Sample Questions

Question 1

Give three examples of materials that are birefringent.

Answer 1

Quartz
Sapphires
Calcite
Ice

Question 2

What is meant by birefringent?

2

Answer 2

A material that refracts light in two directions - double refraction

This causes a double vision effect

Question 3

What is the magnification of your eyepiece lens?

Answer 3

x10

Question 4

What are the magnifications of your objective lenses?

Answer 4

x4
x10
x40
x100

Question 5

Name 3/4 of the major microscope brands.

Answer 5

Olympus
Nikon
Zeiss
Leitz

Question 6

What type of filters are used in fluorescent microscopes?

Answer 6

Exciter filter

Barrier filter

Question 7

What is the function of the exciter filter in a fluorescent microscope?

Answer 7

The exciter filter allows only a certain wavelength of light to pass through and reach the sample

Question 8

What is the function of the barrier filter in a fluorescent microscope?

Answer 8

The barrier filter allows a specific wavelength of light to pass through to the detector

Question 9

Name three anti-coagulants used for blood samples.

Answer 9

Sodium citrate
EDTA
Lithium heparin

Question 10

Why are anti-coagulants used?

Answer 10

To prepare the whole blood or the plasma

Question 11

What are the tests carried out on cerebro-spinal fluid to investigate infection (meningitis)?

Answer 11

Cytospin

Gram Staining

Question 12

Describe the process of cytospin.

Answer 12

Add couple drops of sample into the cytospin which compacts the sample into a dot on a slide - this concentrates the cellular material

Question 13

What category does staphylococcus aureus belong to?

Answer 13

Bacteria

Question 14

What category does myobacterium tuberculosis belong to?

Answer 14

Bacteria

Question 15

What category does HIV1 belong to?

Answer 15

Virus

Question 16

What category does plasmodium falciparum belong to?

Answer 16

Protozoan

Question 17

What is plasmodium falciparum commonly called?

Answer 17

Malaria

Question 18

What category does Ebola belong to?

Answer 18

Virus

Question 19

What category does meningitis belong to?

Answer 19

Virus or bacteria depending on the type

Question 20

Which is the more fatal type of meningitis, bacterial or viral?

Answer 20

Bacterial

Question 21

What type of bin should you dispose needles in?

Answer 21

Sharps

Question 22

What type of bin should you dispose latex gloves in

Answer 22

Yellow bags/biological waste bags

Question 23

What type of bin should you dispose paper in?

Answer 23

Black bag

Question 24

What type of bin should you dispose blood in?

Answer 24

Blood is drained down the sink, the container is either put in the yellow bag or the sharps bin depending on weather or not it is sharp

Question 25

What type of bin should you dispose glass in?

Answer 25

Sharps bin

Question 26

What type of bin should you dispose pipette tips in?

Answer 26

Sharps bin

Question 27

Why do we use blanks in spectrophotometry?

Answer 27

The 'blank' allows you to set the spectrophotometer to zero before you measure your 'unknown' solution

Question 28

What are blanks?

Answer 28

A blank is a sample that contains everything except for the analyte of interest

Question 29

How is it possible to use a spectrophotometer to measure a colourless compound? (2)

Answer 29

Even though the sample may appear colourless it may still emit a colour under ultraviolet or infrared light This is because the visible spectre lies between 400 and 700 nanometers while the ultraviolet spectre lies between 10 and 400 nanometres (infrared = 700nm to 1mm)

Question 30

What is the ultraviolet region? | 2

Answer 30

The range of light that exists between 10 and 400 nanometres It is invisible

Question 31

How can light be emitted from the ultraviolet region?

Answer 31

Tryptophan fluoresces when exposed to ultraviolet light Two double and two single bonds alternating in a molecule

Question 32

What is tryptophan?

Answer 32

An amino acid

Question 33

What do you do if optical density reading (absorbance is too high)? (4)

Answer 33

Dilute it one and two This new measured value should come within the standard curve Then double the value at the end E.g. find value for diluted sample then double it

Question 34

What experiment did you carry out to identify a faulty pipette? (4)

Answer 34

Set up weighing scales Weighed out the same amount of liquid (200ml) from each pipette The pipette with the amount closest to 0.2 gis correctly calibrated and the one with the amount furthest away is the faulty pipette This experiment is carry out on the basis that water has a density of 1g

Question 35

How can temperature affect pipetting? | 3

Answer 35

Water expands at high temperatures Therefore if one measures an amount of water when it is cold, the volume will have changed when the water is warmed up Temperature also affects the air - less of a vacuum at higher temperatures

Question 36

What type of pipette would you use for viscous, dense or volatile liquids (ether or ethanol) and why? (3)

Answer 36

You would use a positive displacement pipette The piston comes in contact with the liquid A vacuum is not used

Question 37

Why is it important to wet the tip 2-3 times with solution before carrying out experiment? (2)

Answer 37

To moisten inside of tip 2-3 times Evaporation could occur otherwise when using very small volumes which reduces the risk of getting an inaccurate result

Question 38

What does the Beer Lambert Law tell us about the relationship between absorbance and concentration?

Answer 38

Absorbance is proportional to concentration except at low and high concentrations

Question 39

Why do we need to calibrate the pH meter? | 4

Answer 39

The meter consists of a pair of metal electrodes When metal is left in solution it oxidises This causes the electrode to erode Therefore we calibrate daily to take into account this erosion

Question 40

Why are buffers important in biology? | 2

Answer 40

Buffers are important to keep pH between 7.35 and 7.45 in the human body Without buffers enzyme reactions wouldn't occur

Question 41

What is the relationship between [H+] in mol?L and pH?

Answer 41

Inversely proportional i.e. as the hydrogen ion concentration increases the pH goes down

Question 42

Why did the acidic stain work better? | 2

Answer 42

Exposes tissues Acid corrodes the tissue and allows better bonding to the sample