Can be started by using an inocululm of microbial cells in an agar medium or in a broth with suitable nutrients.

Question 34

What do plant and animal cell cultures require?

Answer 34

Require complex culture media which contain all the requirements of the cells

Question 35

What are typical culture media?

Answer 35

Water Salts Amino acids Vitamins Glucose

Question 36

What are growth factors?

Answer 36

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

Question 37

What is a cell line?

Answer 37

A genetically uniform cell culture developed from a single cell. Primary cell lines can divide a limited number of times. Tumour cells can perform unlimited divisions.

Question 38

What does plating out allow?

Answer 38

Playing out of a liquid microbial culture in solid media allows the number of colons forming units to be counted and the density is the cells in the culture estimated.

Question 39

What is a haemocytometer?

Answer 39

A haemocytometer allows an estimation of the number of cells in the sample to be made. It resembles a specialised microscope slide.

Question 40

How can the reliability of results be improved?

Answer 40

The number of cells should be counted and an average calculated

Question 41

Disadvantages of using a haemocytometer?

Answer 41

- Dead cellls are not distinguished from live cells (unless stained) - small cells are difficult to locate - time consuming - numbers obtained are only an estimate

Question 42

Total and viable cell count

Answer 42

A haemocytometer can be used to provide an estimate of both the total and viable cell number.

Question 43

What is the viable cell count?

Answer 43

The number of live actively growing/dividing cells in a sample

Question 44

What is the total cell count?

Answer 44

The number of dead and live cells

Question 45

What is trypan blue dye used for?

Answer 45

It is taken up by dead cells but not by living cells. A viable cell count can be performed where only unstained cells are counted.

Question 46

How is a total cell count performed?

Answer 46

It is performed by counting up all of the cells, including those with trypan blue.