SPM Biology 2018


6) Diagram 6.1 shows a gaseous exchange in the alveolus.

Rajah 6.1 menunjukkan pertukaran gas dalam alveolus.

(a) Explain how oxygen is transported to the body tissues for cellular respiration.

Terangkan bagaimana oksigen diangkut ke tisu badan untuk respirasi sel.(b) Based on the statement above, suggest and explain how to keep our lungs healthy.

Berdaarakan pernyataan di atas, cadang dan terangkan bagaimana kita dapat memelihara kesihatan peparu.

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(c) Diagram 6.2.1 and 6.2.2 show the respiratory organ from two different organisms. Explain similarities and differences in structures of the respiratory organ between the two organisms.

Rajah 6.2.1 dan Rajah 6.2.2 menunjukkan organ respirasi bagi dua organisma yang berbeza. Terangkan persamaan dan perbezaan struktur organ respirasi antara dua organisma itu.

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Answer ( 1 )


    6. a)  The concentration and partial pressure of oxygen is higher in the alveolus compared to the blood capillaries surrounding the alveolus. Oxygen can then diffuse from the alveolus into the blood capillaries and combines with haemoglobin to form oxyhaemoglobin. This blood then leaves the alveolus and now contains a higher partial pressure of oxygen compared to the body tissues. The body tissues undergo cellular respiration which decreases the concentration of oxygen of the cells. Thus, oxyhaemoglobin then breaks down to release oxygen which can then diffuse across the blood capillaries to the body tissues. This oxygen can then be used for cellular respiration. 

    note: it is important to compare the partial pressures of oxygen and state where oxygen diffuses from and to


    b) To keep our lungs healthy, it is important to avoid smoking. Smoking causes heat to be released and this heat increases the temperature of the lungs which results in damage to the epithelial tissue in the alveoli and respiratory tract. Furthermore, cigarette smoke contains harmful subtances like carbon monoxide, tar and nicotine. Carbon monoxide is dangerous as it competes with oxygen for binding with haemoglobin. This can form carboxyhaemoglobin which is a very stable compound and it causes less oxygen to be transported to the body tissues. Tar can cause lung cancer and it blackens the lungs. Moreover, nicotine restricts the beating movement of the cilia of epithelial cells. So it is very important to avoid smoking to keep our lungs healthy.

    Another way to keep our lungs healthy is to avoid construction places or industrial factories which release dust, soot or harmful pollutants into the air. These can be irritating to the lungs, so it is best to wear masks with air filters if there is need to be around these areas or during a haze. 



    Human Fish
    Have lungs for respiratory organs. Respires via nostrils.  Have gills for respiratory organs. Respires using mouth and operculum.
    Have many alveoli (air sacs) which provides a large surface area for efficient gas exchange. 


    Have a large number of gill filaments and lamellae which creates a large surface area for efficient gas exchange. 
    Alveoli are thin-walled, only one-cell thick  to allow efficient diffusion of gases across the membranes. Gill filaments membranes are very thin so that there is efficient exchange of respiratory gases into and out of the blood capillaries.
    Each alveolus is covered with a dense network of blood capillaries which creates a large surface area to volume ratio, this allows respiratory gases to rapidly diffuse and be transported quickly .  Gill filaments have a network of blood capillaries which provides a large surface area to volume ratio, this allows for rapid exchange and transport of respiratory gases. 
    Each alveolus has an inner epithelial lining which provides a moist surface for gases to dissolve.  Gill filaments are surrounded by water which allows for gases to dissolve in it.

    10 marks, so you would only need to write five points for each organism. 

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