Photosynthesis: Using Light to Make Food

Photosynthesis: Using Light to Make Food
Chapter 7 Photosynthesis: Using Light to Make Food Lecture by Richard L. Myers Translated 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 photosynthesis, a process that converts solar energy to chemical energy Sugar is food for humans and for animals that we consume Carbon dioxide C6H12O6 Photosynthesis H2O CO2 O2 Water + 6 6 Light energy Oxygen gas Glucose + 6 Photosynthesis nourishes almost the entire living world directly or indirectly. Almost all plants are autotrophs, meaning that they sustain themselves without eating anything derived from other living beings. Plants produce oxygen, a by-product of photosynthesis, that is used in respiration. The solar energy used in photosynthesis traveled 150 million kilometers from the sun to Earth to be converted into chemical energy. You may want to reintroduce the terms producers and consumers within the context of this chapter.

AN OVERVIEW OF PHOTOSYNTHESIS
Copyright © 2009 Pearson Education, Inc.

7.1 Autotrophs are the producers of the biosphere
Autotrophs 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 photoautotrophs Most plants, algae and other protists, and some prokaryotes are photoautotrophs A very interesting class of autotrophs are the autotrophic bacteria that use carbon dioxide to synthesize organic molecules without solar energy. Teaching Tips 1. When introducing the diverse ways that plants impact our lives, consider challenging your students to come up with a list of products made from plants that they come across on a regular basis. The collective lists from your students can be surprisingly long and might help to build up your catalog of examples. 2. The evolution of chloroplasts from photosynthetic prokaryotes living inside of eukaryotic cells is briefly noted in a reference to Module If your students have not already read Chapter 4, consider discussing the evidence that suggests this endosymbiotic origin. 3. Some students might think that the term producers applies to the production of oxygen by plants. In turn, they might think that consumers are organisms that use oxygen (which would include all aerobic organisms). Extra care may be needed to clarify the definitions of these frequently used terms. Kelp, a large algaeالكيلب طحلب كبير Copyright © 2009 Pearson Education, Inc.

7.1 Autotrophs are the producers of the biosphere
The ability to photosynthesize is directly related to the structure of chloroplasts Chloroplasts are organelles consisting of photosynthetic pigments, enzymes, and other molecules grouped together in membranes There are about half a million chloroplasts per square millimeter of leaf surface. Chloroplast membranes are similar to mitochondrial membranes in that both are important in energy-harvesting duties of the cell. Teaching Tips 1. When introducing the diverse ways that plants impact our lives, consider challenging your students to come up with a list of products made from plants that they come across on a regular basis. The collective lists from your students can be surprisingly long and might help to build up your catalog of examples. 2. The evolution of chloroplasts from photosynthetic prokaryotes living inside of eukaryotic cells is briefly noted in a reference to Module If your students have not already read Chapter 4, consider discussing the evidence that suggests this endosymbiotic origin. 3. Some students might think that the term producers applies to the production of oxygen by plants. In turn, they might think that consumers are organisms that use oxygen (which would include all aerobic organisms). Extra care may be needed to clarify the definitions of these frequently used terms. Micrograph of cyanobacteria (photosynthetic bacteria) ) Copyright © 2009 Pearson Education, Inc.

7.2 Photosynthesis occurs in chloroplasts in plant cells
Chloroplasts are the major sites of photosynthesis in green plants Chlorophyll, an important light absorbing pigment in chloroplasts, is responsible for the green color of plants Chlorophyll plays a central role in converting solar energy to chemical energy Chlorophyll absorbs light energy and drives the synthesis of organic molecules. Teaching Tips 1. The authors note the analogous roles of the thylakoid space and the intermembrane space of a mitochondrion. Students might be encouraged to create a list of the similarities in structure and function of mitochondria and chloroplasts through these related chapters. 2. The living world contains many examples of adaptations to increase surface area. Some examples are the many folds of the inner mitochondrial membrane, the highly branched surfaces of fish gills and human lungs, and the highly branched system of capillaries in the tissues of our bodies. Consider relating this broad principle to the extensive folding of the thylakoid membranes. Copyright © 2009 Pearson Education, Inc.

CO2 O2 Stoma Mesophyll Cell Vein Chloroplast Mesophyll Leaf Cross Section Figure 7.2 The location and structure of chloroplasts. The location and structure of chloroplasts

Chloroplasts are concentrated in the cells of the mesophyll, the green tissue in the interior of the leaf Stomata are tiny pores in the leaf that allow carbon dioxide to enter and oxygen to exit Veins in the leaf deliver water absorbed by roots Leaves also use veins to export sugar to roots and other nonphotosynthetic parts of the plant. Teaching Tips 1. The authors note the analogous roles of the thylakoid space and the intermembrane space of a mitochondrion. Students might be encouraged to create a list of the similarities in structure and function of mitochondria and chloroplasts through these related chapters. 2. The living world contains many examples of adaptations to increase surface area. Some examples are the many folds of the inner mitochondrial membrane, the highly branched surfaces of fish gills and human lungs, and the highly branched system of capillaries in the tissues of our bodies. Consider relating this broad principle to the extensive folding of the thylakoid membranes. Copyright © 2009 Pearson Education, Inc.

Chloroplast Outer and inner membranes Intermembrane space Thylakoid
Stroma Granum Thylakoid Space Figure 7.2 The location and structure of chloroplasts.

An envelope of two membranes encloses the stroma, the dense fluid within the chloroplast A system of interconnected membranous sacs called thylakoids segregates the stroma from another compartment, the thylakoid space Thylakoids are concentrated in stacks called granam Chlorophyll resides in the thylakoid membranes. Teaching Tips 1. The authors note the analogous roles of the thylakoid space and the intermembrane space of a mitochondrion. Students might be encouraged to create a list of the similarities in structure and function of mitochondria and chloroplasts through these related chapters. 2. The living world contains many examples of adaptations to increase surface area. Some examples are the many folds of the inner mitochondrial membrane, the highly branched surfaces of fish gills and human lungs, and the highly branched system of capillaries in the tissues of our bodies. Consider relating this broad principle to the extensive folding of the thylakoid membranes. Copyright © 2009 Pearson Education, Inc.

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 experiments that O2 actually comes from H2O C. B. van Niel of Stanford University hypothesized that plants split water into hydrogen and oxygen. His hypothesis was confirmed 20 years later. A significant result of photosynthesis is the extraction of hydrogen from water and its incorporation into sugar. Oxygen is a waste product of photosynthesis. The chloroplast is the site where water is split into hydrogen and oxygen. Student Misconceptions and Concerns 1. Students may not connect the growth in plant mass to the fixation of carbon during the Calvin cycle. It can be difficult for many students to appreciate that molecules in air can contribute significantly to the mass of plants. Teaching Tips 1. Many students do not realize that glucose is not the direct product of photosynthesis. The authors note that although glucose is shown as a product of photosynthesis, a three-carbon sugar is directly produced (G3P). A plant can use G3P to make many types of organic molecules, including glucose. Oxygen bubbles on the leaves of an aquatic plant Copyright © 2009 Pearson Education, Inc.

Experiments tracking the oxygen atoms in photosynthesis
6 CO H2O C6H12O H2O O2 Not labeled Experiment 2 6 CO H2O C6H12O H2O O2 Figure 7.3B Experiments tracking the oxygen atoms in photosynthesis. Labeled Experiments tracking the oxygen atoms in photosynthesis

Fates of all the atoms in photosynthesis
Reactants: 6 CO2 12 H2O Products: C6H12O6 6 H2O 6 O2 Figure 7.3C Fates of all the atoms in photosynthesis.

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 electrons along with hydrogen ions (H+) Then CO2 is reduced to sugar as electrons and hydrogen ions are added to it The simple sugar produced in photosynthesis is glucose, using a number of energy-releasing redox reactions. Teaching Tips 1. In our world, energy is frequently converted to a usable form in one place and used in another. For example, electricity is generated by power plants, transferred to our homes, and used to run computers, create light, and help us prepare foods. Consider relating this common energy transfer to the two-stage process of photosynthesis. Copyright © 2009 Pearson Education, Inc.

6 CO2 + 6 H2O Reduction Oxidation C6H12O6 + 6 O2 Reduction Oxidation
Photosynthesis (uses light energy) 6 CO H2O C6H12O O2 Reduction Oxidation Cellular respiration (releases chemical energy) Figure 7.4B Cellular respiration (releases chemical energy). 6 CO H2O + E C6H12O O2 Reduction Oxidation

7.4 Photosynthesis is a redox process, as is cellular respiration
Recall that cellular respiration uses redox reactions to harvest the chemical energy stored in a glucose molecule This is accomplished by oxidizing the sugar and reducing 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 In respiration, mitochondria harness chemical energy to synthesize ATP. In photosynthesis, the energy boost is provided by light and occurs in chloroplasts. Eventually, ATP is synthesized. Teaching Tips 1. In our world, energy is frequently converted to a usable form in one place and used in another. For example, electricity is generated by power plants, transferred to our homes, and used to run computers, create light, and help us prepare foods. Consider relating this common energy transfer to the two-stage process of photosynthesis. Copyright © 2009 Pearson Education, Inc.

An overview of the two stages of
H2O Chloroplast Light NADP+ ADP  P LIGHT REACTIONS (in thylakoids) Figure 7.5 An overview of the two stages of photosynthesis that take place in a chloroplast. Figure 7.5 is an important visual organizer that notes the key structures and functions of the two stages of photosynthesis. This figure reminds students where water and sunlight are used in the thylakoid membranes to generate oxygen, ATP, and NADPH. The second step, in the stroma, reveals the use of carbon dioxide, ATP, and NADPH to generate carbohydrates. An overview of the two stages of photosynthesis that take place in a chloroplast

اليكترونات H2O Chloroplastبلاستيدة خضراء Light ضوء NADP+ ADP  P LIGHT
REACTIONS (in thylakoids) ATP Figure 7.5 An overview of the two stages of photosynthesis that take place in a chloroplast. Figure 7.5 is an important visual organizer that notes the key structures and functions of the two stages of photosynthesis. This figure reminds students where water and sunlight are used in the thylakoid membranes to generate oxygen, ATP, and NADPH. The second step, in the stroma, reveals the use of carbon dioxide, ATP, and NADPH to generate carbohydrates. Electrons اليكترونات NADPH An overview of the two stages of photosynthesis that take place in a chloroplast نظرة شاملة لمرحلتي البناء الضوئي التي تتم في البلاستيدة الخضراء O2

7.5 Overview: The two stages of photosynthesis are linked by ATP and NADPH
Actually, photosynthesis occurs in two metabolic stages First stage One stage involves the light reactions In the light 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 The two metabolic stages are the light reactions and the Calvin cycle. Student Misconceptions and Concerns 1. Students may understand the overall chemical relationships between photosynthesis and cellular respiration, but many struggle to understand the use of carbon dioxide in the Calvin cycle. Photosynthesis is much more than gas exchange. Teaching Tips 1. In our world, energy is frequently converted to a usable form in one place and used in another. For example, electricity is generated by power plants, transferred to our homes, and used to run computers, create light, and help us prepare foods. Consider relating this common energy transfer to the two-stage process of photosynthesis. 2. Figure 7.5 is an important visual organizer that notes the key structures and functions of the two stages of photosynthesis. This figure demonstrates where water and sunlight are used in the thylakoid membranes to generate oxygen, ATP, and NADPH. The second step, in the stroma, reveals the use of carbon dioxide, ATP, and NADPH to generate carbohydrates. Copyright © 2009 Pearson Education, Inc.

Finally, the light reactions generate ATP
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 shuttled into the Calvin cycle where it is used to make sugar Finally, the light reactions generate ATP Catabolic processes like cellular respiration generally use NAD+ as the initial hydrogen acceptor, while anabolic reactions, such as photosynthesis, use NADP+. Sugar is not produced in the light reactions; it is not produced until the Calvin cycle, the second stage of photosynthesis. Student Misconceptions and Concerns 1. Students may understand the overall chemical relationships between photosynthesis and cellular respiration, but many struggle to understand the use of carbon dioxide in the Calvin cycle. Photosynthesis is much more than gas exchange. Teaching Tips 1. In our world, energy is frequently converted to a usable form in one place and used in another. For example, electricity is generated by power plants, transferred to our homes, and used to run computers, create light, and help us prepare foods. Consider relating this common energy transfer to the two-stage process of photosynthesis. 2. Figure 7.5 is an important visual organizer that notes the key structures and functions of the two stages of photosynthesis. This figure demonstrates where water and sunlight are used in the thylakoid membranes to generate oxygen, ATP, and NADPH. The second step, in the stroma, reveals the use of carbon dioxide, ATP, and NADPH to generate carbohydrates. Copyright © 2009 Pearson Education, Inc.

7.5 Overview: The two stages of photosynthesis are linked by ATP and NADPH
Second stage The second stage is the Calvin cycle, which occurs in the stroma of the chloroplast It is a cyclic series of reactions that builds sugar molecules from CO2 and the products of the light reactions During the Calvin cycle, CO2 is incorporated into organic compounds, a process called carbon fixation The Calvin cycle was named for the Nobel laureate, Melvin Calvin, who traced the path of carbon in the cycle. Student Misconceptions and Concerns 1. Students may understand the overall chemical relationships between photosynthesis and cellular respiration, but many struggle to understand the use of carbon dioxide in the Calvin cycle. Photosynthesis is much more than gas exchange. Teaching Tips 1. In our world, energy is frequently converted to a usable form in one place and used in another. For example, electricity is generated by power plants, transferred to our homes, and used to run computers, create light, and help us prepare foods. Consider relating this common energy transfer to the two-stage process of photosynthesis. 2. Figure 7.5 is an important visual organizer that notes the key structures and functions of the two stages of photosynthesis. This figure demonstrates where water and sunlight are used in the thylakoid membranes to generate oxygen, ATP, and NADPH. The second step, in the stroma, reveals the use of carbon dioxide, ATP, and NADPH to generate carbohydrates. Copyright © 2009 Pearson Education, Inc.

7.5 Overview: The two stages of photosynthesis are linked by ATP and NADPH نظرة شاملة : ترتبط مرحلتي البناء الضوئي بـ ATP و NADH 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) reactions The Calvin cycle occurs during daytime in most plants when the light reactions are powering the cycle’s sugar assembly line. For the BioFlix Animation Photosynthesis, go to Animation and Video Files. For the Discovery Video Trees, go to Animation and Video Files. Student Misconceptions and Concerns 1. Students may understand the overall chemical relationships between photosynthesis and cellular respiration, but many struggle to understand the use of carbon dioxide in the Calvin cycle. Photosynthesis is much more than gas exchange. Teaching Tips 1. In our world, energy is frequently converted to a usable form in one place and used in another. For example, electricity is generated by power plants, transferred to our homes, and used to run computers, create light, and help us prepare foods. Consider relating this common energy transfer to the two-stage process of photosynthesis. 2. Figure 7.5 is an important visual organizer that notes the key structures and functions of the two stages of photosynthesis. This figure demonstrates where water and sunlight are used in the thylakoid membranes to generate oxygen, ATP, and NADPH. The second step, in the stroma, reveals the use of carbon dioxide, ATP, and NADPH to generate carbohydrates. Copyright © 2009 Pearson Education, Inc.

اليكترونات H2O CO2 Chloroplastبلاستيدة خضراء Light ضوء NADP+ ADP  P
REACTIONS تفاعلات الضوء CALVIN CYCLE دورة كالفين (in thylakoids) (في القريصات) (in stroma) (في الحشوة) ATP Figure 7.5 An overview of the two stages of photosynthesis that take place in a chloroplast. Figure 7.5 is an important visual organizer that notes the key structures and functions of the two stages of photosynthesis. This figure reminds students where water and sunlight are used in the thylakoid membranes to generate oxygen, ATP, and NADPH. The second step, in the stroma, reveals the use of carbon dioxide, ATP, and NADPH to generate carbohydrates. Electrons اليكترونات NADPH An overview of the two stages of photosynthesis that take place in a chloroplast نظرة شاملة لمرحلتي البناء الضوئي التي تتم في البلاستيدة الخضراء Sugar سكر O2

PHOTOSYNTHESIS REVIEWED AND EXTENDED

7.11 Review: Photosynthesis uses light energy, CO2, and H2O to make food molecules
The chloroplast, which integrates the two stages of photosynthesis, makes sugar from CO2 All but a few microscopic organisms depend on the food-making machinery of photosynthesis Plants make more food than they actually need and stockpile it as starch in roots, tubers, and fruits Although photosynthesizers produce sugar for self-consumption, their sugar is a source for virtually all other organisms on Earth. Student Misconceptions and Concerns 1. Some students do not realize that plant cells also have mitochondria. Instead, they assume that the chloroplasts are sufficient for the plant cell’s needs. As noted in the text, nearly 50% of the carbohydrates produced by plant cells are used for cellular respiration (involving mitochondria). Teaching Tips 1. Challenge students to explain how the energy in beef is ultimately derived from the sun. 2. The authors note that G3P is also used to produce cellulose, the most abundant compound on Earth. Each year, plants produce about 100 billion tons of cellulose! Copyright © 2009 Pearson Education, Inc.

Summary of the chemical processes of photosynthesis
CO2 Chloroplast Light NADP+ ADP + P Photosystem II CALVIN CYCLE RuBP Electron transport chains (in stroma) 3-PGA Thylakoid Membranes Photosystem I ATP Stroma Figure 7.11 A summary of the chemical processes of photosynthesis. NADPH G3P Cellular respiration Cellulose Starch O2 Sugars Other organic compounds LIGHT REACTIONS CALVIN CYCLE

PHOTOSYNTHESIS, SOLAR RADIATION, AND EARTH’S ATMOSPHERE

7.13 CONNECTION: Photosynthesis moderates global warming
The greenhouse 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 supporting life However, as we increase the level of greenhouse gases, Earth’s temperature rises above normal, initiating problems Student Misconceptions and Concerns 1. Students may confuse global warming with the breakdown of the ozone layer. Be prepared to explain both phenomena and the impact of human activities. 2. Students often do not fully understand how the burning of fossil fuels contributes to global warming. They might wonder, “How does the burning of fossil fuels differ from the burning of ethanol produced from crops?” Students might not realize that the carbon in fossil fuels was removed from the atmosphere hundreds of millions of years ago, while the carbon in crops was removed much more recently, when the crops were grown. Teaching Tips 1. Some students might better relate the greenhouse effect to what happens inside their closed car on a sunny day. The glass in our automobiles functions just like the glass of a greenhouse, trapping heat inside our car. This can be an advantage during the winter but is usually not welcome on a hot summer day! Copyright © 2009 Pearson Education, Inc.

Increasing concentrations of greenhouse gases lead to global 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 fuels The consequences of continued rise will be melting of polar ice, changing weather patterns, and spread of tropical disease Student Misconceptions and Concerns 1. Students may confuse global warming with the breakdown of the ozone layer. Be prepared to explain both phenomena and the impact of human activities. 2. Students often do not fully understand how the burning of fossil fuels contributes to global warming. They might wonder, “How does the burning of fossil fuels differ from the burning of ethanol produced from crops?” Students might not realize that the carbon in fossil fuels was removed from the atmosphere hundreds of millions of years ago, while the carbon in crops was removed much more recently, when the crops were grown. Teaching Tips 1. Some students might better relate the greenhouse effect to what happens inside their closed car on a sunny day. The glass in our automobiles functions just like the glass of a greenhouse, trapping heat inside our car. This can be an advantage during the winter but is usually not welcome on a hot summer day! Copyright © 2009 Pearson Education, Inc.

Perhaps photosynthesis can mitigate the increase in atmospheric CO2 However, there is increasing widespread deforestation, which aggravates the global warming problem Student Misconceptions and Concerns 1. Students may confuse global warming with the breakdown of the ozone layer. Be prepared to explain both phenomena and the impact of human activities. 2. Students often do not fully understand how the burning of fossil fuels contributes to global warming. They might wonder, “How does the burning of fossil fuels differ from the burning of ethanol produced from crops?” Students might not realize that the carbon in fossil fuels was removed from the atmosphere hundreds of millions of years ago, while the carbon in crops was removed much more recently, when the crops were grown. Teaching Tips 1. Some students might better relate the greenhouse effect to what happens inside their closed car on a sunny day. The glass in our automobiles functions just like the glass of a greenhouse, trapping heat inside our car. This can be an advantage during the winter but is usually not welcome on a hot summer day! Copyright © 2009 Pearson Education, Inc.

Plants growing in a greenhouse
Figure 7.13A Plants growing in a greenhouse. Plants growing in a greenhouse

CO2 in the atmosphere and global warming
Some heat energy escapes into space Sunlight Atmosphere Radiant heat trapped by CO2 and other gases Figure 7.13B CO2 in the atmosphere and global warming. CO2 in the atmosphere and global warming

The Working Cellالخلية العاملة
المصطلح تعريف المصطلح Diffusion: is a process in which particles spread out evenly in an available space الانتشار هو عملية شيوع الجزيئات بالتساوي في فراغ متاح Selectively permeability: allow some substances to cross or be transported more easily than others خاصية النفاذ التفاضلية وذلك بسماحها بسهولة مرور ونقل بعض المواد فضلاً عن غيرها Concentration gradient: from high concentration to low concentration مدرج التركيز من مناطق التركيز العالي إلى مناطق التركيز المنخفض Passive transport: is the Diffusion across a cell membrane without energy الانتقال السلبي هو الإنتشار خلال غشاء الخلية بدون الحاجة إلى طاقة Active transport: a mechanism for moving a solute against its concentration gradient it requires the expenditure of energy in the form of ATP. النقل النشط الخلايا آلية لتحريك المذاب عكس اتجاه مدرج التركيز يحتاج ذلك لبذل الطاقة على هيئة الـ ATP. Osmosis: the Water movement across membranes in response to solute concentration inside and outside of the cell down the concentration gradient. الأسموزية هي يتحرك الماء عبر الأغشية استجابة لتركيز المذاب داخل وخارج الخلية تجاه اسفل مدرج التركيز Tonicity: is a term that describes the ability of a solution to cause a cell to gain or lose water التوتر مصطلح يصف مقدرة المحلول على إكساب أو فقد الخلية للماء

المصطلح تعريف المصطلح Osmoregulation: is the ablilty of organisms to maintain water balance within their cells التنظيم الأسموزي هي خاصية لدى بعض الحيوانات الحفاظ على إتزانها المائي داخل خلاياها facilitated diffusion: a type of passive transport that does not require energy الانتشار المُدَعم نوع من النقل السلبي الذي لا يحتاج طقة Exocytosis: is used to export bulky moleculesout of the cell الطرد الخلوي آلية لتصدير الجزيئات الضخمة خارج الخلية Endocytosis: is used to import substances useful to the livelihood of the cell الابتلاع الخلوي آلية لتوريد مواد نافعة لمعيشة الخلية إلى داخل الخلية Phagocytosis: engulfment of a particle by wrapping cell membrane around it, forming a vacuole البلعمة أو الإلتهام الخلوي هو ابتلاع الجزيئات بتغليفها بغشاء الخلية مكونة فجوة Pinocytosis: the same as phagocytosis except that fluids are taken into small vesicles الشرب الخلوي عبارة عن نفس البلعمة إلا أن السوائل هي التي تؤخذ في حويصلات صغيرة Cells: small units, a chemical factory, housing thousands of chemical reactions الخلايا وحدات صغيرة هي بمثابة مصانع كيميائية تحتضن آلاف التفاعلات الكيميائية Energy: is the capacity to do work and cause change الطاقة هي القدرة على عمل شغل لإحداث تغيير

المصطلح تعريف المصطلح A metabolic pathway: is a series of chemical reactions that either break down a complex molecule or build up a complex molecule المسار الأيضي عبارة عن سلسلة من التفاعلات الكيميائية والتي إما تهدم أو تبني جزيء معقد Energy coupling: it is the use of exergonic processes to drive an endergonic one إقران الطاقة استخدام التفاعلات المحررة للطاقة لإمداد التفاعلات المستقبله للطاقة بما تحتاجه من الطاقة ATP( adenosine triphosphate): the energy currency of cells and it is the immediate source of energy that powers most forms of cellular work ثلاثي فوسفات الأدينوسين ((ATP هو ”عُملة“ الطاقة في الخلية و ATP هو مصدر الطاقة الفوري الذي يزود معظم أشكال الشغل الخلوي بالطاقة Active site: where the enzyme interacts with the enzyme’s substrate منطقة نشطة حيث يتفاعل الإنزيم مع عامل الإنزيم الخاص به Cofactors: inorganic enzymes helpers العوامل المرافقة هي مواد غير عضوية مساعدة للإنزيمات Coenzymes: organic enzymes helpers مرافقات الإنزيمات هي جزيئات عضوية مساعدة للإنزيمات Competitive inhibitors: inhibits enzymes because they compete for the enzyme’s active site and thus block substrates from entering the active site المثبطات التنافسية تقوم بالتثبيط لأنها تستبق نحو الموقع النشط في الإنزيم وبالتالي تحجب عامله من دخول ذلك الموقع

المصطلح تعريف المصطلح Non competitive inhibitors: bind somewhere else and change the shape of the enzyme so that the substrate will no longer fit the active site المثبطات غير التنافسية ترتبط هذه المثبطات بمكان آخر من الانزيم مغيره شكله فلا يصبح الموقع النشط مناسباً لعامل الانزيم Feedback inhibition: a mechanism where the product of a metabolic pathway can serve as an inhibitor of one enzyme in the pathway بالتثبيط الرجعي الآلية حيث يعمل أحد نواتج مسار آيضي كمثبط لأحد الإنزيمات في ذلك المسار Cellular respiration: an exergonic process that transfers energy from the bonds in glucose to ATP التنفس الخلوي هو عملية تفاعل محرر للطاقة والتي تحرر الطاقة المختزنة في روابط جزيء الجلوكوز وتخزينها فيATP A kilocalorie (kcal): the quantity of heat required to raise the temperature of 1 kilogram (kg) of water by 1oC السعرة الحرارية (كيلو كالوري) هي كمية الحرارة المطلوبة لرفع درجة حرارة 1 كيلوجرام من الماء درجة مئوية واحدة (ا °م) Dehydrogenase: the enzyme that removes hydrogen from an organic molecule الديهايدروجينيز (انزيم نزع الهيدروجين( الإنزيم الذي يزيل الهيدروجين من الجزيء العضوي NAD+(nicotinamide adenine dinucleotide): a shuttle for electrons NAD+ (نيوكليتيدة الأدنين نيكوتين أميد الثنائية): ناقل للالكترونات Glycolysis تحلل الجلوكوز The citric acid cycle دورة حامض الستريك

المصطلح تعريف المصطلح Oxidative phosphorylation الفسفرة المؤكسِدة Fermentation: an anaerobic (without oxygen) energy-generating process التخمر هو عملية توليد الطاقة لا هوائيا (دون الحاجة لأوكسجين) lactic acid fermentation: oxidizing of NADH by muscle cells and bacteria تخمر الحامض اللبني تؤكسد الخلايا العضلية وبعض أنواع البكتيريا مركب الـ NADH Yeasts: single-celled fungi that not only can use respiration for energy but can ferment under anaerobic conditions الخمائر هي فطريات وحيدة الخلية ، الى جانب انها تستطيع القيام بالتنفس الخلوي (هوائيا) لإنتاج الطاقة فهي قادرة على القيام بعملية التخمر تحت الظروف اللاهوائية Autotrophs: living things that are able to make their own food without using organic molecules derived from any other living thing الكائنات ذاتية التغذية هي كائنات حية قادرة على تصنيع غذائها دون استخدام جزيئات عضوية مستمدة من أي كائن حي آخر Photoautotrophs: the use of energy of light to produce organic molecules by Autotrophs التغذية الضوئية استخدم طاقة الضوء لإنتاج جزيئات عضوية بالكائنات ذاتية Chloroplasts: organelles consisting of photosynthetic pigments, enzymes, and other molecules grouped together in membranes البلاستيدات الخضراء هي عضيات تتكون من صبغات مكونة للضوء وإنزيمات ومركبات أخرى مجموعة مع بعضها البعض في أغشية Chlorophyll: an important light absorbing pigment in chloroplasts, is responsible for the green color of plants الكلوروفيل صبغة هامة لامتصاص الضوء في البلاستيدات الخضراء وهي المسئولة عن اللون الاخضر في النبات ا

Photosynthesis: Using Light to Make Food

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Photosynthesis: Using Light to Make Food

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