Questions
Instructions to candidates
- You are required to spend the first 15 minutes of the 13/4 hours allowed for this paper reading the whole paper carefully before commencing your work.
- You are provided with small pieces of two tissues, labeled P and Q, obtained from an animal.
- Cut each specimen into two equal halves. From each specimen, crush one half and leave the other half as a solid piece. Place the solid half of specimen P into a test tube labeled K. Place the solid half of specimen Q into a test tube labeled L.
Put about 2cm3 hydrogen peroxide into each of the test tubes.- State the observations made in the two test tubes. [2marks]
Test tube K
Test tube L - Place the crushed specimen P into test tube labeled M and also place the crushed specimen Q into test tube labeled N. Add 2cm3 hydrogen peroxide into test tube M and N. Record the observation for each test tubes M and N in comparison to K and L [2marks]
Test tube M
Test tube N - Write down an equation for the reaction that was responsible for your observations in the experiments above. [1mark]
- Name the process represented by the equation in (iii) above. [1mark]
- State the observations made in the two test tubes. [2marks]
- Explain how crushing affected the results of the experiments. [2marks]
- Apart from the process named in (a) (iv) above, name three other functions of specimen Q [3marks]
- Explain the importance of the process named in (a) (iv) above in living organisms [3marks]
- Cut each specimen into two equal halves. From each specimen, crush one half and leave the other half as a solid piece. Place the solid half of specimen P into a test tube labeled K. Place the solid half of specimen Q into a test tube labeled L.
- You are provided with specimen labelled Z which has been grounded into flour.
Make a solution of the flour provided by adding water and stirring properly. Sieve or decant to obtain a solution from the mixture.-
- Using the reagents provided test for the presence of starch, proteins and lipids in the solution from specimen Z. Record the procedures, observation, and conclusions in the table below. [9marks]
FOOD SUBSTANCES PROCEDURE OBSERVATION CONCLUSION Starch
Proteins Lipids - From the conclusions made in (a) (i) above, suggest the regions of the alimentary canal where the digestion of specimen Z would take place. [3marks]
- Using the reagents provided test for the presence of starch, proteins and lipids in the solution from specimen Z. Record the procedures, observation, and conclusions in the table below. [9marks]
- State one use of any two food substances found in specimen Z. [2 marks]
-
- You are provided with leaves of specimens A, B, C, D, and E.
- Use the following features in the order in which they are listed, to prepare a dichotomous key: [8 marks]
Type of leaf
Shape of the lamina
Succulent or non-succulent
Leaf margin -
- Name the likely habitat of specimen C. [1mark]
- Give a reason for your answer in (b) (i) above. [1mark]
- State the significance of the shiny upper surface of specimen A. [2marks]
- Use the following features in the order in which they are listed, to prepare a dichotomous key: [8 marks]
Confidential
- Piece of flesh labeled P
- Piece of Liver labeled Q
- Groundnuts flour labelled Z( each student requires about 20gms of the flour)
- Leaves –
- Broad leave with smooth margins e.g Mango labeled A
- Grass leaf Labeled B.
- Tradescantia leaf / any succulent leaf labeled C
- Broad leaf with serrated leaf margin e.g Tobacco leaf labeled D
- Compound leaf e.g Jacaranda labeled E.
- Iodine solution
- Absolute ethanol
- 10% sodium hydroxide solution
- 1% copper (ii) sulphate solution
- Hot water bath
- Means of labeling
- Four test tubes
Marking Scheme
- You are provided with small pieces of two tissues, labeled P and Q, obtained from an animal.
- Cut each specimen into two equal halves. From each specimen, crush one half and leave the other half as a solid piece. Place the solid half of specimen P into a test tube labeled K. Place the solid half of specimen Q into a test tube labeled L.
Put about 2cm3 hydrogen peroxide into each of the test tubes.- State the observations made in the two test tubes. [2marks]
- Test tube K …………less effervescence
- Test tube L …………more effervescence compared to K
- Place the crushed specimen P into test tube labeled M and also place the crushed specimen Q into test tube labeled N. Add 2cm3 hydrogen peroxide into test tube M and N. Record the observation for each test tubes M and N in comparison to K and L [2marks]
- Test tube M ………more effervescence compared to K
- Test tube N ………more effervescence compared to L
- Write down an equation for the reaction that was responsible for your observations in the experiments above. [1mark]
- Hydrogen peroxide → water + oxygen gas
- Name the process represented by the equation in (iii) above. [1mark]
- detoxification
- State the observations made in the two test tubes. [2marks]
- Explain how crushing affected the results of the experiments. [2marks]
- Crushing increased the surface area ;upon which enzyme catalase can speed up the decomposition of toxic hydrogen peroxide ;
- Apart from the process named in (a) (iv) above, name three other functions of specimen Q [3marks]
- Deamination
- Blood sugar regulation
- Thermoregulation
- Regulation of plasma proteins
- Haemoglobin regulation
- Explain the importance of the process named in (a) (iv) above in living organisms [3marks]
- Harmful/ toxic substances e.g hydrogen peroxide are broken down; to less harmful substances such as water and oxygen gas; this creates a conducive environment for physiological processes in the cell;the oxygen gas produced can also be used in respiration;
- Harmful/ toxic substances e.g hydrogen peroxide are broken down; to less harmful substances such as water and oxygen gas; this creates a conducive environment for physiological processes in the cell;the oxygen gas produced can also be used in respiration;
- Cut each specimen into two equal halves. From each specimen, crush one half and leave the other half as a solid piece. Place the solid half of specimen P into a test tube labeled K. Place the solid half of specimen Q into a test tube labeled L.
- You are provided with specimen labelled Z which has been grounded into flour.
Make a solution of the flour provided by adding water and stirring properly. Sieve or decant to obtain a solution from the mixture.-
- Using the reagents provided test for the presence of starch, proteins and lipids in the solution from specimen Z. Record the procedures, observation, and conclusions in the table below. [9marks]
FOOD SUBSTANCES PROCEDURE OBSERVATION CONCLUSION Starch To 2ml of solution Z,add iodine solution dropwise; Blue-black colour is observed Starch present; Proteins To 2ml of solution Z,add equal amount of 10% sodiumhydroxide solution followed by 1% copper (ii) sulphate solution; Purple/violet colour is observed ; Proteins present; Lipids
To 2ml of solution Z,add 4ml of absolute ethanol and shake .transfer into another test tube half filled with water;Formation of white emulsion ; Lipids present; - From the conclusions made in (a) (i) above, suggest the regions of the alimentary canal where the digestion of specimen Z would take place. [3marks]
- Starch –mouth;duodenum;
- Proteins –stomach;duodenum;
- Lipids –duodenum;ileum;
- Using the reagents provided test for the presence of starch, proteins and lipids in the solution from specimen Z. Record the procedures, observation, and conclusions in the table below. [9marks]
- State one use of any two food substances found in specimen Z. [2 marks]
- Starch –digested to glucose which is then oxidized during respiration to generate energy;
- Proteins –digested to amino acids which are then oxidized to release energy during starvation;
-
- You are provided with leaves of specimens A, B, C, D, and E.
- Use the following features in the order in which they are listed, to prepare a dichotomous key: [8 marks]
- Type of leaf
- Shape of the lamina
- Succulent or non-succulent
- Leaf margin
- 1 a) leaf simple………………………………………………………….go to 2 b) leaf compound………………………………………………………E
- 2 a) leaf with broad lamina ……………………………………………go to 3
b) leaf with narrow lamina……………………………………………B - 3 a) leaf succulent ……………………………………………………… C
b) leaf non-succulent……………………………………………………go to 4 - 4 a) leaf with serrated margin ……………………………………………..D
b) leaf with smooth margin……………………………………………….A
-
- Name the likely habitat of specimen C. [1mark]
- Desert;
- Give a reason for your answer in (b) (i) above. [1mark]
- Succulent leaves to store water
- Name the likely habitat of specimen C. [1mark]
- State the significance of the shiny upper surface of specimen A. [2marks]
- Shiny to reflect light away; hence reduce the rate of transpiration;
- Use the following features in the order in which they are listed, to prepare a dichotomous key: [8 marks]
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