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PHOTOSYNTHESIS
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Review Question Which mode of nutrition do the green plants carry out?
A. Autotrophic nutrition B. Heterotrophic nutrition
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Sorry! You’re wrong! Heterotrophic nutrition is the mode of nutrition in which organisms have to depend on other organisms or dead organic matters as their food sources. Green plants, however, can make organic food by themselves using simple inorganic substances. Back
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Very Good! Photosynthesis
Autotrophic nutrition is the mode of nutrition in which organisms can make organic food by themselves using simple inorganic substances. The process by which the green plants obtain nutrients is called :- Photosynthesis
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Overview of nutrition in green plants
carbon dioxide and water photosynthesis mineral salts (e.g. NO3-, SO42-) carbohydrates (e.g. glucose) fatty acids glycerol amino acids water nutrients for plants can be used to produce all plant materials (e.g. enzymes, cell wall, cytoplasm, cell membrane, chlorophyll)
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Nature of photosynthesis
Anabolic process Takes place in chloroplast Necessary factors : Carbon dioxide Water Sunlight Chlorophyll
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Light
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Light Absorption Spectrum
Why leave looked green?
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Different pigments in absorption spectrum
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How light energy used?
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Light reaction Light energy is trapped by chlorophyll in chloroplast
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Light reaction Light energy absorbed by chlorophyll splits water molecules into hydrogen and oxygen
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Light reaction Oxygen is released as a gas through stoma to outside
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Light reaction Hydrogen is fed into dark reaction
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Dark reaction Water is formed as a by-product No light is required; can take place either in light or darkness Hydrogen produced in light reaction combines with CO2 to form carbohydrates
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Chlorophyll Structure
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Photophosphorylation
Light Reaction Photophosphorylation
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Cyclic photophosphorylation
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Dark Reaction M. Calvin
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Calvin Cycle
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CHLOROPLAST
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Fate of product of photosynthesis
PGAL Pyruvate + coenzyme A X 2 Glucose & Cellulose Kreb cycle Fatty acid Glycerol Nitrate Lipid Protein
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Factors affect rate of photosynthesis
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Expt. Show effect of factors
Conc. Of NaHCO3 Distance Heat
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Fate of carbohydrate products in the plant
carbon dioxide and water photosynthesis mineral salts (e.g. NO3-, SO42-) carbohydrates (e.g. glucose) fatty acids glycerol amino acids water
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Fate of carbohydrate products in the plant
carbon dioxide and water photosynthesis mineral salts (e.g. NO3-, SO42-) carbohydrates (e.g. glucose) fatty acids glycerol amino acids water release energy by respiration
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Fate of carbohydrate products in the plant
carbon dioxide and water photosynthesis mineral salts (e.g. NO3-, SO42-) carbohydrates (e.g. glucose) fatty acids glycerol amino acids water convert into starch for storage
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Fate of carbohydrate products in the plant
carbon dioxide and water photosynthesis mineral salts (e.g. NO3-, SO42-) carbohydrates (e.g. glucose) fatty acids glycerol amino acids water change into sucrose and is transported to other parts through phloem
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Fate of carbohydrate products in the plant
carbon dioxide and water photosynthesis mineral salts (e.g. NO3-, SO42-) carbohydrates (e.g. glucose) fatty acids glycerol amino acids water combine to form fats and oils to form cell membranes and as a food store
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Fate of carbohydrate products in the plant
carbon dioxide and water photosynthesis mineral salts (e.g. NO3-, SO42-) carbohydrates (e.g. glucose) fatty acids glycerol amino acids water join together to become protein molecules
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Mineral requirements in plants
In order to synthesize amino acids, nitrate ions must be taken into the plant from the soil through the root Other minerals are also necessary to maintain the life of the plant
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Expt. Show effect of minerals
Different Nutrient added
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The importance of nitrogen
For synthesis of proteins, chlorophyll, etc. Taken in the form of nitrate ions Deficiency symptoms: Little growth (no protein made) Yellowing of leaves (chlorophyll made)
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The importance of magnesium
Essential component of chlorophyll Deficiency symptoms: Yellowing of leaves (no chlorophyll made) Poor growth (no food manufactured because of lack of chlorophyll)
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Use of fertilizers in agriculture
Continuous harvesting crops removes the valuable mineral salts from soil Fertilizers are added to replace such loss Two kinds of fertilizers: Natural fertilizers Chemical fertilizers
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Natural fertilizers From manure
Organic compounds in it are decomposed by bacteria in soil to form mineral salts
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Chemical fertilizers Mainly nitrogenous and phosphorous compounds manufactured artificially
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Comparison between natural and chemical fertilizers
Natural fertilizers Chemical fertilizers Very cheap More expensive Contain humus which can improve soil texture No humus so cannot improve soil texture Less soluble in water so less likely to be washed away Very soluble in water so more likely to be washed away
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Comparison between natural and chemical fertilizers
Natural fertilizers Chemical fertilizers Less soluble in water so more difficult to be absorbed Very soluble in water so easier to be absorbed Time is needed for the decomposition to complete before nutrient is available to plants More readily to be used by the plants
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Importance of photosynthesis
It is the only method to convert energy in sunlight into chemical energy Animals have to depend on plants for food supply Plants: producers; animals : consumers To maintain a constant oxygen level in the atmosphere
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Experiments to test for necessary factors of photosynthesis
Experimental set-up: To remove the factor under study and to see if photosynthesis still takes place Control set-up: Identical to experimental set-up except that the missing factor is present
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A set-up to study whether light is necessary for photosynthesis
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Which is the control, the exposed region A or the shaded region B?
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What is the purpose of setting up region A?
As a control Too simple and not explicit! To show that photosynthesis cannot take place in the absence of light
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Destarching Reason: Method:
To avoid any existing starch in the leaves interfering with the result, and to show that any starch found after the experiment was produced during the period of investigation Method: By placing the plant in dark for at least 24 hours
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Parts of plant where photosynthesis takes place
Places where chloroplasts are found Mainly in the leaf because it contains a lot of chloroplasts it is well adapted for performing photosynthesis
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Cross-section of a dicot leaf
upper epidermis protect internal tissues from mechanical damage and bacterial and fungal invasion
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Cross-section of a dicot leaf
Cuticle a waxy layer prevent water loss from the leaf surface
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Cross-section of a dicot leaf
mesophyll
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Cross-section of a dicot leaf
palisade mesophyll contains many chloroplasts columnar cells closely packed together absorb light more efficiently
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Cross-section of a dicot leaf
irregular cells loosely packed together to leave numerous large air spaces allow rapid diffusion of gases throughout the leaf less chloroplasts for photosynthesis spongy mesophyll
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Cross-section of a dicot leaf
same as upper epidermis except the cuticle is thinner lower epidermis
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Cross-section of a dicot leaf
stoma opening which allows gases to pass through it to go into or out of the leaf
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Cross-section of a dicot leaf
guard cells control the size of stoma
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Cross-section of a dicot leaf
vascular bundle (vein)
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Cross-section of a dicot leaf
xylem to transport water and mineral salts towards the leaf
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Cross-section of a dicot leaf
phloem to transport organic substances away from the leaf
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Adaptation of leaf to photosynthesis
Upper epidermis and cuticle is transparent Allows most light to pass to photosynthetic mesophyll tissues
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Adaptation of leaf to photosynthesis
Palisade mesophyll cells are closely packed and contain many chloroplasts To carry out photosynthesis more efficiently
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Adaptation of leaf to photosynthesis
Spongy mesophyll cells are loosely packed with numerous large air spaces To allow rapid diffusion of gases throughout the leaf
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Adaptation of leaf to photosynthesis
Numerous stomata on lower epidermis To allow rapid gaseous exchange with the atmosphere
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Adaptation of leaf to photosynthesis
Extensive vein system Allow sufficient water to reach the cells in the leaf To carry food away from them to other parts of the plant
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CHEMOSYNTHSIS Iron bacteria Colorless sulphur bacteria
Nitrifying bacteria
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Iron bacteria
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Nitrifying bacteria
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