IB HomeStandard LevelTopic 1: Statistical AnalysisTopic 2: CellsTopic 3: Chemicals of Life3.8 PhotosynthesisTopic 4: GeneticsTopic 5: Ecology and also EvolutionTopic 6: Health & PhysiologyHigher LevelTopic 7: Nucleic Acid & ProteinTopic 8: Respiration & Photo ..Topic 9: Plant ScienceTopic 10: GeneticsTopic 11: Health & PhysiologyOptionsOption A: Nutrition & HealthOption B: Physiology of ExerciseOption C: Energy and CellsOption D: EvolutionOption E: Neurobiology & Behav..Option F: Microbes & Biotech..Option G: Ecology & Conservat..Option H: More PhysiologyFurther Resources


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3.8 Photosynthesis


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3.8.1 State that photosynthesis entails the convariation of light power right into chemical energy

Photosynthesis is the process by which plants synthesise organic compounds (e.g. glucose) from not natural compounds (CO2 and H2O) in the existence of sunlight




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Photosynthesis is a 2 action process: 

1. The light dependent reactions convert the light energy into chemical power (ATP)

2. The light independent reactions use the chemical power to synthesise organic compounds (e.g. glucose)

The organic molecules developed in photosynthesis have the right to be offered in cellular respiration to carry out the energy necessary by the organism

3.8.2 State that light from the Sun is written of a selection of wavelengths (colours)

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Sunlight is white light, consisted of of all the colours of the visible spectrum

Colours are different wavelengths of light and also variety from ~ 400 nm - 700 nm

The colours of the visible spectrum are (from longer to shorter wavelength):

Red Orange  Yellow Eco-friendly Blue Indigo Violet (R.O.Y.G.B.I.V)

3.8.3 State that chlorophyll is the main photoman-made pigment

Chlorophyll is the major site of light absorption in the light dependent stage of photosynthesis

Tright here are a variety of various chlorophyll molecules, each through their own unique absorption spectra (the spectrum of light took in by a substance)

When chlorophyll absorbs light power, they release electrons which are used to make ATP (chemical energy)

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Chlorophyll and Photosystems

3.8.4 Overview the distinction in absorption of red, green and also blue light by chlorophyll

The main colours of light took in by chlorophyll are red and blue light

The primary colour of light not soaked up (it is reflected) by chlorophyll is green light

This explains why leaves are green - excepting once the existence of various other pigmented substances (e.g. anthocyanins) produces a various colourDeciduous trees speak developing high amounts of chlorophyll in the winter (as a result of inadequate sunlight), enabling other photoman-made pigments (e.g. xanthophylls, carotenoids) to involved the fore, which alters the colour of the leaf

3.8.5 State that light energy is offered to develop ATP, and to split water molecules (photolysis) to develop oxygen and also hydrogen

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The initially part of photosynthesis is the light dependent reactivity, which supplies light energy to make ATP

Light Dependent Reaction

Light stimulates chlorophyll to release electrons, which outcomes in the production of ATPLight power likewise splits water molecules (photolysis), creating oxygen and also hydrogenThe hydrogen is taken up by a hydrogen carrier (NADP+) to develop NADPHThe splitting of water additionally releases electrons, which rearea those shed by the chlorophyllThe ATP and hydrogen (NADPH) are taken to the site of the light independent reactions

3.8.6 State that ATP and hydrogen (acquired from the photolysis of water) are supplied to fix carbon molecules to make organic molecules

The second component of photosynthesis is the light independent reactivity, which provides organic compounds from the products of the light dependent reactions

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Light Independent Reaction

ATP and hydrogen (carried by NADPH) are commodities of the light dependent reactionsThey are provided to settle carbon molecules together (include CO2 to standard carbon compounds)This permits for the production of more complicated organic molecules (e.g. sugars)These organic molecules have the right to then be stored to usage in cellular respiration as required 

3.8.7 Exsimple that the rate of photosynthesis deserve to be measured straight by the production of oxygen or the uptake of carbon dioxide, or indirectly by a rise in biomass

The rate of photosynthesis can be measured by changes in the quantities of inputs (CO2) or outputs (O2 or glucose) of the photosynthesis equationWater cannot be measured as it is connected in a number of important procedures besides photosynthesis (e.g. condensation and hydrolysis reactions)

Measuring CO2 Uptake

CO2 uptake deserve to be measured by placing a plant in an enclosed space via waterCarbon dioxide interacts through the water molecules, producing bicarbonate and hydrogen ions, which increases the acidity of the resulting solutionThe adjust in pH have the right to therefore carry out a measure of CO2 uptake by a plant (boosted CO2 uptake = more alkaline pH)

Measuring O2 Production

O2 production deserve to be measured by submerging a plant in an enclosed area with water attached to a sealed gas syringeAny oxygen gas developed will certainly bubble out of solution and also can be measured by a change in water level (through the place of the meniscus)

Measuring Biomass (Indirect)

Glucose manufacturing have the right to be indirectly measured by a change in a plant"s biomass (weight)This needs the plant to be totally dehydrated before weighing to ensure the readjust in biomass reflects a change in organic issue and not water contentAn alternate approach for measuring glucose production is to recognize the adjust in starch levels in a plant (glucose is stored as starch)Starch deserve to be identified via iodine staining (resulting solution turns purple) and also quantitated utilizing a colorimeter

3.8.8 Synopsis the result of temperature, light intensity and carbon dioxide concentration on the price of photosynthesis

Temperature

Photosynthesis is controlled by enzymes, which are sensitive to temperatureAs temperature boosts, the price of photosynthesis will rise as reagents have better kinetic energy and are even more most likely to reactAbove a specific temperature, the rate of photosynthesis will decrease as vital enzymes start to denature

Light Intensity

As light intensity rises, the price of photosynthesis will certainly rise up until a specific point, when photosynthesis is proceeding at its maximum rateAdditional boosts to light intensity will have no impact on photosynthesis (the price will certainly plateau), as chlorophyll are saturated by lightDifferent wavelengths of light will certainly have various impacts on the price of photosynthesis (e.g. green light will not be used)

CO2 Concentration

As the concentration of carbon dioxide rises, the rate of photosynthesis will certainly rise up until a particular point, when photosynthesis is proceeding at its maximum rateMore rises to carbon dioxide concentration will certainly have no impact on photosynthesis (the price will certainly plateau), as the enzymes responsible for carbon fixation become saturated