DO NOT Write in This Booklet

STANDARD GRADE BIOLOGY

HOMEWORK

INSTRUCTIONS

DO NOT write in this booklet

Where asked to complete sentences, tables etc,

COPY the item into your jotter first.

Title each homework and make sure that each answer is correctly numbered.

Line graphs should ALWAYS be done on graph paper.

HOMEWORK 1INVESTIGATING LIVING CELLS

The diagrams below show three different cells, not drawn to scale.

a)Select information from the diagrams above to complete the table below.

The information on the onion cell has been completed for you.

Tick = presentcross = absent

PS 2

Part of cell / Human cheek cell / Onion cell / Leaf cell
Nucleus
Cell membrane
Cell wall
chloroplast

b)Name two features which are found only in plant cells.

______

KU 2

c)Describe how cells can be treated so that the cell contents become more visible.

______

KU 1

d)Cells increase in number by cell division.

Name the part of the cell that controls cell division.

______

KU 1

a) A pupil was asked to describe the cells she was looking at with a microscope.

The girl said.

“Well, the material looks like a brick wall.

All of the bricks have a small circle in them.

I can just see a very thin line making an odd shape inside each brick.

It looks like each brick has a half empty plastic bag in it”.

Is the pupil looking at animal cells or plant cells?

From your knowledge of cells, give two reasons for your answer.

Cell type______

Reason 1______

Reason 2______

KU 2

b)The diagram below shows the single-celled organism Euglena.

Which structure shown in the diagram would suggest that this is a plant?

______

KU 1

c)The diagram below shows some human cheek cells as they appear when viewed through a microscope.

The diameter of the field of view of the microscope is 120 micrometers.

Calculate the average width of a human cheek cell.

Space for calculation

Average width = ______micrometers.

PS 1

a) Beetroot is red because its cells contain red pigment. When the cell membranes are damaged, this pigment can leak out. In an experiment to investigate the composition of cell membranes, four test tubes were set up as shown, and left for one hour.

The results are shown in the following table.

Tube / 1 / 2 / 3 / 4
Colour of liquid in tube after 1 hour / clear / red / red / red

i)State the effect of temperature on the membrane.

______

PS 1

______

ii)What two conclusions can be drawn about the composition of cell membrane from the results?

______

PS 2

Carefully read the following passage.

Adapted from ‘Life in a Plant Cell Wall’ by Stephen Fry.

(Biological Sciences Review 4.1)

The living part of every plant cell is neatly packaged within a plant cell wall. The chief chemical substance of a plant cell wall is cellulose. However, plant cell walls are not made up of cellulose alone. Plants have developed cell walls which are complicated. The cell walls of a growing plant are built up from at least six different sugars; at least two structural proteins; about twenty different enzymes and small quantities of many other substances. Cell walls are complex structures and this complexity must be important to plant life. Cell walls, therefore, must not be seen simply as “cardboard boxes”.

Cell walls can be removed from plant cells by treating the cells with appropriate digestive enzymes in sugar solution. The resulting cells, now without their walls, can remain alive for several days and are called “protoplasts”. They differ from the original cells in several ways, including:

neighbourliness – they are freely floating independent cells instead of being organised together in tissue;
size – they have no fixed volume. When put into pure water, they swell and burst. Normal plant cells cannot swell beyond a certain size when placed in pure water.

The diagrams below show the structure of a normal leaf cell and a protoplast.

Answer the following questions which relate to the passage.

a)Identify three components of a plant cell wall.

______

______PS 1

b)State the function of the digestive enzymes (line 9).

______

PS 1

c)What is a protoplast? (line 10).

______

PS 1

d)Name two cell structures, present in a protoplast, which are also present in animal cells.

______

KU 2

e)What is meant by the term neighbourliness in the passage (line 12)?

______

PS 1

f)The passage describes differences between a protoplast and a normal plant cell.

Select from the diagrams, one other difference between them.

Difference ______

______

PS 1

Total:20 marks

HOMEWORK 2INVESTIGATING DIFFUSION

a) Substances enter and leave cells by diffusion.

i)Give one example of each type of substance.

Enters cell ______Leaves cell ______KU 1

ii)Which structure controls the passage of some substances into and out of the cell?

______KU 1

iii)Explain the importance to cells of diffusion.

______

______KU 1

a) State the meaning of the term “osmosis”.

______

______KU 1

b)Below is a list of statements which may be used to explain examples of osmosis in action.

AConcentration of water inside cell(s) is greater than outside.

BConcentration of water outside cell(s) is greater than inside.

CConcentration of water inside cell(s) is the same as that outside.

DWater enters the cell(s).

EWater leaves the cell(s).

FThere is no net movement of water.

For each of the following examples, select the letters of the two statements which together provide a correct explanation.

Examples / Letters
Red blood cells swell and burst when placed in pure water.
The mass of potato tissue decreases when place in 10% sucrose solution.

KU 2

c)An experiment was set up as shown in the diagram below.

Explain how the process of osmosis causes the changes at X an Y.

______

______KU 2

a) Five cylinders of fresh potato were blotted dry and their mass was recorded. Each one weighed 5g. One cylinder was placed in each of five test tubes as shown below. After 24 hours they were again dried and weighed. The cylinder in tube A now weighed 4g, and that in tube E weighed 4.5g.

i)What processes might cause a change in mass in tube A and in tube E?

Tube A______

Tube E______KU 2

ii)Which of the 5 cylinders is likely to be heaviest at the end of the experiment?

______PS 1

iii)What is the percentage fall in mass recorded for the cylinder in tube A?

______PS 1

a) A piece of potato was cut into six equal sized strips.

The lengths were measured and the strips placed into sugar solutions of different concentrations.

After two hours, the lengths were re-measured.

The results are shown in the table below.

Solution / Initial length
/mm / Final length
/mm / Change in length
/mm
A
B
C
D
E
F / 50
50
50
50
50
50 / 42
44
47
51
52
56 / -8
-6
-3
+1
+2
+6

i)Explain, in terms of difference of water concentration, the change in length which occurred to the strip in solution F.

______

______KU 1

ii)Which solution has water concentration closest to that of the potato cells?

Letter ______PS 1

iii)Use the results for change in lengths of the potato strips to construct a bar chart.

Increase

Change in length

/mm

Decrease

PS 2

A group of pupils was asked to investigate the effect of osmosis on the diameter of discs of potato tissue.

The procedure followed is outlined below.

i)A large diameter cork borer was used to cut a cylinder of tissue from a peeled potato.

ii)Five discs, each 2mm thick, were cut from the cylinder.

iii)Four discs were transferred to separate Petri dishes.

iv)The diameter of each disc was measured from graph paper placed underneath the dish.

v)20 cm3 of glucose solution, of different concentrations, was poured into each of three dishes. 20 cm3 of water was poured into a fourth dish.

vi)The apparatus was left for 30 minutes and the diameter of each disc was remeasured.

Diagram 1 below shows the apparatus and Diagram 2 shows how the diameter of a disc was measured.

Solution / Concentration of glucose solution / Diameter of disc (mm)
At start / After 30 minutes
A / 0.0% / 14.0 / 16.2
B / 0.5% / 14.0 / 15.4
C / 1.0% / 14.0 / 14.0
D / 1.5% / 14.0 / 12.6

a)Identify the variable which was altered and two variables which were kept constant in the investigation.

Altered variable______

Variables kept constant______

______

PS 1

b)Identify the solution which has a water concentration higher than that present in the potato tissue.

Solution______

PS 1

c)The fifth disc, of initial diameter 14.0 mm, was placed in a solution of unknown glucose concentration.

The diagram below shows the size of the disc after 30 minutes.

(i)Calculate the change in diameter of this disc.

Space for calculation

Change in diameter ______mm.

PS1

(ii)The concentration of the unknown glucose solution lies within one of the following concentration ranges.

Tick the correct box

0% - 0.5%
0.5% - 1.0%
1.0% - 1.5%

PS 1

Total :20 marks

HOMEWORK 3INVESTIGATING CELL DIVISION

a) A cell can divide to produce two daughter cells.

Each daughter cell grows and then divides.

The beginning of these divisions is shown in the diagram below.

(i)Calculate the number of cells in the 4th generation.

Answer: ______cells

PS 1

(ii)The nucleus of the cells formed in the 4th generation contains 16 chromosomes.

How many were present in the original cell?

______KU 1

b)The following statements refer to main stages in mitosis.

The diagrams show two stages in this process.

For each diagram, select a statement which matches it. Write the appropriate letter below the diagram.

Statements

AChromosomes gather at the equator of the cell.

BNuclear membrane breaks down.

CChromosomes become visible in the nucleus.

DNuclear membrane forms round chromosomes at poles.

Diagrams

Letter ______Letter ______

KU 2

a) The following diagrams show cells at different stages of mitosis.

Which sequence shows the correct order of the stages?

U  V  W  Y  X
U  W  X  Y  V
U  V  Y  W  X
U  V  X  W  Y

KU 1

b)The table below refers to cell division and mitosis in a multicellular organism.

Tick one statement in each column to identify correctly features of cell division.

Function of cell division / Control of cell division / Number of chromosomes in each cell
Increases the number of cells in an organism / Cytoplasm / Twice as many as in the parent cell
Increases the size of each cell / Nucleus / Same number as in the parent cell
Allows the organism to reproduce / Cell membrane / Half as many as in the parent cell

KU 3

c)Which of the following sentences about mitosis are correct?

Mitosis is necessary for growth in organism.
Mitosis reduces the number of chromosomes in the newly produced cells.
Mitosis occurs in both plant and animal cells.
Mitosis produces identical daughter cells.

Tick the correct box

A. / 1,2,3 and 4 are correct
B. / 1,2 and 3 only correct
C. / 1,3 and 4 only correct
D. / 2 and 3 only correct
E. / 1 and 4 only correct

3. The following diagram shows a cell undergoing mitosis.

a)Name the parts labelled A and B.

A______

B______KU 2

b)The Letter C labels the spindle. Describe the function of the spindle during mitosis.

______

______PS 1

4. The graph below shows changes in the number of yeast cells growing in a liquid culture medium kept at 30C for 24 hours.

i)During which four hour period was there the greatest increase in the number of yeast cells?

Tick the correct box

4 – 8 hours
8 – 12 hours
12 – 16 hours
16 – 20 hours
20 – 24 hours

PS 1

ii)State the number of hours it takes for the number of yeast cells to stop increasing and become constant.

______hours

PS 1

iii)At eight hours there are 200 million yeast cells/cm3.

How long does it take for there to be double this number?

______hours

PS 1

Total: 15 marks

HOMEWORK 4INVESTIGATING ENZYMES

Which two of the following statements explain why a cell contains a wide variety of different enzymes?

All chemical reactions in living cells are controlled by enzymes.
Different enzymes have different optimum conditions.
Each enzyme reacts with a specific substrate.
Enzymes are unchanged at the end of a chemical reaction.

Write the two letters in the boxes below:

a) The two graphs refer to the activity of an enzyme.

State the temperature and the pH at which the activity of this enzyme is greatest.

Temperature:______PS 1

pH:______PS 1

b) The graph below refers to the activity of two enzymes.

i)Describe the effects of change in pH on enzyme activity.

______

______PS 2

ii)Which graph would be representative of the action of the enzyme pepsin?

Graph______KU 1

Separate test tubes containing starch suspension and amylase solution were placed in water-baths set at a range of temperatures.

When the required temperatures were reached, the amylase was added to the starch. The mixtures were left in the water-baths at these temperatures for 30 minutes.

Samples were then analysed for the quantity of sugar present.

The results are shown in the table below.

Temperature/C / 0 / 15 / 30 / 40 / 50 / 70
Units of sugar / 5 / 30 / 60 / 80 / 10 / 0

a)From the results, state the optimum temperature for this enzyme.

Temperature:______KU 1

b)Amylase is specific to the substrate starch.

Explain the meaning of the term “specific”.

______

______KU 1

c)What would be the effect on the results at 70C, if the starch suspension and amylase solution had been mixed before being placed in the water-bath?

Explain the answer.

Effect: ______

______

Explanation______

______

______PS 2

4. a) The enzyme catalase is found in living cells.

It can break down hydrogen peroxide forming oxygen.

In each of the following experiments a 1cm3 cube of liver was used.

The results are shown in the table below the diagram.

Tube / A / B / C
Result / some oxygen bubbles appear / no oxygen bubbles appear / many oxygen bubbles appear

i)In terms of enzyme activity, give a possible reason for the difference in results between:

Tube A and tube B;

______

______PS 1

Tube A and tube C.

______

______PS 1

ii)When the experiment was repeated using a 1cm3 cube of fresh potato, the reaction was much slower than with fresh liver.

What conclusion can be drawn from this?

______

______PS 1

b) The apparatus was set up as shown in the diagram below.

The cubes of plant tissue were of equal size.

Each measuring cylinder contained 10cm3 of hydrogen peroxide solution.

The depth of the froth was used as a measure of the volume of oxygen produced.

i)Describe a suitable control for this investigation.

______

______PS 1

ii)Catalase activity is greater in potato than in apple or carrot.

Select two features of the experimental set up which allow this conclusion to be drawn.

Feature 1______

______

Feature 2______

______PS 1

The enzyme trypsin will dissolve egg white at different rates depending on the pH. The following table indicates the time taken by trypsin to clear a cloudy suspension of egg white at different pH values.

pH / Time taken for egg white suspension to become clear/hours
6
7
8
9
10 / 6
4
1
3
4

Which of these graphs best represents these results? Tick the correct box.PS 1

Rennin is an enzyme from the stomach of young mammals. The enzyme clots milk, changing it from a liquid to a solid. As it thickens, the milk flows more slowly.

The rate of thickening of fresh milk by rennin was investigated. A rennin tablet was crushed to powder and mixed with 150 cm3 of fresh milk. Ten syringes were set up, each containing 10 cm3 of the mixture.

The plunger was removed from one syringe barrel immediately and the time taken for this syringe to empty was recorded. The plungers were removed from the other syringes at 10 minute intervals and the time taken for each syringe to empty was also recorded.

The graph below records the results of the investigation.

i)How long did it take for the syringe to empty, starting 50 minutes after the rennin had been added to the milk?

Answer: ______PS 1

ii)Using information from the graph, describe the effect of rennin on milk.

______

______PS 2

iii)Describe a suitable control for this experiment.

______

PS 1

Total: 20 marks

HOMEWORK 5INVESTIGATING AEROBIC RESPIRATION

1.a)

i) Complete the word equation below for the process which uses oxygen to release energy in cells.

______+ oxygen  water + ______+ energy

KU 2

iii)What is the name of this process?

______KU 1

a) Energy from respiration can be used in a variety of ways. Use lines to connect up the use of energy with an appropriate example of this use. The first is done for you.

Use of energy
Heating
Mechanical work
Chemical work
Electro-chemical work
Transport / Example
Muscle
Nerve action
Blood heated by liver
Digestion
Circulation

b) A pupil used the apparatus shown below to investigate the energy content of two different foods.

State two ways in which the experiment could be improved to produce valid results.

Firstly:______

Secondly:______

KU 2

A pupil set up the apparatus shown below to investigate the effect of temperature on the rate of oxygen uptake by an earthworm.

An earthworm was placed in one test tube and glass beads equal in volume to the worm were placed in the other.

The test tubes of the apparatus were place in a water bath set at 5C and left for 10 minutes with the taps open to the air.

The taps were then closed and the apparatus left for 1 hour. The volume of oxygen taken up was then measured.

The procedure was repeated over a range of temperatures. The results are shown in the table.

Further information

The syringe is used to return the coloured liquid to the original levels in both arms of the U-tube.

a)Explain why the glass beads are included in the experiment.

______

______PS 1

b)Without altering the apparatus, how could the reliability of the results be improved at each temperature?

______

______PS 1

c)On the grid below, plot a suitable line graph to show the effect of increasing temperature on the rate of oxygen uptake.

PS 2

d)From the results, describe the relationship between temperature and oxygen uptake in earthworms.

______

PS 2

The apparatus drawn below was set up to demonstrate aerobic respiration.

After a few days, it was found that the level of the water had risen in the tube on Side B.

a)Explain why small changes in room temperature during the experiment can be ignored.

______

______PS 1

b) Name two factors which must be kept constant in the experiment.