introduction to botany. lecture 17
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Questions and answersPhotosynthesis
Introduction to Botany. Lecture 17
Alexey Shipunov
Minot State University
October 12th, 2011
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
Outline
1 Questions and answers
2 PhotosynthesisHistoryChloroplastLight stage: electron transport, synthesis of ATP andNADPH
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
Outline
1 Questions and answers
2 PhotosynthesisHistoryChloroplastLight stage: electron transport, synthesis of ATP andNADPH
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
Previous final question: the answer
Please invent a multiple choice test question for the secondexam
(subject: root, stem or leaf).There should be at least three exclusive choices.
10 questions went to the exam!
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
Previous final question: the answer
Please invent a multiple choice test question for the secondexam
(subject: root, stem or leaf).There should be at least three exclusive choices.
10 questions went to the exam!
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
HistoryChloroplastLight stage: electron transport, synthesis of ATP and NADPH
Green slugs
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
HistoryChloroplastLight stage: electron transport, synthesis of ATP and NADPH
Green Hydra
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
HistoryChloroplastLight stage: electron transport, synthesis of ATP and NADPH
van Helmont
Johannes van Helmont (17th century) rejected the ideathat plans take most of their biomass from soilWillow (Salix sp.) tree of 2.27 kg grew to 67.7 kg in fiveyears, but weight of soil decreased only by 57 gvan Helmont concluded that plants take most of theirweight from water
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
HistoryChloroplastLight stage: electron transport, synthesis of ATP and NADPH
Pristley
Famous Joseph Pristley in 1772, made series ofexperiments with mouse, candle and sprig of mint (Menthasp.)Mouse behave similar to candle, they both “spent” airPlant revives the air for both candle and mouse
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
HistoryChloroplastLight stage: electron transport, synthesis of ATP and NADPH
Further history
J. Ingen-Houst (1779–1796) and J. Senebier (1780) found that:
“Experiments upon vegetables, discovering their greatpower of purifying the common air in the sunshine and ofinjuring it in the shade and at night, to which is joined anew method of examining the accurate degree of theatmosphere”CO2 is assembled
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
HistoryChloroplastLight stage: electron transport, synthesis of ATP and NADPH
Engelmann
T.W. Engelmann in 1884 found that Spirogyra alga produceoxygen mostly in blue and red parts of spectrumTherefore, the key photosynthetic pigment should acceptblue and red rays and reflect green raysChlorophyll fits best to this description
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
HistoryChloroplastLight stage: electron transport, synthesis of ATP and NADPH
Experiment of Engelmann
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
HistoryChloroplastLight stage: electron transport, synthesis of ATP and NADPH
Blackman
In 1905, F.F. Blackman discovered that if light intensity islow, increase of temperature has a little effect on the rate ifphotosynthesisConsequently, photosynthesis has two stages:
1 Light stage which relates more with light intetsity2 “Dark” (now called enzymatic or light-independent) stage
which relates more with temperature
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
HistoryChloroplastLight stage: electron transport, synthesis of ATP and NADPH
Light and enzymatic (“dark”) reactions
Light reactions depend on the light and water, theyproduce oxygen and energy (in form of ATP)Enzymatic reactions depend on carbon dioxide and water,they take energy from light reactions and result inproduction of carbohydratesMain component of enzymatic reactions called Calvin cyclewhich fixates carbon dioxide
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
HistoryChloroplastLight stage: electron transport, synthesis of ATP and NADPH
Equation
6CO2 + 6H2Olight−−−→ C6H1206 + 6O2 is not a formula, but
merely a general description of a processWater molecules arise from both sides, and the betterformula is
6CO2 + 12H2Olight−−−→ C6H1206 + 6H20 + 6O2
or even
carbon dioxide + hydrogen donorlight−−−→ carbohydrate + water +
oxidized hydrogen donor
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
HistoryChloroplastLight stage: electron transport, synthesis of ATP and NADPH
Compartments of chloroplast
Even isolated chloroplasts may take light and fixate carbondioxidePhotosynthesis is related with membrane system(tylacoids) of chloroplasts, which has two parts:
1 grana2 stroma lamellum
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
HistoryChloroplastLight stage: electron transport, synthesis of ATP and NADPH
Stroma
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
HistoryChloroplastLight stage: electron transport, synthesis of ATP and NADPH
Tylacoids
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
HistoryChloroplastLight stage: electron transport, synthesis of ATP and NADPH
Division of labor in chloroplast
Light reactions are concentrated around tylacoidmembranes, tylacoids are also H+ (protons, hydrogenions) reservoirEnzymatic reactions run in stroma (chloroplast“cytoplasm”)
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
HistoryChloroplastLight stage: electron transport, synthesis of ATP and NADPH
Location of two stages
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
HistoryChloroplastLight stage: electron transport, synthesis of ATP and NADPH
Participants of light stage
1 Chlorophyll2 Light3 Water4 ATP synthase5 Protons (H+)6 Hydrogen carrier (NADP+)7 Place: around tylacoid membrane
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
HistoryChloroplastLight stage: electron transport, synthesis of ATP and NADPH
Main events of light stage
1 Chlorophyll + Light −→ Electron (e−) + Chlorophyll+
2 H2O −→ H+ + OH− (accumulates outside)3 e− + H+ + Hydrogen carrier (NADP+) −→ NADPH (moves
away)4 H2O −→ H+ (accumulates inside) + e− + O2
5 H+ (inside) + OH− (outside) −→ gradient −→ PROTONPUMP −→ ADP + Pi (inorganic phosphate) −→ ATP
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
HistoryChloroplastLight stage: electron transport, synthesis of ATP and NADPH
Summary
From 17th century, in constantly become clear that plantsmake their biomass from light, water and carbon dioxidePhotosynthesis is a sum of light-dependent andlight-independent reactionsLight reactions are concentrated around tylacoidmembrane whereas enzymatic reactions concentrate instroma
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
HistoryChloroplastLight stage: electron transport, synthesis of ATP and NADPH
Final question (2 points)
Which conclusions can be drawn from Pristley’s experiments?Please list more than one.
Shipunov BIOL 154.17
Questions and answersPhotosynthesis
HistoryChloroplastLight stage: electron transport, synthesis of ATP and NADPH
Final question (2 points)
Which conclusions can be drawn from Pristley’s experiments?Please list more than one.
Shipunov BIOL 154.17
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