practicals

Question 1

what is the definition of accuracy?

Answer 1

mean results are close together

Question 2

what is the definition of precision?

Answer 2

results having a small standard deviation

Question 3

What is the function of a stage micrometre?

Answer 3

To calibrate an eyebrows gratitude so that it can be used to make measurements.

Question 4

How is an eyepiece gratitude calibrated?

Answer 4

1. Select desired magnification and objective lens.
2. Place stage micrometre on the stage.
3. Line up the scales of the micrometre and the eyepiece graticule.
4. Count the number of divisions on the eye piece graticule equivalent to each division on this stage micrometre.
5. Calculate the length of one division of the eye piece graticule.

Question 5

Outline the procedure for preparing a slide.

Answer 5

1. stain sample
2. mount sample on slide
3. Place cover slip carefully on the slide, avoiding air bubbles.

Question 6

Why are plant tissues stained before they are observed?

Answer 6

So the different tissues can appear as different colours, making them more easily identifiable.

Question 7

How is percentage cover calculated?

Answer 7

1. place a quadrat
2. Count how many squares contain the required species.
3. Calculate this as a percentage of the whole quadrant.

Only count a square if more than half of the square is covered.

Question 8

Outline the procedure for random sampling.

Answer 8

1. Use a random number generator to generate 10 sets of random coordinates.
2. Use two tape measures to create a set of axes on which the coordinates can be read.
3. Place the quarter at each of the coordinates.
4. Record the percentage cover for the chosen species.

Question 9

What is species diversity

Answer 9

The number of different species in a community and the relative abundance of each population.

Question 10

Outline the procedure for using a transact for systematic sampling.

Answer 10

1. Use a measuring tape to make a transect over the area you wish to sample.
2. Place quadrats at given intervals along the tape measure.
3. Identify the different species in each contract using the key and count the number of each present.
4. Calculate percentage cover.

Question 11

How could you measure the rate of reaction using hydrogen peroxide and catalase?

Answer 11

Measure the volume of oxygen gas produced in a given time.

Question 12

Outline the procedure to find the effect of enzyme concentration on rate of reaction using amylase.

Answer 12

1. Put drops of iodine solution into each well of a spotting tile
2. Make a serial dilution of amylase to produce several concentrations.
3. At the same concentration and volume of starch to the first boiling tube and start the timer.
4. Using a dropping pippette put one drop of this mixture into one of the wells containing the iodine solution at regular intervals.
5. Time how long it takes for the colour to no longer be blue black.
6. Repeat at least two more times and calculate the mean time taken.
7. Repeat the experiment for each concentration of amylase.

Question 13

What is a colorimeter measure?

Answer 13

absorbance or transmission

Question 14

Outline the procedure to find an unknown concentration of reducing sugar.

Answer 14

1. Carry out a Benedict’s test on a range of standard solutions of reducing sugars.
2. Using the colorometer to measure the percentage absorbance for each sample.
3. Plot a graph of absorbance against reducing sugar concentration.
4. Carry out the Benedict’s test on the unknown solution and measure the absorbance using the colorometer.
5. Plot the absorbance on the calibration curve and read off the X axis for the concentration of the unknown solution.

Question 15

What is the purpose of chromatography?

Answer 15

To separate different components in a sample.

Question 16

What factors affect the rate of migration of different pigments during chromatography?

Answer 16

• solubility
• mass
• affinity to the paper

Question 17

Outline the procedure of using chromatography to separate photosynthetic pigments.

Answer 17

1. Draw a pencil line one centimetre above the bottom of the filter paper.
2. Use a capillary tube to transfer the pigment onto the pencil line.
3. Suspend their paper in the solvent so that the level of the liquid doesn’t lie above the pencil line and leave until the solvent has run up the paper to near the top.
4. Remove the paper from the solvent and draw a pencil line marking where the solvent move up to.
5. Calculate the Rf value for each spot.

Question 18

What should you also do when using chromatography to separate amino acids?

Answer 18

Spray the chromatography paper with NinHydrin solution to stain each residue purple.

Question 19

What is the purpose of gel electrophoresis?

Answer 19

To separate dna fragments.

Question 20

How does gel Electrophoresis work?

Answer 20

The negative charge of the phosphate groups in the dna are attracted to the anode. This means they move towards it. The shorter fragments will move at a faster rate.

Question 21

What are five examples of aseptic technique?

Answer 21

• wash your hands
• disinfect work area
• have bunsen burner flame on nearby
• flame the neck of the bacteria tube
• sterilise equpiment in flame before/after use

Question 22

Why is bacteria incubated at 25 degrees Celsius?

Answer 22

To prevent the growth of pathogens.

Question 23

Why are petri dishes incubated upside down?

Answer 23

To prevent condensation forming on the lead and dripping down onto the bacteria

Question 24

Outline the procedure to find the effect of antibiotics or bacterial growth?

Answer 24

1. Using a sterile pipette add the same volume of each antibiotic to different labelled petri dishes.
2. dip inoculating loop in the broth.
3. Spread a streak of the broth over the Agar surface. Then close the Petri dish and tape it shut.
4. Place Petri dishes in incubator and leave for the same amount of time.
5. Count the number of colonies that have formed on each plate

Question 25

Why should valid not be completely taped to the petri dish?

Answer 25

To allow some oxygen to enter, which will prevent the growth of harmful anaerobic bacteria.

Question 26

Outline the procedure to investigate the effect of temperature and permeability of cell membranes.

Answer 26

1. Cut beetroot into six identical cubes. 2, Place each cube in a different test tube with equal volumes of distilled water. 3. Place each test tube into water baths ranging from 30 to 80 degrees Celsius. Leave for 20 minutes. 4. Filter each solution into a cuvette and measure the absorbance using a colorimter

Question 27

what does biuret test for

Answer 27

protein

Question 28

Why is the colour change for biuret test?

Answer 28

blue --> purple

Question 29

What is Iodine's solution test for?

Answer 29

starch

Question 30

What is the colour change for iodine solution?

Answer 30

brown --> blue/black

Question 31

What does Benedict's reagent test for?

Answer 31

reducing sugars

Question 32

Outline the test for reducing sugars

Answer 32

1. Add equal volumes of Benedict's reagent to a sample and boil. 2. If positive, the colour changes from blue to red.

Question 33

What does an upward slope on the spirometer trace indicate?

Answer 33

breathing in

Question 34

Outline the test for producing non-reducing sugars.

Answer 34

1. add dilute HCl and boil 2. neutralise with Sodium hydrogen carbonate. 3. Add Benedict's reagent and boil 4. If positive colour changes from blue to red

Question 35

What does a downward slope on this spirometer trace indicate?

Answer 35

breathing out

Question 36

Outline the procedure to investigate the effect of exercise on heart rate.

Answer 36

1. measure resting heart rate 2. Do some gentle exercise then measure heart rate again. 3. Return to resting position. Measure heart rate every minute until it returns to the resting state. 4. Record time taken to return to normal. 5. Repeat using different people.

Question 37

How could you prepare the shoots when investigating phototropism?

Answer 37

1. cover tips with foil 2. cover base with foil 3. leave without foil

Question 38

Outline a procedure for investigating geotropism.

Answer 38

1. Line 3 Petri dishes with moist cotton wool. 2. Place 10 cress seeds on the surface of the wool and press them in slightly. 3. Put a lid on each dish and wrap in foil to prevent light reaching the seeds 4. Leave the dishes wherever temperature is constant and warm. 5. Set up the dishes so ther are placed at different angles. 6. Leave the seeds for 4 days. 7. After four days unwrap each dish and note the direction of the shoot and root growth.

Question 39

Outline the procedure to investigate the effect of auxin?

Answer 39

1. Select 30 plant similar in height, mass and age. 2. Count the number of side shoots growing from the main stem 3. Apply a paste with auxin to 10 plants, one without auxin to another 10, and leave the remaining 10 as they are. 4. Allow six days for the plants to grow. 5. Count the number of side shoots that have grown from the main stem.

Question 40

Outline the procedure to find the effect of gibberish on plants stem elongation.

Answer 40

1. select 40 plants of similar height, age and mass 2. leave 20 to grow, and water the other 20 with a dilute giberellin solution 3, leave plants for 28 days 4. Measure the length of the stem of the plants every seven days, and calcuate the mean stem length.

Question 41

How does a respirometer work?

Answer 41

When organisms respire in the chamber, they use oxygen, which causes pressure to decrease and liquid to move in the tube.