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ANSWERS TO BIOLOGY TOPICAL QUESTIONS – Gaseous exchange in (a) plants  (b animals


1.         (a) Gaseous exchange is the movement of gases across a respiratory surface; while           

      respiration is the biochemical breakdown of food molecules to produce energy (and carbon

      IV oxide);

            (b) Ethanol/Alcohol;

                Carbon (IV) oxide; and energy;      (any two )       

2.         (a)  Glycosis;                                                                                                                          

       Krebs cycle;

(b) Krebs cycle; became oxygen is used to oxidize acid to water, Carbon (IV) Oxide and energy;

3.         a) anaerobic respiration/fermentation;                                                                                   

            b) -baking of bread

             -brewing industry

4.         Carbon (IV) oxide produced in respiration is utilized in photosynthesis; oxygen produced

            in photosynthesis is used in respiration;       

5.         a) Amount of oxygen required to get rid of lactic acid that accumulates in the body tissues when

                oxygen available is lower than the demand                                                                         

            b) Energy/A.T.P/ Lactic acid 

6.         (a) Germinating seeds respired using oxygen in the conical flask and produced CO2, which was absorbed  by the sodium hydroxide solution. A partial vacuum was created in the conical flask. The atmospheric pressure being higher pushes the water down to A and upto B.                       

(b) RQ – Vol of CO2 produced = 102 = 0.70;

                   Vol. of O2 used          145

(c) Lipids;

7.         (a)

– Complete oxidation of lipids require a lot of oxygen;

– Lipids are insoluble in water hence difficult to transport in the body

– Complete oxidation of lipids take a longer time     

(b) Maltose


8.         a)  i)  Cytoplasm                                                                                                                    

              ii) Pyruvic acid

         b) Pyruvic acid is broken down; into ethanol and CO2

9.         a) RQ = CO2 produced                                                                                                          

                          O2 consumed

                                    = 5       ;           = 0.83;


            b) Protein;

10.       Bacteria, bacteria/       Symptoms

            – Prolonged coughing and vomiting

            – Convulsions and coma

            – Conjuctival haemorrhage

            – Severe bronchopneumonia

            Causative agents


11.       – Lowers saturation deficit by trapping H2O moisture;                                                         

            – Protects direct sunlight to the stomatal pore;

12.       They form depressions such that when wind blows it does not carry away water molecules.

13.       – Increase rate of respiration                                                                                                  

            – Speeds up the heart beat rate

14.       A  rat has  a large surface  area  to  volume ratio thus  loses a lot  of  energy   on form of  heat therefore  eats a lot  to replace  the  lost energy;                                                       

15.       a)Glucose                          water + carbon(iv) oxide + energy/210kj                        


C6H12O6                           H2O + CO2 + ATP (energy) (mark as a whole) 1mk

16.       Insoluble hence not easily transported to respiratory sites;                                                   

             – They require more oxygen to be oxidized;

17.       – Making of beer/Brewing/Ethanol/alcohol;                                                               

           – Baking industry/Raising of the dough:

18.       (a) Respiration – Chemical breakdown of food to release energy.                                        p

                 Respiratory surface – Surface across which respiratory gases exchange.                        

            (b) Circulatory system transports the respiratory gases to and from tissues; hence maintains

                 steep concentration gradient around the respiratory surface;

19.       – Not every soluble/not readily soluble therefore not easily transported to the site of respiration;

            – A lot of oxygen is required to oxidize one gram of fat/liquid than one gram of glucose;

20.       a) RQ = Volume of CO2 given out = 102 = 0.70;

                          Volume of O2 used;             145                                                                              

            b) Fats/ oil/ lipid;                                                                                                                   

            Reason: RQ for lipids/ fats/ oils is always less than 0.8; more oxygen is used than

                           carbon  IV produced;          

21.       (a) Boiling

            (b) becomes  milky/cloody /precipitate.

(c) Yeast produces enzyme amylase which catalyze  breakdown of glucose anerosiccally into

     energy (heat)

CO2 and Ethanol

CO2 makes lime water to become cloudy                                                                              

            (d) High temperature donators enzymes, reduces/stops respiration/stops the reaction.

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