chapter 6 ii

Answer

Activity 1

a) 1. False                                                     b) P: Oxygen

2. True                                                           Q: Chlorophyll

3. True                                                           R: Hydrogen

4. False                                                          S: Glucose

5. True

6. False

7. False

8. True

Activity 2

Similarities                                                      Differences

1. chloroplast                                                  1. granum, stroma

2. chemical                                                     2. sunlight, sunlight

3. photosynthesis                                            3. photolysis, carbon dioxide

4. day                                                             4. oxygen, glucose

5. water, carbon dioxide

Activity 3

a) i)    Light intensity

    ii)   Carbon dioxide concentration

    iii)  Temperature

b)

• Carbon dioxide is a reactant required in photosynthesis
• Low concentration of carbon dioxide acts as a limiting factor to

      photosynthesis.

• As increasing in carbon dioxide concentration results in an increasing in the rate of photosynthesis until a saturation point is reached.
• At this point, low light intensity becomes a limiting factor and limits the

      photosynthetic process.

• Increasing the light intensity would increase the rate of photosynthesis until the saturation point is reached.
•  

                              Light energy

c)   6O₂ + 12CO₂                             C₆H₁₂O₆ + 6O₂  + 6H₂O                                            

                               chlorophyll

d)  i)  Glucose

ii)  Sucrose

e)  i)  Cellulose

         Main component of plant cell wall

    ii)  Protein

         Important component of cytoplasm

   iii)  Lipid

         Component of plasma membrane

Objective Items

1   B

2   A

3   B

4   D

5   A

6   C

7   B

8   B

9   B

10 C

Structured question

1   (a) ( i) The culture medium for jar B is the same as Knop’s culture solution except

               that calcium nitrate and potassium nitrate are replaced with calcium                  chloride and potassium chloride respectively.

          (ii)  The culture medium for jar C is the same as Knop’s culture solution                  except that calcium nitrate is replaced with magnesium nitrate.

     (b) (i)  To inhibit the growth of unicellular algae which were consume part of the                nutrients in the culture medium

          (ii) The roots of the seedlings need oxygen for respiration

          (iii) Part of the nutrients in the culture medium has been consumed by the                     seedlings

     (c) (i)  Leaves turn yellowish and drop

          (ii) The shapes of young leaves are irregular

     (d)      Nitrogen is needed for the synthesis of chlorophyll  

     (e)      No. Plants are unable to utilizes gaseous nitrogen

     (f)       Middle lamella  

Essay Question

1   (a)

     (b) Arrangement of the leaf

          The leaves are arranged in a mosaic pattern so that there is minimal                 overlapping and the leaves receive maximum sunlight.

          Shape of the leaf

          The leaf is flat, broad and thin. This increase the surface area for maximum           absorption of sunlight and carbon dioxide.

          Structure of the leaf

          Epidermis is translucent to allow sunlight to penetrate into the leaf.

          Cuticle layer is waxy and water-proof to prevent loss of water and to protect           the leaf

          Palisade cells are closely arranged and at right angles to the surface  of the           leaf. They also contain many chloroplasts to absorb maximum sunlight.

          Spongy mesophyll cells are loosely arranged to provide large air spaces for

           gaseous exchange

          Stoma allows exchange of gases between oxygen and carbon dioxide during

           photosynthesis and respiration

          Veins consist of vascular bundles. Each vascular bundle consists of xylem

           tissue to transport water and minerals from roots to the leaves and phloem

           tissue to transport the products of photosynthesis from the leaves to the other

           parts of the plant.

     (c) (i)  Role of chlorophyll

          Chlorophyll absorbs the energy from the sunlight. The energy is used to split           up the water molecules into hydroxyl ions and hydrogen ions. The hydroxyl           ions give up its electrons to chlorophyll to form hydroxyl groups which then           combined together to form water and oxygen. The hydrogen ions receive                     electrons from the chlorophyll to form hydrogen atoms.

          (ii) Role of water

          Water is split up during photolysis of water to form hydrogen which is used in           the reduction of carbon dioxide. Oxygen is released and water is also formed.

          (iii)  Role of carbon dioxide

          Carbon dioxide diffuses into the leaf through the stoma. In the chloroplast,                     carbon dioxide is reduced by hydrogen from the photolysis of water to form             basic units of glucose (CH₂O). Six basic glucose units combine to form a                  molecule of glucose (C₆H₁₂O₆).