7.7.2 Respiratory Structure and Breathing Mechanisms in Humans and Animals (Structured Question 1 & 2)

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Question 1:
Figure I represents a model of the human lungs in the respiratory mechanism.


(a) Based on the model of the lungs in Figure I, what are the equivalent structures to the glass tube and the bell jar in the human respiratory system?
Glass tube: __________
Bell jar: ____________
(2 marks)

(b)(i) The thin rubber sheet represents the diaphragm in the human respiratory system.
What is the function of the thin rubber sheet in the model of the lungs? (1 mark)

(ii) The balloons represent the human lungs.
Explain one characteristic of the balloons which is similar to the human lungs. (2 marks)
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(c)(i) The string in the model of the lungs is pulled down.
Draw the changes to the thin rubber sheet and the balloons in Figure II below. (1 mark)


(ii) Observe your drawing in (c)(i).
Explain the relationship between the changes in the model of the lungs you have drawn and the real human respiratory system. (3 marks)
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(d)(i) The percentage of oxygen and carbon dioxide gases in inspired and expired air is determined by using the J-tube.
Why is the end of the J-tube dipped in potassium hydroxide solution and then followed by potassium pyrogallol solution? (1 mark)

(ii) Table below shows the result of a study on the content of inspired and expired air.


Explain why there is an increase in percentage of carbon dioxide in the expired air. (2 marks)

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Answer:
(a)
Glass tube: Bronchi/ trachea
Bell jar: Rib cage/ ribs

(b)(i)
To control the volume/ pressure of the air in the bell jar

(b)(ii)
Balloons are elastic and can expand and contract

(c)(i)

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(c)(ii)
The diaphragm muscles contract causing the volume of the thoracic cavity to increase. This causes the pressure in the lungs to decrease. Air from the outside is forced in.

(d)(i)
Potassium hydroxide solution absorbs carbon dioxide only whereas potassium pyrogallol solution absorbs both oxygen and carbon dioxide.

(d)(ii)
Carbon dioxide is the product of cellular respiration in the body. Carbon dioxide diffuses out of the cells to be transported to the lungs.


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Question 2:
(a) Sugar is oxidized during respiration.
Explain the process. (4 marks)

(b) After an athlete finished running a race, his breathing is still fast and deep for several minutes. (6 marks)
Explain why.

(c) State the similarities and differences between the human and the grasshopper’s respiratory system based on the structural adaptation to maximize the rate of gaseous exchange. (10 marks)

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Answer:
(a)
- During respiration, oxygen taken in is transported by the blood circulatory system to the body cells.

- In the cells, sugar (glucose molecules) are oxidized by the oxygen to release energy in the form of ATP.

- Other products of this oxidation process are carbon dioxide and water.
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(b)
- He needs to breathe in fast and deep in order to inhale more oxygen.

- This is because during running, the rate of oxygen being used by the muscles exceeds the amount of oxygen supplied by the blood.

- The muscles are in a state of oxygen deficiency.

- An oxygen debt is incurred.

- The muscles obtain the extra energy (ATP) from anaerobic respiration, because oxygen is not available.

- The excess oxygen inhaled is used by the body to oxidise the accumulated lactic acid to carbon dioxide and water.

- When all the lactic acid is removed, the oxygen debt is paid off.
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(c)
Similarities:
- Both respiratory systems have structures which have a large surface area to volume ratio for efficient gaseous exchange.

- The cells that lining the respiratory structures are thin. This allows gas diffusion to take place efficiently.

- The surfaces for gaseous exchange are constantly moist because they are covered by a film of water which allows the respiratory gases to dissolve in it.




5.9.1 Heat Change in Chemical Reactions (Structured Questions)

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Question 1:
Diagram 1.1 and Diagram 1.2 show an experiment to study the heat change in chemical reactions at room temperature.



(a) Based on Diagram 1.1, what is your observation about the change in temperature?
  Mark (\/) for your answer in Table below. [1 mark]


(b) What is the final reading for the thermometer in Diagram 1.2? [1 mark]

(c) State the variables in this experiment.
(i) Constant variable [1 mark]
(ii) Responding variable [1 mark]

(d) State one hypothesis for this experiment. [1 mark]


Answer:
(a)

(b) 35 oC

(c)(i) The amount of water or initial temperature

(c)(ii) The final temperature

(d) In a chemical reaction, heat is given out causing a rise in temperature or is absorbed causing a drop in temperature.


7.7.1 The Respiratory Process in Energy Production (Structured Question 1 & 2)

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Question 1:
Diagram below shows a type of organelle found in muscle cells.
A biochemical reaction occurs in the organelle.


(a)(i) Name this organelle. [1 mark]

(ii) Explain why membrane W is in the form of numerous folded layers. [2 marks]
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(b) The biochemical reaction that occurs in this organelle is summarized as follows:

(i) Name gas R. [1 mark]

(ii) Name product S. [1 mark]

(iii) Explain why the muscle cell has a large number of these organelles. [2 marks]

(iv) If the blood sugar level is lower than the normal range, the biochemical reaction in this organelle can still occur.
Explain how. [3 marks]
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(c) State two differences on the biochemical reaction occurring between muscle cell and yeast cell in the absence of gas R. [2 marks]




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Answer:
(a)(i)
Mitochondrion

(a)(ii)
Membrane W is in the form of numerous folded layers to increase total surface area, for the efficiency of cellular respiration.

(b)(i)
Gas R is oxygen

(b)(ii)
Product S is water

(b)(iii)
Muscle cells need a large number of mitochondrion as an energy ATP supply in order to oxidise glucose in aerobic respiration.
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(b)(iv)
- If the blood sugar is lower than the normal range, less energy is produced.
- Pancreas secretes glucagon to convert glycogen to glucose.
- Cellular respiration occurs.

(c)
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5.5.3 Electrolysis of Molten lead (II) bromide

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5.5.3 Electrolysis of Molten lead (II) bromide

1.   Figure above shows the apparatus set up for electrolysis of molten lead (II) bromide.
2.   Lead (II) bromide powder in a crucible is heated.
3.   The electrolysis process start when le an (II) bromide start melting.
4.   At the Cathode
When electricity is flowing, a silvery deposit of lead metal forms on the cathode.
5.   At the Anode
When electricity is flowing, brown fumes of bromine gas are seen at the anode.
 
Explanation:

 
 
6.   Thus, electrolysis of lead (II) bromide produces lead and bromine gas.
 
 

5.5.2 Electrolysis of Copper (II) Chloride Solution

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5.5.2 Electrolysis of Copper (II) Chloride Solution




1. Electrolysis of copper (II) chloride solution.
(a)  Copper (II) ion with positive charge will attract to cathode to discharge as a copper.
(b)  Chloride ion will attract to anode to discharge as a chlorine gas.
(c)  At anode, chloride ions lose electrons. Greenish gas which can bleach the litmus paper is produced.
(d)  At cathode, copper (II) ion receives electron. Brown solid deposited on the surface of the electrode.
  


2.   Thus, electrolysis of copper (II) chloride produces copper and chlorine gas.
 

5.5 Electrolysis

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5.5 Electrolysis
 
5.5.1 Electrolysis
1. Electrolysis is a process where a compound is separated into its constituent elements when electric current passes through an electrolyte.
 
2. In electrolysis, energy is changed as shown below:
Electrical energy → chemical energy

3. The apparatus used in an electrolytic cell consists of a dry cell or battery, an electrolyte and two electrodes as shown below.


Electrolytic cell


Electrolyte
(a) An electrolyte is a compound in a molten form or in aqueous solution which conducts electric current.
(b) Electrolyte contains two types of charged ions which move freely:
 (i)  Ion with positive charge (cation), for example, metal ions and hydrogen ions.
 (ii) Ion with negative charge (anion), for example, non-metal ions.
(c) Example of electrolyte: molten potassium chloride and hydrocloric acid.
 
Electrode
(a) Electrode is a conductor which is immersed in an electrolyte and connected to an electric source.
(b) Examples of electrode: carbon (graphite) and platinum.
(c) The electrode connected to the positive terminal of the cell is positive electrode and is given a name, anode.
(d) The electrode connected to the negative terminal of the cell is negative electrode and is called the cathode.
 
Ammeter
Ammeter is used to detect the flow of current in the circuit.
 
Dry cell or battery
The source that generates electrical energy.

5.4.2 Reactivity Series and Extraction of Metals

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5.4.2 Reactivity Series and Extraction of Metals

1. The method that is used in the extraction of metal from its are depends on the position of the metal in the reactivity series of metals.
 



2. Metals which are located higher than carbon in the reactivity series are extracted from their molten ores using the electrolysis method.
3. Metals which are located lower than carbon in the reactivity series are extracted using the reduction method with coke (or carbon).
4. Carbon is used in the extraction process because
(a)  It is cheap
(b)  Easily obtained
5. Metals located the lowest in the reactivity series like silver and gold can be extracted naturally without any complex chemical reaction. These metals exist as free elements in the Earth’s crust.

6.16.3 The Mechanism of Photosynthesis (Structured Question 1 & 2)

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Question 1:
Green plants synthesize their food through the process of photosynthesis. The chemical process of photosynthesis can be summarized as in the schematic diagram below.


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(a) State the meaning of photosynthesis based on the schematic diagram. [2 marks]

(b) Starting with water and carbon dioxide as the raw materials, describe how a green plant produces starch molecules. [8 marks]

(c) It is found that the process of photosynthesis contributes to the balance of nature.
Explain how air pollution may have an effect on photosynthesis and the balance of nature. [10 marks]

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Answer:
(a)
A process whereby a green plant produces glucose from carbon dioxide and water in the presence of chlorophyll and sunlight.

(b)
  • Chlorophyll absorbs light energy to produce ATP/ electrons.
  • Photolysis of water produces hydrogen ions and hydroxyl ions.
  • The H+ ions combine with electrons to form hydrogen
  • The hydrogen/ ATP will be used in the dark reaction
  • It occurs in the grana
  • Takes place in the absence of light
  • Carbon dioxide combines with hydrogen to form glucose and water
  • Glucose undergoes condensation and is converted to starch for storage
  • It occurs in a series of chemical reactions which require ATP
  • The reaction occurs in the stroma
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(c)   
  1. The importance of photosynthesis for the balance of nature:
  • Absorbs carbon dioxide from the atmosphere
  • Replaces oxygen in the atmosphere
  • Maintains the percentage of oxygen in the atmosphere
  1. The sources of pollution are motor vehicles and urbanization which will liberate heavy smoke and increase the amount of particles in the air.
  2. The particles accumulate on the leaf surfaces. They cover the stomata and reduce the intensity of the light that reaches the leaves.
  3. As a result, the rate of photosynthesis decreases. Less carbon dioxide is reabsorbed from the atmosphere and less oxygen is released. It also promote the greenhouse effect and global warming.
 
     

    6.16.2 Food Digestion (Structured Question 1 & 2)

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    Question 1:
    (a) Diagram 1.1 shows human digestive system.
    Structure S in Diagram I is involved in the digestion of fat.


    (i)     Name structure S.
    (ii) Name the enzyme which digests fat in S.
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    (iii)     Diagram 1.2 shows a mechanism of an enzyme reaction.
    Draw the diagram in the spaces III and IV provided in Diagram 1.2 to complete the mechanism of the enzyme reaction.


    (b)(i)     Explain how starch is digested in the duodenum.

    (ii)     A student eats too many oranges.
    Explain the effect of eating too many oranges on the digestion of starch in the duodenum.
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    (c)     In a food preparation process, a housewife carries out the following steps:
    Step 1: Marinate pieces of meat with strips of unripe papaya in a basin.
    Step 2: Immerse the basin in a container filled with water at 40oC for 30 minutes as in Diagram 1.3.


    Explain why the housewife carries out Step 1 and Step 2.



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    Answer:
    (a)(i)
    Structure S: Ileum

    (a)(ii)
    Enzyme which digests fat in S is Lipase

    (a)(iii)


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    (b)(i)
    The pancreas secretes an amylase into the duodenum which hydrolyses starch to maltose.

    (b)(ii)
    - The duodenum medium becomes acidic
    - Which is not suitable for the action of the amylase on starch
    - Slows down the digestion of starch

    (c)
    - Papaya contains papain/ protease
    - The pieces of meat and papaya strips increase the total surface area
    - To increase enzyme action
    - Protease will tenderize the meat
    - Takes place in water at 40oC, which is the optimum temperature for enzyme reaction

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    6.16.1 Malnutrition (Structured Question 1 & 2)

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    Question 1:
    (a)(i) After absorption of nutrients in the small intestine, the undigested substances in the colon result in the formation of faeces.
    Explain the formation of faeces in a human. [4 marks]

    (ii)     Malnutrition is a condition due to taking an unbalanced diet in which certain nutrients are lacking, in excess or in the wrong proportions.
    Explain the effect on a child who is given insufficient amounts of any two nutrients of food for a long period of time. [6 marks]
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    (b)     Table below shows the food intake by a boy aged 15 years in his daily menu. The daily energy requirement for him is 12500 kJ.


    (i)     Based on the Table, state the value of energy contained in this daily food intake.
    Does the food intake satisfy his daily energy requirement? [2 marks]

    (ii)     This boy takes this menu continuously for a long time. [8 marks]

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    Answer:

    (a)(i)

    • The contents in the small intestine that are not absorbed enter the colon.
    • The intestinal content consists of a mixture of water, indigestible food, bacteria, dead cells and pigments.
    • The contents move slowly along the colon by peristalsis.
    • Water is reabsorbed and faeces are formed.

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     (ii)
    • A child who is deficient in protein may suffer from kwashiorkor.
    • Protein is needed for normal growth. Lack of protein causes growth of the child to be stunted.
    • A child who is deficient in vitamin C may suffer from scurvy.
    • Vitamin C is needed for healthy gums and skin. Lack of vitamin C causes swollen and bleeding gums.
    • A child who is deficient in roughage may suffer from constipation.
    • Roughage is needed to stimulate peristalsis.
    • Lack of roughage causes difficulty in defaecation.
     (b)(i)
    Total energy = 8230 kJ
    The energy produced from the food taken daily is insufficient.
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    (b)(ii)