Microsoft Word - Bk1Ch06sPhotosynthesis.doc

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1 Chapter 6 Photosynthesis Summary Bk1 Ch06 Photosynthesis/1 Table 1: The significance of photosynthesis (Section 6.1) Synthesis of complex organic molecules from simple inorganic molecules Photosynthesis Converting light energy into chemical energy for the synthesis of organic substances in plants Sunlight is trapped by chlorophyll Mode of nutrition: autotrophic nutrition Occurs in plants, algae and certain bacteria (autotrophs) Table 2: Requirements for photosynthesis (Section 6.2; Fig. 6.12) Light Ultimate source of energy Absorbed by chlorophyll in plant cells Held in small, disc-shaped chloroplasts Chlorophyll Carbon dioxide Water Chloroplasts are found in the cytoplasm of the photosynthetic cells Gives rise to the green colour of the plant Plants fail to produce chlorophyll will develop yellowish leaves and are weak and small in size Chloroplasts contain enzymes that catalyze reactions in photosynthesis A raw material of photosynthesis Plants obtain it from the atmosphere For the synthesis of carbohydrates Diffuses through the pores on the leaf surfaces into the spaces between the cells Diffuses into the cells and reaches the chloroplasts A raw material of photosynthesis Plants obtain it from the soil by root hair cells Transported to photosynthetic cells Table 3: Test for the occurrence of photosynthesis of a plant (Section 6.2) Test for the presence of starch by iodine test Destarch the plant before the experiment Detach a leaf and put it in boiling water to kill the cells Put the leaf in boiling alcohol to dissolve the chlorophyll Soften the leaf by putting it in warm water Detect the presence of starch by iodine test 1

2 Table 4: Photosynthetic process (Section 6.3) Description A complicated process Consists of a series of reactions that are catalyzed by enzymes All reactions take place inside the chloroplasts Light energy is converted into chemical energy which is stored in the carbohydrates produced Carbon dioxide and water are converted into carbohydrates Oxygen is released as a by-product Divided into two stages: light-dependent stage and light-independent stage Carbon dioxide + Water Overall process of photosynthesis Bk1 Ch06 Photosynthesis/2 Light Carbohydrates + Oxygen Chlorophyll Table 5: Light-dependent stage and light-independent stage (Section 6.3; Fig. 6.18) Takes place only in the presence of light Light-dependent stage (light reaction) Light-independent stage (dark reaction) Starts with trapping of light energy by chlorophyll molecules Light energy is used to split water into hydrogen and oxygen (photolysis) Hydrogen is taken up by carriers and will be used in the light-independent stage Oxygen is released as a by-product Takes place irrespective of light is present or not Hydrogen (from light-dependent stage) combines with carbon dioxide to from carbohydrates, in the form of glucose (carbon fixation) Water is produced as a by-product Water Hydrogen + Oxygen Carbon dioxide + Hydrogen Carbohydrates + Water 2

3 Bk1 Ch06 Photosynthesis/3 Table 6: Environmental factors affecting the rate of photosynthesis (Extension Study) (Section 6.4) Light intensity Carbon dioxide concentration Temperature Water Higher light intensity results in a faster rate of photosynthesis Higher content of carbon dioxide in the surroundings leads to a faster rate of photosynthesis (air normally contains % of carbon dioxide) Higher temperature leads to a higher rate of metabolism, and the rate of photosynthesis will be higher If it exceeds a certain level, enzymes activities in plant cells will be inhibited and the rate of photosynthesis will decrease Its effect on the rate of photosynthesis is relatively indirect Plants absorb insufficient amount of water, resulting in a slower rate of photosynthesis Table 7: Formation of glucose during photosynthesis (Extension Study) (Section 6.5) During the daytime During the nighttime Glucose is formed rapidly in leaves Starch is converted back to a sugar (usually sucrose) Used up locally as an energy source Converted to starch for temporary storage in the leaf cells Transported away from the leaves to various parts of the plant Broken down into glucose for the release of energy Converted back to starch for storage Stored as sucrose or other carbohydrates Table 8: Different ways of utilization of photosynthetic products (Extension Study) (Section 6.5; Fig. 6.22) Glucose Intermediate products of photosynthesis Broken down to release energy Converts to sucrose Forms starch Forms cellulose Form fats Form amino acids (together with minerals obtained from the soil) Proteins For transport and storage For storage Structural material of the cell wall For storage Components of the cell membrane Components of the cytoplasm and cell membrane Formation of enzymes 3

4 Bk1 Ch06 Photosynthesis/4 Table 9: Leaf as a photosynthetic organ (Section 6.6) Characteristics of a leaf A main plant organ specialized for photosynthesis Contains most of the chloroplasts of a plant Consists of a lamina, which is attached to the stem by a petiole or leaf stalk Midrib is the extended part of the petiole and may branch into a network of veins or parallel veins Table 10: Structural adaptations of the leaf (Section 6.6) Typically broad and flat Provides a large surface area for absorption of sunlight Thin nature Allows movement of gases in and out of the cells quickly by diffusion Extensive network of veins Provides an efficient transport of materials 4

5 Bk1 Ch06 Photosynthesis/5 Table 11: Internal structure of a leaf (Section 6.6; Figs and 6.27) Structure Description Function A layer of closely fitted cells covered on the upper and lower surfaces Important in protecting the cells inside the leaf Epidermal cells A thin layer of waxy cuticle on the outer surface of the upper and lower epidermis Reduces the loss of water by evaporation from inner tissues Epidermis Epidermal cells do not contain chloroplasts Stomata Small pores appeared on the epidermal surface (Fig. 6.28) Enable the exchange of gases between the air and air spaces inside the leaf Guard cells Each stoma is bounded by a pair of guard cells Contain chloroplasts Control the size of the stoma Carry out photosynthesis Palisade mesophyll cells Closely packed and relatively regular in shape Contain dense chloroplasts Carry out photosynthesis Mesophyll Spongy mesophyll cells Loosely packed and relatively irregular in shape Presence of numerous interconnecting air spaces between the cells Enable exchange of gases Contain less chloroplasts Carry out photosynthesis Embedded in the mesophyll layer Midrib and veins Contain vascular tissues for efficient transport of substances towards and away from the leaf Xylem conducts water and minerals from the root to the leaf Phloem carries nutrients (usually sucrose) away from the leaf Contain thick-walled cells Support and maintain the shape of a leaf 5

6 Bk1 Ch06 Photosynthesis/6 Glossary Vocabulary 詞彙 Page Description 解釋 autotroph 自養生物 143 organism which is capable of synthesizing its own required nutrients from simple inorganic substances autotrophic nutrition 自養營養 143 a mode of nutrition which organisms make their own food by using simple inorganic substances to build up complex organic substances chlorophyll 葉綠素 89, 143 the green pigment in plants that absorbs light energy to carry out photosynthesis photosynthesis 光合作用 143 process by which plants use light energy to synthesize sugar from carbon dioxide and water chemosynthesis 化合作用 144 process of synthesis of compounds using energy obtained from the oxidation of inorganic compounds destarching 脫澱粉 148 the process to remove starch from a plant by keeping the plant in dark for two days or more coleus 洋紫蘇 150 herbs of the genus Coleus in the mint family, with multi-coloured leaves variegated leaf 斑葉 150 leaf that shows different pigmentation apart from green chloroplast 葉綠體 89, 152 the organelle in plant cells containing chlorophyll carotenoid 類胡蘿蔔素 154 a group of pigments occurring in some plants or animal tissues, giving a orange-red colour, including carotene, xanthophylls, and other fat-soluble pigments pigment 色素 89, 154 the natural colouring matter in the cells of organisms 能夠以簡單無機物合成本身所需要的有機食物的生物指生物運用簡單無機物來建立複雜有機物, 自製食物的營養模式植物中吸收光能來進行光合作用的綠色色素植物利用光能, 以二氧化碳與水合成糖的過程透過利用氧化無機化合物時所產生的能量, 合成化合物的過程將植物放入黑暗處 2 天或以上, 藉以去掉葉內的澱粉的過程歸類為薄荷科洋紫蘇屬的草本植物, 其葉片呈多種顏色顯現除綠色以外, 其他色素的葉片植物細胞中的細胞器, 內含葉綠素一組在部分植物或動物組織中出現的色素, 呈橙紅色, 當中包括胡蘿蔔素葉黃素以及其他脂溶性色素生物身體細胞中天然的有色的物質 light reaction 光反應 155 see light-dependent stage --- light-dependent stage 光反應 155 the reaction in photosynthesis in which light is required for the photolysis of water 在光合作用中, 需要利用光來光解水的反應 6

7 Vocabulary 詞彙 Page Description 解釋 photolysis 光解作用 155 the splitting of water molecule by means of light energy in photosynthesis, also see light-dependent stage carbon fixation 固碳作用 156 process by which green plants use up carbon dioxide to produce carbohydrates, the second stage of photosynthesis, also see dark reaction dark reaction, light-independe nt stage 暗反應 156 the reaction in photosynthesis that do not require light, carbon dioxide is converted into carbohydrates Bk1 Ch06 Photosynthesis/7 在光合作用中, 利用光能分裂水分子的過程, 亦見光反應植物耗用二氧化碳來產生碳水化合物的過程, 是光合作用的第二階段, 亦見暗反應光合作用中毋需光的反應, 二氧化碳在過程中轉化成碳水化合物 lamina 葉身 166 the blade of leaf 葉片闊大扁平的部分 leaf stalk 葉柄 166 the stalk that supports the leaf blade on the stem midrib 中脈 166 the central vein running longitudinally along a leaf, containing the xylem and phloem vessels 在葉片底部一條堅韌的構造, 以支撐葉身伸出於莖之外沿葉身縱向伸延的葉脈, 內含木質導管和韌皮導管 petiole 葉柄 166 see leaf stalk --- vein 葉脈 166 branching strands of vascular tissue in the leaf cuticle 角質層 167 a waxy, waterproofing layer secreted by plant epidermal cells, found mainly in leaves epidermal cell 表皮細胞 167 cells on the epidermis of a plant, plant epidermal cells contain no chloroplast epidermis 表皮 96, 167 the outermost layer of cells in plants or animals guard cell 保細胞 168 the cell enclosing the pore of a stoma, with uneven thickness of cell wall and regulates the size of the pore by variation in its turgidity mesophyll cell 葉肉細胞 168 layers of cells within a leaf between the upper and lower epidermal layers palisade mesophyll 柵狀葉肉 168 a layer or layers of elongated, compactly arranged photosynthetic cells just beneath the upper epidermis of a leaf 葉片中維管組織的幼小分支由植物的表皮細胞分泌出的一層不透水的蠟質層, 主要在葉面出現在植物或動物表皮的一層細胞, 植物細胞表皮不含葉綠體動植物身體表面, 由細胞組成的最外層包圍氣孔的細胞, 每個氣孔由兩個保衛細胞包圍, 細胞壁厚度並不平均, 透過細胞硬脹度的改變來控制氣孔的大小夾在葉片上表皮層和下表皮層中間的細胞層在葉的上表皮之下, 延伸成長形且緊密地排列的一層或多層細胞, 細胞會進行光合作用 7

8 Bk1 Ch06 Photosynthesis/8 Vocabulary 詞彙 Page Description 解釋 phloem 韌皮部 168 part of the vascular tissue in plant, extends throughout the plant body; responsible for transportation of organic materials spongy mesophyll stoma (pl. stomata) 海綿葉肉 168 a layer or layers of loosely-packed cells of irregular shapes separated by large air spaces; lies below the palisade mesophyll of a leaf 氣孔 168 small opening in the epidermis of plant body (mainly on lower epidermis of leaves) that allows gases and water vapour to enter or leave xylem 木質部 168 part of the vascular tissue in plant, a woody supporting tissue, a hollow tube for transporting water and minerals from the root through the stems to the leaves and other plant organs 植物維管組織的一部分, 延伸於整個植物物體中 ; 是有機物質運輸的部分緊接在柵狀葉肉以下的一層或多層細胞, 細胞形狀不規則, 並疏鬆地分佈, 細胞之間有許多大的氣室植物表皮上 ( 主要是葉的下表皮 ) 供氣體及水蒸氣進出的細小開口植物維管組織的一部分, 是木質的支持組織, 作為一條空心導管, 把水和礦物從根部經莖運輸到葉片等植物構造 8

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