Practical

Question 1

*

Answer 1

**INT

Question 2

1- Food tests

Answer 2

 Reducing sugars
 Non-reducing sugars
 Proteins
 Starch
 Fats and oils

Question 3

1- Food tests

apparatus

Answer 3

5 boiling tubes
2 test tubes
1 beaker
3 dropping pipettes
Benedict’s reagent
Dilute hydrochloric acid (0.5 mol dm-3)
Dilute sodium hydroxide/ sodium bicarbonate
Biuret reagent
Iodine- potassium iodide solution
Absolute alcohol
Glucose solution
Sucrose solution
Albumen solution
Starch solution
Oil
Water bath

Question 4

1- Food tests

Method

Reducing Sugars

Answer 4

Reducing sugars
1. Mix 2cm3 of the test solution with an equal volume of Benedict’s reagent.
2. Heat the mixture in a water bath to between 70oC and 90oC for 5 minutes
3. Record your observations.
Food tests
Specification reference: 1.1
Chemical elements are joined together to form biological compounds
12

Question 5

1- Food tests

Method

Non-reducing sugars

Answer 5

Non-reducing sugars
1. Mix 2cm3
of the test solution with an equal volume of Benedict’s reagent.
2. Heat the mixture in a water bath to between 70 oC and 90oC.
3. Observe and record colour change.
4. Put another 2cm3
of the test solution into a boiling tube, add 2 drops of hydrochloric
acid and heat in a water bath to 70 oC and 90 oC for 2 minutes.
5. Add 2 drops of sodium hydroxide/ small spatula of sodium bicarbonate.
6. Add 2cm3 Benedict’s reagent.
7. Heat the mixture in a water bath to between 70oC and 90oC for 5 minutes.
8. Record your observations

Question 6

1- Food tests

Method

Proteins

Answer 6

1. Mix 2 cm3
   of the test solution with 2 cm3
   of Biuret reagent in a boiling tube.
2. Cover the top of the boiling tube and invert it once.
3. Record your observations.

Question 7

1- Food tests

Method

Starch

Answer 7

1. Mix 2cm3
   of the test solution with 2 drops of iodine in potassium-iodide solution.
2. Record the colour change

Question 8

1- Food tests

Method

Fats and Oils

Answer 8

1. Mix the fat or oil with 5 cm3
   of absolute alcohol in a boiling tube.
2. Shake the tube.
3. Pour the mixture into another boiling tube half full of cold water.
4. Record your observations.

Question 9

2 - Preparation and scientific drawing of a slide of onion cells
including calibration of actual size and magnification of drawing

Answer 9

Apparatus

Microscope fitted with an eye piece graticule
Microscope slide and cover slip
Onion
Paper towel
Scalpel
White tile
Mounted needle
Iodine solution
Forceps

Question 10

2 - Preparation and scientific drawing of a slide of onion cells
including calibration of actual size and magnification of drawing

Answer 10

Method
1. Place two drops of water onto a microscope slide.
2. Take a small piece of onion and using forceps peel off the membrane from the
underside (the rough side).
3. Lay a piece of the membrane flat on the surface of the slide taking care that it is a
single layer and not folded back on itself.
4. Add three drops of iodine solution.
5. Place one edge of a coverslip onto the slide and lower it gently using a mounted
needle, making sure that there are no air bubbles.
6. Gently press the coverslip down using a piece of paper towel.
7. Using the x4 objective position the slide and focus on the section.
8. Swing the x10 objective into place and move the slide carefully until a clear area of
cells are observed i.e. no large bubbles, no folds and a single layer of cells.
9. Draw a group of at least three cells in the correct proportion. Indicate the length of
one cell in eye piece units on the drawing.
10. You should use the x40 objective to help you identify and label structures in the
cells.
11. Calculate the actual size of one of your cells and the magnification of your drawing.

Question 11

3 - Investigation into the permeability of cell membranes using
beetroot

INTRO

Answer 11

INTRO
Heating the membrane can cause gaps to
form between the phospholipid molecules and the membrane will become more permeable.
The protein in the membrane can be denatured by heat

Beetroot cells contain betalain, a bright red, water soluble pigment, in the cell vacuoles. If the
cell membranes are damaged the pigment can escape from the cells and can be detected in
an aqueous medium around the tissue.

Question 12

3 - Investigation into the permeability of cell membranes using
beetroot

APPARATUS

Answer 12

Beetroot cylinders
White tile
10 test tubes
Scalpel
250cm3 beaker
Forceps
Water baths at (25, 35,45,55,65 oC)
Thermometer
Stop clock
Colorimeter with a blue filter / colour chart

Question 13

3 - Investigation into the permeability of cell membranes using
beetroot

METHOD

Answer 13

1. Cut 5 same size beetroot peices eg 1cm (control SA)
2. Wash, remove pigment from cutting
3. Place 1 piece of beetroot into each test tube for 30 minutes, in water bath
4. Shake the test tubes gently to make sure any pigment is well-mixed into the water, then remove the beetroot cores.
5. Colorimeter, set it to respond to a blue/ green filter measure absorbance. Check the colorimeter reading for distilled water.
6. Measure the absorbance/percentage transmission of each tube and plot a graph of absorbance/percentage transmission against temperature.

Question 14

3 - Investigation into the permeability of cell membranes using
beetroot

RISK

Answer 14

Question 15

3 - Investigation into the permeability of cell membranes using
beetroot
THINK ABOUT

Answer 15

Question 16

3- Determination of water potential by measuring changes in mass or length
APPARATUS

Answer 16

Vegetable large enough to extract 50 mm cylinders: potatoes, sweet potatoes, yams,
beetroots, swede, turnip, parsnip and carrot are suitable.
Chopping board/ white tile
Cork borers: sizes 3 and 4 are suitable
Ruler graduated in mm
Fine scalpel
Fine forceps
5 x boiling tubes
Boiling tube rack
50cm3 measuring cylinder
Distilled water
Sodium chloride solutions (0.2, 0.4, 0.6, 0.8 moldm-3 )

Question 17

3- Determination of water potential by measuring changes in mass or length
METHOD

Answer 17

1. Cut 15 cylinders of tissue, each approximately 50mm long, scalpel to remove any periderm (skin) as its suberin makes it waterproof and would prevent osmosis.
2. Place 30cm3 distilled water or solution in to each test tube.
3. Measure the length of the cylinder to the nearest mm or the mass
4. Using the forceps, place 3 cylinders into each boiling tube.
5. Leave at room temperature for a minimum of 45 minutes
6. Gently blot the cylinders and re-measure the length or re-weigh the cylinders.
7. Record your results in a table.
8. Plot the mean percentage change against the concentration of solution.
9. Estimate the solute potential of the tissue.

Question 18

3- Determination of water potential by measuring changes in mass or length
RISK

Answer 18

Question 19

3- Determination of water potential by measuring changes in mass or length
RESULTS

Answer 19

Percentage Change - The calculation is (end mass or length – start mass or length) ÷ start mass or length.

Where the potato tissue has lost mass or length, the answer will be a negative value.

Point at which the water potentials of the tissue and bathing solutions are equal, crosses x axis

The concentration is converted into a solute potential using a standard table. Where the solution and potato tissue have equal water potentials, the solute and water potentials are equal as the cells are in incipient plasmolysis and the pressure potential is 0 kPa.

Question 20

3- determining solute potential by the degree of incipient plasmolysis
INTRO

Answer 20

Question 21

3- determining solute potential by the degree of incipient plasmolysis
APPARATUS

Answer 21

White tile
Fine forceps
Fine scissors
Rhubarb petioles or red onion
5 x 9 cm Petri dishes, 100 cm3 beakers or watch glasses
Distilled water
sodium chloride solutions 0.2, 0.4, 0.6, 0.8 mol dm-3
: instructions for making these
solutions is given in the previous experiment.
Stopclock
Microscope slides
Cover slips
Microscope
Dropping pipettes

Question 22

3- determining solute potential by the degree of incipient plasmolysis
METHOD

Answer 22

1. Set up five labelled Petri dishes/ small bottles each containing 10cm3 of one of the
   following solutions: distilled water, 0.2, 0.4, 0.6, 0.8 moldm-3 sodium chloride solution.
2. Insert the fine forceps tip just under the upper epidermis of the onion leaf.
3. Keeping the forceps handles parallel with the epidermis, so as not to penetrate the
   underlying mesophyll, grip the epidermis and, maintaining the tension in the tissue,
   pull the epidermis off the mesophyll, away from you and place into distilled water.
4. When several square centimetres of epidermis have been peeled, place one square
   into each labelled petri dish/small bottle.
5. Leave at room temperature for a minimum of 30 minutes.
6. Carefully spread the tissue out on a microscope slide, so that it is not folded. Take a
   scalpel and rock the blade backwards and forwards over the tissue in order to cut out
   a 0.5 x 0.5cm square.
7. Add two drops of bathing solution and apply a cover slip.
8. If any solution exudes from the cover slip, blot it with filter paper to dry the slide.
9. Using a x10 and then a x40 objective lens, examine all the cells in a field of view and
   count the number that are turgid and the number plasmolysed.
10. Repeat the counts at all concentrations of bathing solution.
11. Record your results in a table.
12. Plot a graph of % cells plasmolysed against the concentration of the bathing solution.
13. Using the graph, read the concentration of bathing solution that would produce
    plasmolysis in 50% of the cells.
14. From the table given in the previous experiment, determine the solute potential of this
    solution. This is equal to the solute potential of the cells.

Question 23

3- determining solute potential by the degree of incipient plasmolysis
RESULTS

Answer 23

Question 24

3- determining solute potential by the degree of incipient plasmolysis
RISK

Answer 24

Question 25

4 - Investigation into the effect of temperature or pH on enzyme anxiety

Answer 25

Phenolphthalein is an indicator (pink in alkaline solutions of about pH10, colourless in pH conditions less than 8.3) In this investigation, an alkaline solution of milk, lipase and phenolphthalein will change from pink to colourless as the fat in milk is broken down to form fatty acids (and glycerol) thus reducing the pH to below 8.3. The time taken for this reaction to occur is affected by temperature.

Question 26

4 - Investigation into the effect of temperature or pH on enzyme anxiety Apparatus

Answer 26

Apparatus Milk, full-fat or semi-skimmed Phenolphthalein in a dropper bottle lipase solution (5g/ 100cm3 ) Sodium carbonate solution (0.05 moldm–3 ) 5 x Test tubes and rack 2 x 10cm3 syringes/measuring cylinders 2cm3 syringe Stirring rod Thermometer Water baths set to 15oC, 25 oC, 35oC, 45oC and 55oC. Ice

Question 27

4 - Investigation into the effect of temperature or pH on enzyme anxiety Method

Answer 27

1. Place a beaker of lipase solution in the 25 oC water bath. 2. Place 5 cm3 milk, in a test tube. 3. Add 5 drops of phenolphthalein to the test tube. 4. Add 7 cm3 of sodium carbonate solution. 5. Place the test tube in the 25oC water bath for 10 minutes to equilibrate. 6. Add 1 cm3 of lipase from the beaker in the water bath and start the stop clock. 7. Stir the contents of the test tube until the solution loses its pink colour, record the time taken. 8. Repeat steps 1 – 7 for 15oC, 35oC, 45oC and 55oC.

Question 28

4 - Investigation into the effect of enzyme or substrate concentration on enzyme activity

Answer 28

Question 29

4 - Investigation into the effect of enzyme or substrate concentration on enzyme activity Apparatus

Answer 29

Freshly cut potato cylinders Pestle and mortar Specimen tubes/test tubes Stock solution of hydrogen peroxide Filter paper discs Forceps Stopwatch Syringe Distilled water Paper towel

Question 31

4 - Investigation into the effect of enzyme or substrate concentration on enzyme activity Method

Answer 31

1. Grind a 2cm piece of potato cylinder with 5cm3 of distilled water to make a smooth paste containing the enzyme. 2. Place 10cm3 of H2O2 in a specimen tube/ test tube. 3. Using forceps, dip a filter paper disc into the enzyme suspension, tap off the excess. 4. Drop the filter paper disc into the hydrogen peroxide solution and measure the time, to the nearest second, that it takes from striking the surface to sink to float up to the surface again. 5. Remove the disc from the tube using forceps and discard

Question 32

5- Simple extraction of DNA from living material Introduction

Answer 32

DNA can be extracted in visible amounts from a wide source of material such as onions and strawberries. Strawberries are an excellent source because they have very large genomes, and can have up to eight copies of each chromosome (octoploid). Strawberries are soft and, when ripe, they produce pectinase and cellulase enzymes which break down the cell walls helping the release of DNA.

Question 33

5- Simple extraction of DNA from living material Apparatus and reagents

Answer 33

1 resealable plastic bag 1 Strawberry 10cm3 of washing up liquid (detergent) 1g of salt 100cm3 water 2 x 250cm3 beakers (one beaker will be used for the filtering apparatus below) Filtering apparatus: coffee filter paper and beaker Ice cold 90% alcohol 1 ice lolly stick or plastic coffee stirrer Acetic-orcein stain

Question 34

5- Simple extraction of DNA from living material Method

Answer 34

1. Remove the green calyx from the strawberries. 2. Put the strawberry into the plastic bag, seal it and crush it for about two minutes. Make sure that the strawberry is completely crushed. 3. In a beaker, mix together 10cm3 of detergent, 1g of salt and 100cm3 of water. This mixture is the DNA extraction liquid. 4. Add 10cm3 of this extraction liquid to the bag with the strawberry. 5. Reseal the bag and gently mix the extraction liquid with the strawberry for 1 minute. (Avoid making too many soap bubbles). 6. Place the coffee filter inside the beaker. 7. Open the bag and pour the strawberry liquid into the filter. You can twist the filter just above the liquid and gently squeeze the remaining liquid into the beaker. Simple extraction of DNA from living material Specification reference: 1.5 Simple extraction of DNA from living material 48 8. Pour down the side of the beaker an equal amount of cold 90% alcohol as there is strawberry liquid. Do not mix or stir. 9. Within a few seconds, watch for the development of a white cloudy substance (DNA) in the top layer above the strawberry extract layer. 10. Tilt the beaker and pick up the DNA using the plastic coffee stirrer or wooden stick. 11. Test your sample with acetic-orcein stain. A red colour will show that it does contain nucleic acids.

Question 35

6. Scientific drawing of cells from slides of root tip to show stages of mitosis Intro

Answer 35

Introduction Mitosis is a process of cell replication needed for growth and repair. Onion (Allium sp.) is very useful for root tip preparation to study the different stages in mitosis. At the tip of the root there is an apical meristem where cells divide by mitosis. To observe the stages of mitosis the root tissues must be well fragmented. Hydrochloric acid is used to separate the cells by breaking down the tissue which binds cells together (maceration).

Question 36

6. Scientific drawing of cells from slides of root tip to show stages of mitosis Apparatus

Answer 36

Apparatus and reagents Microscope Bunsen burner / hot plate Garlic or onion with developing roots Microscope slide and cover slit Scalpel Fine forceps Watch glass Mounted needle acetic-orcein stain Dropping pipette 1M hydrochloric acid Paper towel

Question 37

6. Scientific drawing of cells from slides of root tip to show stages of mitosis Method

Answer 37

Question 38

2.2 1 - Investigation into biodiversity in a habitat Intro

Answer 38

Biodiversity refers to the number of species (species richness) and the relative number of individuals within each species (species evenness). The type of index and the techniques used to estimate it will depend upon the habitat being studied. The method depends on counting species richness and evenness and substituting the data into a formula to generate a number which is a diversity index. These methods could be used to look at the diversity of invertebrates in a clean and a polluted stream or the ground flora (vegetation) in a woodland compared to a field.

Question 39

2.2 1 - Investigation into biodiversity in a habitat Simpsons Biodiversity Index

Answer 39

Question 40

2.2 1 - Investigation into biodiversity in a habitat Ground Flora - Apparatus

Answer 40

Quadrat/ Identification key for selected species Random number generator or 20 sided dice 2 x 20 Metre tape

Question 41

2.2 1 - Investigation into biodiversity in a habitat Ground Flora - Method

Answer 41

1. Using tape measures set up at pair of axes at right angles to each other in the selected area 2. Generate random numbers/ roll the dice to produce the figures for the x and y co-ordinates to identify the sampling position. 3. Place the quadrat at the generated sampling position. 4. Identify all species present and record the numbers of each present. 5. Repeat for a total of 10 quadrats. 6. Calculate the Simpson's index for the area

Question 42

2.2 1 - Investigation into biodiversity in a habitat Assessing biodiversity of invertebrates - Apparatus

Answer 42

Flat bottomed net Quadrat Identification key for selected species

Question 43

2.2 1 - Investigation into biodiversity in a habitat ​ Assessing biodiversity of invertebrates - Method

Answer 43

1. Use a fixed area sampler or mark an area with a quadrat 2. Place flat edged net held against the stream bottom downstream from the quadrat. 3. Agitate the stream bed with a boot (or use a stick or tool) and ‘kick’ for two minutes, covering the whole area evenly. 4. Place the catch in a shallow white tray with 2 cm depth of fresh water from the stream or river. 5. Identify all species present and record the numbers of each present. 6. Return animals about 1m upstream from where they were caught. 7. Repeat for a total of 10 quadrats (or share results from other groups). 8. Calculate the Simpson's index for the stream.

Question 44

2.3 Investigation into stomatal numbers in leaves 3.Introduction

Answer 44

Stomata are pores surrounded by two guard cells on the aerial parts of plants. They are most densely packed in leaves, which therefore make suitable experimental material. This technique describes how to measure their density in the lower epidermis of a leaf.

Question 45

2.3 Investigation into stomatal numbers in leaves 3.Apparatus

Answer 45

Leaves White tile Fine forceps Fine scissors/scalpel Clear nail varnish/PVA glue Microscope slides Cover slips Dropping pipette Distilled water Microscope

Question 46

2.3 Investigation into stomatal numbers in leaves 3.Method

Answer 46

Question 47

2.3 Investigation into stomatal numbers in leaves 3.Risk assessmen

Answer 47

Question 48

2.3 Scientific drawing of low power plan of a prepared slide of T.S. leaf, including calculation of actual size and magnification of drawing Intro

Question 49

2.3 Scientific drawing of low power plan of a prepared slide of T.S. leaf, including calculation of actual size and magnification of drawing Apparatus

Answer 49

Microscope Slide of TS leaf (dicotyledon)

Question 50

2.3 Scientific drawing of low power plan of a prepared slide of T.S. leaf, including calculation of actual size and magnification of drawing Method

Answer 50

Question 51

2.3 Scientific drawing of low power plan of a prepared slide of T.S. Diagram

Answer 51

Question 52

2.3 Dissection of fish head to show the gas exchange system Intro

Answer 52

A bony fish takes in water at the mouth. When the fish closes its mouth and raises the floor of the buccal cavity, the volume is decreased, and consequently the pressure is increased. Water is then driven over the gills, where gas exchange takes place, and out through the operculum.

Question 53

2.3 Dissection of fish head to show the gas exchange system Apparatus

Answer 53

Large fish head Glass rod Dissecting board Microscope slide Fine scissors Cover slip Large scissors Microscope Fine forceps Water Fine scalpel Gloves

Question 54

2.3 Dissection of fish head to show the gas exchange system Method

Answer 54

Question 55

2.3 Dissection of fish head to show the gas exchange system Risk Assessment

Answer 55

Question 56

2.3 Potometer

Answer 56