1.1 lab techniques for biologists

Question 1

what do risk assessments involve?

Answer 1

identifying hazards and implementing control measures to minimise the risk

Question 2

what can control measures include?

Answer 2

handling techniques
PPE
aseptic techniques

Question 3

what is the use of a burette?

Answer 3

to dispense precise volumes of liquid reagents

Question 4

what is dilation?

Answer 4

reducing the concentration of a substance in a solution

Question 5

what is serial dilution?

Answer 5

repeated dilution from a stock solution

Question 6

how do linear dilutions work?

Answer 6

Dilutions differ by an equal interval

Question 7

how do logarithmic dilutions work?

Answer 7

Dilutions differ by a
constant proportion

Question 8

what is a colorimeter used for?

Answer 8

to determine the concentration of a pigmented compound

Question 9

how does a colorimeter work?

Answer 9

it passes a light beam at a specific wavelength through a cuvette containing the sample solution
it measures the absorbance of this wavelength by the solution

Question 10

how does a standard curve work to determine unknown concentrations?

Answer 10

a series of standards of known concentrations are measured and graphed
this graph is used to determine the concentration of an unknown sample

Question 11

what is a pH buffer solution?

Answer 11

a solution whose pH changes very little when a small quantity of acid or base is added to it

Question 12

how do buffers work?

Answer 12

they allow the addition of hydrogen/hydroxide ions without affecting the pH of the solution

Question 13

according to which factors can substances be separated?

Answer 13

according to their
solubility
size
shape
charge

Question 14

how does centrifugation separate substances?

Answer 14

according to their size

Question 15

how do the largest and densest substances behave in a centrifuge?

Answer 15

they separate first and form a pellet at the bottom of the centrifuge

Question 16

what is the name given to the liquid remaining at the top of the centrifuge?

Answer 16

the supernatant

Question 17

describe proteins at their iso-electric point (a specific pH)

Answer 17

overall neutral charge and precipitate out of solution

Question 18

describe the charges of proteins above and below their isoelectric point

Answer 18

positive charge at pH below their IEP
negative charge at pH above their IEP

Question 19

what happens during isoelectric focussing?

Answer 19

a solution is buffered to a specific pH and only proteins with that IEP will precipitate

Question 20

how does electrophoresis separate molecules?

Answer 20

based on their charge, size and shape

Question 21

how does protein electrophoresis work?

Answer 21

current flows through a buffer
the gel acts as a sieve, separating the proteins

Question 22

which factors does SDS-PAGE separate proteins based upon?

Answer 22

size only - proteins are denatured and given a uniform charge

Question 23

which factors affect protein migration in gel electrophoresis?

Answer 23

size and charge (shape if proteins are not denatured beforehand)

Question 24

what does gel electrophoresis separate?

Answer 24

proteins and nucleic acids

Question 25

what does chromatography separate?

Answer 25

mixtures of amino acids and sugars

Question 26

the speed that each solute travels along the chromatogram depends on...

Answer 26

its solubility in the solute

Question 27

how does affinity chromatography work?

Answer 27

a ligand is immobilised and bound to a matrix of a gel column a target protein which is complementary to the ligand (strong affinity) will bind to it and remain in the column while the others are washed away (weak affinity) target protein can then be separated and purified

Question 28

what is the purpose of an immunoassay?

Answer 28

to produce antibodies and use them to identify proteins

Question 29

which antibodies are used in an immunoassay?

Answer 29

stocks of antibodies with the same specificity (monoclonal)

Question 30

how do immunoassays work?

Answer 30

the antibody specific to the antigen is linked to a chemical label

Question 31

what is usually used as a chemical label?

Answer 31

a reporter enzyme that produces a colour change

Question 32

how can the immunoassay process be used in an alternative way?

Answer 32

by using the antigen to detect the antibody

Question 33

what is the purpose of protein/western blotting?

Answer 33

to detect proteins from a tissue or cell extract

Question 34

how does protein/western blotting work?

Answer 34

after SDS-PAGE, the separated proteins from the gel are transferred onto a solid medium and can be identified using specific antibodies with reporter enzymes attached

Question 35

how does bright-field microscopy work?

Answer 35

a sample is mounted on a slide and illuminated from below the sample will often be stained beforehand to increase contrast

Question 36

how does fluorescence microscopy work?

Answer 36

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

Question 37

what is the purpose of a haemocytometer?

Answer 37

to estimate the concentration of cells in a sample

Question 38

describe the process of using a haemocytometer

Answer 38

- cell culture counted and gently mixed - some pipetted under a coverslip and haemocytometer placed under a microscope - cells within one of the 1mm x 1mm areas and counted

Question 39

what does the count of cells in the 1mm x 1mm square provide an estimate of?

Answer 39

the number of cells per 0.1 microlitres of culture medium

Question 40

how do you get the number of cells per microlitre?

Answer 40

multiply by 10

Question 41

how do you get the number of cells per cubic centimetre?

Answer 41

multiply by 10000

Question 42

how can the reliability of the results be affected when using a glass haemocytometer and why?

Answer 42

by incorrect placement of the coverslip - this provides a chamber with unknown volume

Question 43

how can viable cell counts be estimated?

Answer 43

using vital staining

Question 44

what is serial dilution sometimes needed for?

Answer 44

to achieve a suitable colony count

Question 45

what is cell culture?

Answer 45

the ability to grow cells in an artificial laboratory environment

Question 46

which process require cell culture?

Answer 46

growing bacterial cells culturing mammalian cells cancer studies

Question 47

what does typical cell culture media contain?

Answer 47

water, salts, amino acids, vitamins and glucose

Question 48

what does animal cell culture contain that plant does not?

Answer 48

growth factors from serum

Question 49

what is the purpose of growth factors?

Answer 49

to promote cell growth and proliferation

Question 50

how can a microbial culture be started?

Answer 50

using an inoculum of microbial cells on an agar medium/ broth with suitable nutrients

Question 51

how many times can primary cell lines divide?

Answer 51

a limited number

Question 52

how many times can tumour cell lines divide?

Answer 52

unlimited times

Question 53

what is the aim of aseptic techniques?

Answer 53

the keep the culture free from microorganisms and bacteria

Question 54

what are the essential aspects of aseptic techniques?

Answer 54

sterile work area sterile reagents and media sterile handling

Question 55

how can equipment and culture media be sterilised?

Answer 55

by heat or chemicals