Chapter Chapter 77Photosynthesis: Using Light to Make Food
Copyright © 2009 Pearson Education, Inc.
PowerPoint Lectures for
Biology: Concepts & Connections, Sixth Edition
Campbell, Reece, Taylor, Simon, and Dickey
Lecture by Richard L. MyersTranslated by Nabih A. Baeshen
Introduction: Plant Power
� Plants use water and atmospheric carbon dioxide to produce a simple sugar and liberate oxygen– Earth’s plants produce 160 billion metric tons of sugar
each year through photosynthesisphotosynthesisphotosynthesisphotosynthesis, a process that converts solar energy to chemical energy
– Sugar is food for humans and for animals that we consume consume
Carbon dioxide ثاني اكسيد الكربون
C6H12O6
Photosynthesis البناء الضوئي
H2OCO2 O2
Water
+ 66
Lightenergy
Oxygen gasغاز ا�كسجين
Glucoseجلوكوز
+ 6
الطاقة الضوئية
AN OVERVIEW OF PHOTOSYNTHESISOF PHOTOSYNTHESIS
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7.1 Autotrophs are the producers of the biosphere
� AutotrophsAutotrophsAutotrophsAutotrophs are living things that are able to make their own food without using organic molecules derived from any other living thing– Autotrophs that use the energy
of light to produce organic molecules are called
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molecules are called photoautotrophsphotoautotrophsphotoautotrophsphotoautotrophs
– Most plants, algae and other protists, and some prokaryotes are photoautotrophsphotoautotrophsphotoautotrophsphotoautotrophs
Kelp, a large algae الكيلب طحلب كبير
7.1 Autotrophs are the producers of the biosphere
� The ability to photosynthesize is directly related to the structure of chloroplasts– ChloroplastsChloroplastsChloroplastsChloroplasts are organelles consisting of photosynthetic pigments, organelles consisting of photosynthetic pigments, enzymesenzymesenzymesenzymes, and other molecules grouped together in membranes
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Micrograph of cyanobacteria
(photosynthetic bacteria)(
7.2 Photosynthesis occurs in chloroplasts in plant cells
� ChloroplastsChloroplastsChloroplastsChloroplasts are the major sites of photosynthesis in green plants– ChlorophyllChlorophyllChlorophyllChlorophyll, an important light absorbing pigment in chloroplasts, is responsible for the green color of responsible for the green color of plants– Chlorophyll Chlorophyll Chlorophyll Chlorophyll plays a central role in converting solar energy to chemical energy
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Vein
Mesophyll
Leaf Cross Section
7.2 Photosynthesis occurs in chloroplasts in plant cells
CO2 O2Stoma
Mesophyll Cell
ChloroplastThe location and structureof chloroplasts
7.2 Photosynthesis occurs in chloroplasts in plant cells
� ChloroplastsChloroplastsChloroplastsChloroplasts are concentrated in the cells of the mesophyllmesophyllmesophyllmesophyll, the green tissue in the interior of the leafStomataStomataStomataStomata are tiny pores in the leaf that � StomataStomataStomataStomata are tiny pores in the leaf that allow carbon dioxide to enter and oxygen to exit
� Veins Veins Veins Veins in the leaf deliver water absorbed by rootsCopyright © 2009 Pearson Education, Inc.
Chloroplast
Outer and innermembranes
Intermembranespace
Thylakoidspace
GranumStroma ThylakoidSpace
7.2 Photosynthesis occurs in chloroplasts in plant cells
�An envelope of two membranes encloses the stromastromastromastroma, the dense fluid within the chloroplast�A system of interconnected membranous sacs called thylakoidsthylakoidsthylakoidsthylakoids segregates the stroma from another compartment, the thylakoid spacethylakoid spacethylakoid spacethylakoid spaceanother compartment, the thylakoid spacethylakoid spacethylakoid spacethylakoid space
–ThylakoidsThylakoidsThylakoidsThylakoids are concentrated in stacks called granamgranamgranamgranam
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7.3 Plants produce O2 gas by splitting water
� Scientists have known for a long time that plants produce O2, but early on they assumed it was extracted from CO2 taken into the plant–Using a heavy isotope of oxygen, 18O,
they showed with tracer experimentsthat O actually comes from H O
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that O2 actually comes from H2O
Oxygen bubbles on the leaves of an aquatic plant
6 COO22 + 12 H2O
Experiment 1
C6H12OO66 + 6 H2OO + 6 O2
Not labeled
Experiment 2
6 CO2 + 12 H2OO
Experiment 2
C6H12O6 + 6 H2O + 6 OO22
Labeled
Experiments tracking the oxygen atoms in photosynth esisExperiments tracking the oxygen atoms in photosynth esis
Reactants: 6 CO2 12 H2O
Fates of all the atoms in photosynthesis
Products: C6H12O6 6 H2O 6 O2
7.4 Photosynthesis is a redox process, as is cellular respiration
� Photosynthesis, like respiration, is a redox (oxidation-reduction) process– Water molecules are split apart by
oxidation, which means that they lose oxidation, which means that they lose electrons along with hydrogen ions (H+)
– Then CO2 is reduced to sugar as electrons and hydrogen ions are added to it
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6 CO2 + 6 H2O C6H12O6 + 6 O2
Reduction
Oxidation
Photosynthesis (uses light energy)
6 CO2 + 6 H2O + EC6H12O6 + 6 O2
Reduction
Oxidation
Cellular respiration (releases chemical energy)
7.4 Photosynthesis is a redox process, as is cellular respiration
� Recall that Recall that Recall that Recall that cellular respiration cellular respiration cellular respiration cellular respiration uses redox uses redox uses redox uses redox reactions to harvest the chemical energy stored in reactions to harvest the chemical energy stored in reactions to harvest the chemical energy stored in reactions to harvest the chemical energy stored in a glucose moleculea glucose moleculea glucose moleculea glucose molecule– This is accomplished by oxidizing the sugar and reducing O2 to H2Oreducing O2 to H2O– The electrons lose potential as they travel down an energy hill, the electron transport system– In contrast, the food-producing redox reactions of photosynthesis reverse the flow and involve an uphill climb
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H2O
NADP+
ADPP
LIGHT REACTIONS
Light
Chloroplast
(in thylakoids)
An overview of the two stages ofphotosynthesis that take place in a chloroplast
H2O
ADPP
LIGHTREACTIONS
NADP+
Lightضوء
Chloroplast ب!ستيدة خضراء
REACTIONS
(in thylakoids)
NADPH
ATP
O2
An overview of the two stages ofphotosynthesis that take place in a chloroplastنظرة شاملة لمرحلتي البناء الضوئي التي تتم في الب!ستيدة الخضراء
7.5 Overview: The two stages of photosynthesis are linked by ATP and NADPH
� Actually, photosynthesis occurs in twotwotwotwo metabolic stagesFirst stageFirst stageFirst stageFirst stage
– One stage involves the light reactions– In the light reactionslight reactionslight reactionslight reactions, light energy is converted in the thylakoid membranes to chemical energy and O2
– Water is split to provide the O2 as well as electrons
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7.5 Overview: The two stages of photosynthesis are linked by ATP and NADPH
� H+ ions reduce NADP+ to NADPH, which is an electron carrier similar to NADH– NADPH is temporarily stored and then – NADPH is temporarily stored and then
shuttled into the Calvin cycle Calvin cycle Calvin cycle Calvin cycle where it is used to make sugar
– Finally, the light reactions generate ATP
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7.5 Overview: The two stages of photosynthesis are linked by ATP and NADPH
� The second stage is the Calvin cycleCalvin cycleCalvin cycleCalvin cycle, which occurs in the stroma of the chloroplast– It is a cyclic series of reactions that builds
Second stageSecond stageSecond stageSecond stage
– It is a cyclic series of reactions that builds sugar molecules from CO2 and the products of the light reactions– During the Calvin cycleCalvin cycleCalvin cycleCalvin cycle, CO2 is incorporated into organic compounds, a process called carbon fixationcarbon fixationcarbon fixationcarbon fixation
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7.5 Overview: The two stages of photosynthesis are linked by ATP and NADPH
NADHو ATPترتبط مرحلتي البناء الضوئي بـ : نظرة شاملة
� NADPH produced by the light reactions provides the electrons for reducing carbon in the Calvin cycle– ATP from the light reactions provides
chemical energy for the Calvin cycle– The Calvin cycle is often called the
dark (or light-independent) reactionsCopyright © 2009 Pearson Education, Inc.
H2O
ADPP
Lightضوء
Chloroplast ب!ستيدة خضراء
CALVINCYCLEدورة كالفين
CO2
NADP+
LIGHT REACTIONS
تفاع!ت الضوء
NADPH
ATP
O2
دورة كالفين(in stroma)
)في الحشوة(
Sugarسكر
An overview of the twostages of photosynthesis
that take place in a chloroplastنظرة شاملة لمرحلتي
ءالبناء الضوئي التي تتم في الب!ستيدة الخضرا
تفاع!ت الضوء
(in thylakoids))في القريصات(
PHOTOSYNTHESIS REVIEWED AND EXTENDED
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7.11 Review: Photosynthesis uses light energy, CO2, and H2O to make food molecules
� The chloroplast, which integrates the two stages of The chloroplast, which integrates the two stages of The chloroplast, which integrates the two stages of The chloroplast, which integrates the two stages of photosynthesis, makes sugar from COphotosynthesis, makes sugar from COphotosynthesis, makes sugar from COphotosynthesis, makes sugar from CO2222
– All but a few microscopic organisms depend on the food-making machinery of photosynthesisthe food-making machinery of photosynthesis
– Plants make more food than they actually need and stockpile it as starch as starch as starch as starch in rootsin rootsin rootsin roots, tuberstuberstuberstubers, and fruits
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NADP+
CO2
+
H2O
ADPP
Electrontransport
chains
LightChloroplast
CALVINCYCLE
(in stroma)
Photosystem IIRuBP
3-PGA
Summary of the chemicalprocesses of photosynthesis
NADPH
ATP
chains
ThylakoidMembranes
O2Sugars
Photosystem I
LIGHT REACTIONS CALVIN CYCLE
Stroma
G3P Cellularrespiration
CelluloseStarchOther organiccompounds
PHOTOSYNTHESIS, SOLAR RADIATION,
AND EARTH’S ATMOSPHEREAND EARTH’S ATMOSPHERE
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7.13 CONNECTION: Photosynthesis moderates global warming
� The greenhouse effectgreenhouse effectgreenhouse effectgreenhouse effect results from solar energy warming our planet– Gases in the atmosphere (often called
greenhouse gases), including CO2, reflect heat back to Earth, keeping the planet warm and greenhouse gases), including CO2, reflect heat back to Earth, keeping the planet warm and supporting life
– However, as we increase the level of greenhouse gases, Earth’s temperature rises above normal, initiating problems
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7.13 CONNECTION: Photosynthesis moderates global warming
� Increasing concentrations of greenhouse gases lead to global warmingglobal warmingglobal warmingglobal warming, a slow but steady rise in Earth’s surface temperature– The extraordinary rise in CO2 is mostly due to the
combustion of carbon-based fossil fuelscombustion of carbon-based fossil fuels– The consequences of continued rise will be melting of
polar ice, changing weather patterns, and spread of tropical disease
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7.13 CONNECTION: Photosynthesis moderates global warming
� Perhaps photosynthesis can mitigate the increase in atmospheric CO2
– However, there is increasing widespread deforestation, which aggravates the global warming problem
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Plants growing in a greenhouse
Atmosphere
Sunlight
Some heatenergy escapes
into space
Radiant heattrapped by CO 2trapped by CO 2and other gases
CO2 in the atmosphere and global warming
Diffusion: is a process in which particles spread out evenly in an available space
ھو عملية شيوع الجزيئات بالتساوي في فراغ �نتشارامتاح
Selectively permeability: allow some substances to cross or be transported more easily than others
وذلك بسماحھا بسھولة مرور خاصية النفاذ التفاضليةونقل بعض المواد فض&ً عن غيرھا
Concentration gradient: from high concentration to low concentration
من مناطق التركيز العالي إلى مناطق مدرج التركيزالتركيز المنخفض
Passive transport: is theDiffusion across a cell membrane without
ھو ا>نتشار خ&ل غشاء الخلية بدون ا�نتقال السلبيالحاجة إلى طاقة
المصطلح تعريف المصطلح
The Working Cell الخلية العاملة
Diffusion across a cell membrane without energyActive transport: a mechanism for moving a solute against its concentration gradient it requires the expenditure of energy in the form of ATP.
الخ&يا آلية لتحريك المذاب عكس اتجاه مدرج النقل النشط .ATPالتركيز يحتاج ذلك لبذل الطاقة على ھيئة الـ
Osmosis: the Water movement across membranes in response to solute concentration inside and outside of the cell down the concentration gradient.
ھي يتحرك الماء عبر اLغشية استجابة لتركيز ا+سموزيةمدرج التركيز اسفلالمذاب داخل وخارج الخلية تجاه
Tonicity: is a term that describes the ability of a solution to cause a cell to gain or lose water
مصطلح يصف مقدرة المحلول على إكساب أو فقد التوترالخلية للماء
المصطلح تعريف المصطلح
The Working Cell الخلية العاملة
Osmoregulation: is the ablilty of organisms to maintain water balance within their cells
ھي خاصية لدى بعض الحيوانات ا+سموزيالتنظيم المائي داخل خ&ياھا إتزانھاالحفاظ على
facilitated diffusion: a type of passive transport that does not require energy
طقةنوع من النقل السلبي الذي W يحتاج ا�نتشار الُمَدعم
Exocytosis: is used to export bulky moleculesout of the cell
آلية لتصدير الجزيئات الضخمة خارج الطرد الخلويالخلية
Endocytosis: is used to import substances useful to the livelihood of the cell
آلية لتوريد مواد نافعة لمعيشة الخلية إلى ا�بت5ع الخلويداخل الخلية useful to the livelihood of the cellداخل الخلية
Phagocytosis: engulfment of a particle by wrapping cell membrane around it, forming a vacuole
ھو ابت&ع الجزيئات بتغليفھا الخلوي ا;لتھامأو البلعمةبغشاء الخلية مكونة فجوة
Pinocytosis: the same as phagocytosis except that fluids are taken into small vesicles
إW أن السوائل ھي البلعمةعبارة عن نفس الشرب الخلويالتي تؤخذ في حويص&ت صغيرة
Cells:small units, a chemical factory, housing thousands of chemical reactions
وحدات صغيرة ھي بمثابة مصانع كيميائية تحتضن الخ5يا آWف التفاع&ت الكيميائية
Energy: is the capacity to do work and cause change
ھي القدرة على عمل شغل >حداث تغيير لطاقةا
المصطلح تعريف المصطلح
The Working Cell الخلية العاملة
A metabolic pathway: is a series of chemical reactions that either break down a complex molecule or build up a complex molecule
عبارة عن سلسلة من التفاع&ت الكيميائية المسار ا+يضيوالتي إما تھدم أو تبني جزيء معقد
Energy coupling: it is the use of exergonic processes to drive an endergonic one
استخدام التفاع&ت المحررة للطاقة >مداد إقران الطاقةللطاقة بما تحتاجه من الطاقة المستقبلهالتفاع&ت
ATP( adenosine triphosphate): the energy currency of cells and it is the immediate source of energy that powers most forms of
الطاقة في ” ُعملة“ھو ATP)( ا+دينوسينث5ثي فوسفات ھو مصدر الطاقة الفوري الذي يزود ATP والخلية
source of energy that powers most forms ofمعظم أشكال الشغل الخلوي بالطاقة cellular work
معظم أشكال الشغل الخلوي بالطاقة
Active site: where the enzyme interacts with the enzyme’s substrate
حيث يتفاعل ا>نزيم مع عامل ا>نزيم منطقة نشطةالخاص به
Cofactors: inorganic enzymes helpers ھي مواد غير عضوية مساعدة العوامل المرافقةلeنزيمات
Coenzymes: organic enzymes helpers ھي جزيئات عضوية مساعدة مرافقات ا;نزيماتلeنزيمات
Competitive inhibitors: inhibits enzymes because they compete for the enzyme’s active site and thus block substrates from entering the active site
تقوم بالتثبيط Lنھا تستبق نحو الموقع المثبطات التنافسيةالنشط في ا>نزيم وبالتالي تحجب عامله من دخول ذلك
الموقع
المصطلح تعريف المصطلح
The Working Cell الخلية العاملة
Non competitive inhibitors: bind somewhere else and change the shape of the enzyme so that the substrate will no longer fit the active site
ترتبط ھذه المثبطات بمكان آخر المثبطات غير التنافسيةمغيره شكله ف& يصبح الموقع النشط مناسباً اWنزيممن
اWنزيملعامل
Feedback inhibition: a mechanism where the product of a metabolic pathway can serve as an inhibitor of one enzyme in the pathway
آيضيحيث يعمل أحد نواتج مسار بالتثبيط الرجعي اGليةكمثبط Lحد ا>نزيمات في ذلك المسار
Cellular respiration: an exergonic process ھو عملية تفاعل محرر للطاقة والتي التنفس الخلويCellular respiration: an exergonic process that transfers energy from the bonds in glucose to ATP
ھو عملية تفاعل محرر للطاقة والتي التنفس الخلويتحرر الطاقة المختزنة في روابط جزيء الجلوكوز
ATPوتخزينھا فيA kilocalorie (kcal): the quantity of heat required to raise the temperature of 1 kilogram (kg) of water by 1oC
ھي كمية الحرارة )كالوريكيلو (الحرارية السعرةكيلوجرام من الماء درجة 1المطلوبة لرفع درجة حرارة
) م°ا (مئوية واحدة Dehydrogenase: the enzyme that removes hydrogen from an organic molecule
ا>نزيم الذي )نزع الھيدروجين انزيم( الديھايدروجينيزيزيل الھيدروجين من الجزيء العضوي
NAD+(nicotinamide adenine dinucleotide): a shuttle for electrons
NAD+ )ناقل :)ا+دنين نيكوتين أميد الثنائية نيوكليتيدة&لكتروناتل
Glycolysis تحلل الجلوكوز The citric acid cycle الستريكدورة حامض
المصطلح تعريف المصطلح
The Working Cell الخلية العاملة
Oxidative phosphorylation المؤكِسدة الفسفرةFermentation: an anaerobic (without oxygen) energy-generating process
دون الحاجة (ھو عملية توليد الطاقة W ھوائيا التخمر) Lوكسجين
lactic acid fermentation: oxidizing of NADH by muscle cells and bacteria
تؤكسد الخ&يا العضلية وبعض تخمر الحامض اللبنيNADH الـأنواع البكتيريا مركب
Yeasts: single-celled fungi that not only can use respiration for energy but can ferment under anaerobic conditions
انھاجانب الىھي فطريات وحيدة الخلية ، لخمائرا>نتاج الطاقة فھي ) ھوائيا(تستطيع القيام بالتنفس الخلوي
ال&ھوائيةقادرة على القيام بعملية التخمر تحت الظروف Autotrophs: living things that are able to ھي كائنات حية قادرة على تصنيع الكائنات ذاتية التغذيةAutotrophs: living things that are able to make their own food without using organic molecules derived from any other living thing
ھي كائنات حية قادرة على تصنيع الكائنات ذاتية التغذيةغذائھا دون استخدام جزيئات عضوية مستمدة من أي كائن
حي آخر
Photoautotrophs: the use of energy of light to produce organic molecules by Autotrophs
استخدم طاقة الضوء >نتاج جزيئات التغذية الضوئيةعضوية بالكائنات ذاتية
Chloroplasts: organelles consisting of photosynthetic pigments, enzymes, and other molecules grouped together in membranes
ھي عضيات تتكون من صبغات الب5ستيدات الخضراءمكونة للضوء وإنزيمات ومركبات أخرى مجموعة مع
بعضھا البعض في أغشية Chlorophyll: an important light absorbing pigment in chloroplasts, is responsible for the green color of plants
الب&ستيداتصبغة ھامة Wمتصاص الضوء في الكلوروفيل افي النبات اWخضرالخضراء وھي المسئولة عن اللون