Page 140 - General and Inorganic Chemistry for Advanced Secondary Schools Students Book Form Five and Six

Biology for Secondary Schools

Chapter summary

1. Photosynthesis is the process by which green plants, some bacteria and
some protoctists make their own food using carbon dioxide and water
in the presence of sunlight.
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2. A plant leaf comprises features that make it well adapted to
photosynthesis.
(a) Waxy transparent cuticle
(b) Thin epidermis with stomata
(c) Palisade cells with chloroplasts
(d) Palisade cells positioned just below the upper epidermis
(e) Spongy mesophyll with air space
(f) Veins that have vascular tissue
(g) Broad flat lamina
(h) Petiole to attach the leaf to the stem or branch at an appropriate
angle to access sunlight

3. Photosynthesis involves two stages, namely the light reaction stage and
the dark reaction stage.

4. During the light reaction stage, sunlight causes the production of ATP
and splitting of water molecules into hydrogen and hydroxyl ions. This
reaction is called photolysis.
5. In the dark reaction stage, carbon dioxide and hydrogen ions combine to
form glucose. This reaction is called carbon dioxide fixation. Glucose is
later used to make starch, proteins and lipids.

6. Plants require both macroelements and microelements to survive.

7. The macroelements include nitrogen, phosphorus, potassium, sulphur,
calcium, and magnesium.
8. The microelements include boron, copper, iron, chlorine, manganese,
molybdenum, and zinc.

9. Lack of the necessary elements affects plant growth and crop yields.
However, excessive amounts have negative effects. Plants should get
optimum amount of minerals.

134 Student’s Book Form One Student’s Book Form One

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