BIOLOGY TOPICAL QUESTIONS AND ANSWERS-Cell Physiology – Osmosis, Diffusion and Active transport


1.         Two equal strips A and B were from a potato whose cell was 30% of sugar. The strip A was placed in a solution of 10% sugar concentration while B was placed in 50% sugar concentration

           a) What change was expected in strip A and B                                                                     

      b) Account for the change in strip A                                                                                     

2.         An experiment was set-up as shown below and left for one hour

(a) State the expected result at the end of one hour                                                                            (b) b. b. Explain the observations made in this experiment

3.         State what would happen in each of the following:-                                                             

            (a) A plant cell placed in: –        (i) Strong salt solution                                

                                                               (ii) Distilled water  

4.         State three physiological processes that are involved in movement of      substances a cross the cell membrane 

5.         Potato cylinders were weighed and kept in distilled water evernight. They  were then       


                        2.5 g   2.4g    2.7g                                           3.0 g          3.1 g              3.2g            

At the beginning of the Experiment.                 At the end of the experiment

a) Calculate the average mass of a potato cylinders after reweighing. Show your working.

b) Explain why mass of the cylinders hand increased.                                                          

6.         The diagrams below show a red blood cell that was subjected to a certain treatment.    


           a) Account for the shape of the cell at the end of the experiment.

           b) Draw a diagram to illustrate how a plant cell would appear if subjected to the same treatment

7.         The diagram below shows the results obtained when red blood cells are placed in different

(a) What name is given to the process that occurs when the cell is placed in solution Y?

            (b) Describe the process that would occur in a plant cell when placed in a similar solution as that

               of solution X                                                                                                           

8.         The figure below shows the results obtained when red blood cells are put in different solutions:-


(a) What is the name given to the process that occurs when the cell is put into solution B?

            (b) Compare the results obtained when the cell is put in solution B to the results that would be

                 obtained if a plant cell was put in the same solution                                                        

9.         Briefly state two adaptation for each of the following cells to their functions

             (i) Spermatozoon                                                                                                                  

            (ii) Palisade mesophlly   cell                                                                                                 

10.       The diagram below represents a cell at a certain stage in meiotic cell division

            a) Name the stage at which the cell drawn above represents                                                            

             b) Give a distinguishing reason for your answer in 21(a) above                                         

c) State any two differences between mitosis and meiosis                                                   

11.       What are two differences between tropisms and tactic movement   

12.       An experiment was carried out to investigate the effect of different concentrations of sodium

            chloride on human red blood cells. Equal amounts of blood were added to equal volumes of the

            salt solution but of different concentrations. The results are shown in the table below:      

Set -up Number of red blood cells
 Sodium chloride concentrationAt start of experimentAt the end of the experiment
A0.9%NormalNo change in number
B0.3%NormalFewer in number

            (a) Account for the results in the set-up

            (b) If the experiment was repeated using 1.4% sodium chloride solution, state the expected

                 results with reference to:

    (i) the number of red blood cells                                                                                              

                (ii) the appearance of red blood cells if viewed under the microscope

13.       Name support tissues in plants characterized by the following                                            

            (i) Cells being  turgid   

            (ii) Cells being thickened by cellulose   

            (iii) Cells being thickened by lignin  

14.       The diagram below illustrates the behaviour of red blood cells when placed into two different

solutions X and Y.

(a) Suggest the nature of solutions X and Y.                                                                         

(b) Name the process A and B.                                                                                              

 (c) What would happen to normal blood cell if it were placed in a solution isotonic.         

15.       Name two plant processes in which diffusion plays an important role                                 

16.       Two fresh potato cylinders of equal length were placed one in distilled water and the other in

            concentratedsucrose solution:

            (a) Account for the change in length of the cylinder in:

           (i) Distilled water                                                                                                              

           (ii) Sucrose solution                                                                                                          

             (b) (i) What would be the result in terms of length if a boiled potato was used?                

                  (ii) Explain your answer in(b)(i) Above                                                              

       (c) State two uses of the physiological process being demonstrated in the experiment      

17.       The two cells shown below are obtained from two different potato cylinders which were immersed in tow different solutions P and Q

a) i) Name the structure labelled A.                                                                                      

   ii) State the function of structure B.                                                                                   

b) If eight of cell I were observed across the diameter of the filed  of view of 0.5 mm.

    Work out the actual diameters of each cell in micrometers.                                              

c) Suggest the identity of the solution Q.                                                                              

d) Account for the change in cell I above.                                                                             

e) State any one importance of the physiological process being demonstrated above in animals.

18.       An experiment shown below was set-up to investigate a certain physiological process in plants:-

(a) What process was being investigated?                                                                             

            (b) Give the role of the oil layer in this experiment                                                              

            (c) (i) What observation did the students make after leaving the set-up in bright sunlight for

                       two hours?                                                                                                                               

                 (ii) Explain the observation in (c)(i) above                                                                                  

            (d) What effect will the following have on the observation made?:-

                   (i) Fanning the shoot       

                   (ii) Removing all the leaves from the shoot

                    (iii) Placing the set-up in the dark         

            (e) Suggest a suitable control for this experiment

19.       Study the following food web and answer questions that follow:  


(a) (i) Name the organisms that occupy the second trophic level                                          

                 (ii) What is the other name for the second trophic level                                                   

            (b) Write down two food chains from the food web that:                                                     

                (i) End with hawks as tertiary consumer

                (ii) End with hawks as quaternary consumer

            (c) Giving reasons state;

                        (i) the organism with largest biomass                                                                                                (ii) the organism with least biomass

ANSWERS FOR BIOLOGY TOPIC-Osmosis, Diffusion and Active Transport

1.         a) A-  The strip increased in length/ size; B –      Decreased in length/ size;

            b)The sugar solution was hypotonic to the cell sap strip A; it gained water by osmosis

               hence increasing in length;

2.         (a) The potato cup will be filled with solution;         

(b) The solution in the potato cells is hypertonic to the water; hence water moves into the cell by

      osmosis;  this makes the solution in the neighbouring cells to be hypertonic to the outer cells;  

      hence water moves from cell to cell until it eventually enters the potato cup;

3.         (a) (i) Will lose water by osmosis and become plasmolysed;                                               

4.         Diffusion;                                                                                                                               

            Osmosis ;

            Active transport ;       

5          a) 3.0 + 3.1 + 3.2 = 9.3 g;                                                                                                      

                        Average = 9.3 = 3.1g;


            b) The cell sap had a higher concentration of solutes than distilled water, water therefore

      moves  from the environment to the cell by osmosis ;    

6.         (a) red blood cells placed in a hypertonic solution and as a result lost water to the surrounding    

                  thorough osmosis hence shrunk/crenated ;                                                          

(b) Appearance of that cell if subjected to the same condition

7.         a) Haemolysis                                                                                                             

         b) Plant cell will lose water the cell sap to the outside solution by osmosis; the cell

             becomes plamolysed/ flaccid; but it will retain its shape due to rigid cell wall;

8.         a) Haemolysis  ;                                                                                                                      

            b) The plant cell will draw in water molecules by osmosis; it will swell and become turgid; but it

    will not burst because of the presence of cellulose cell wall;

9.         i) Spermatozoon                                                                                                                     

                        – Tail – For swimming in vagina tract

                        – Numerous mitochondria – for provision of energy for swimming

                        – Streamlined – to reduce friction during movement

                        – Haploid nucleus – for fertilization of haploid ovum

                        Palisade mesophyll cell

                        – Numerous chloroplasts for photosynthesis

                        – Narrow and cylindrical – packed in small space

                        – Large sap vacuole for storage of manufactured food;

10.       a) Prophase I Reject prophase alone                                                                                      

            b) Homologous Chromosomes side by side or Bivalency


One phaseTwo phases
Diploid daughter cellsHaploid daughter
No chiasmata formationChiasmata formation;   Any two correct
TrophismTactic response
Growth is involved or brought about cell divisionLocomotary
Set -up Number of red blood cells
 Sodium chloride concentrationAt start of experimentAt the end of the experiment
A0.9%NormalNo change in number
B0.3%NormalFewer in number

11.       A-no change  in; number because 0.9% sodium chlorine solution  is  isotonic to RBC/blood;

            B-fewer in number because  0.3%  sodium chloride  solution is  hypotonic  to RBC/blood

   therefore some water  was  drawn in to RDC by osmosis ;leading  to  haemolysis/boosting  of


             b)i)number  will not  change;

               ii)RBC  will appear small  in size/wrinkled/crenated/shriveled/shrink; 1mk

                 Rej. Flaccid/flabby/plasmolysed

12.     (i) Paranchyma;                                                                                                

         (ii) Collenchyma;

         (iii) Xylem: and sclerenchyma

13.       (a) X – hypotonic solution;                                                                                                     p

                 Y – hypertonic solution;                                                                                                    p

            (b) A – haemolysis;                                                                                                                 p.

                 B – crenation /laking;                                                                                                         p

            (c) The cell will maintain/retain its normal shape.    

14.       Absorption of mineral salts by root hairs from the soil; Translocation of food from

            leaves to other   parts of the plant; movement of salts from one cell to the next;                             

15.       (a) (i) Increased in length, absorbed water through   osmosis, ( since cylinder cells were

         hypertonic/ at  higher concentration) and become turgid.

         (ii) Reduced in length, cylinder host water to the hypertonic sucrose solution/become flaccid.

            (b) (i) No change in length

          (ii) Cells are dead and cannot carry out osmosis.

            (c) – opening and closing of stomata

  •             Support  in plants
  •             Movement of water from cell to cell
  • Feeding in insectivorous plants
  • Absorption of water by root hairs
  • Absorption  of water in the intestines
  • Reabsorption of water in kidney nephron.

16.       (a) (i) Nucleus                                                                                                                        

                (ii) Maintain the shape of he cell providing support to herbaceous plants; stores sugar

                      and  salts;                                                                        (mark first one)

(b) 0.5 x 100  ; 62.5µm;


(c) Hypotonic solution;

                Accept -highly concentrated salt/sugar solution

(d) The potato cell sap were lowly concentrated than the surrounding solution; hence lost water

      molecules by osmosis through the semi permeable membrane to become plasmolysed;

(e) Re-absorption of water from the kidney tubules/ hence important in osmoregulation;

17.       a) transpiration                                                                                                                       

            b) prevent  evaporation of water from the surface

            c) the level of  water  dropper

            d) i) faster  drop in water level                       ii) no change  in water level;

                 iii) slower/very  slow drop in water level;                                                                                              

      e) another set up using a leafless twig;