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生物课英语作文As I embarked on the adventure of learning biology through the English language, I was immediately captivated by the fusion of scientific inquiry and linguistic expression. Biology, the study of life and living organisms, offers a window into the intricate tapestry of nature's design, while English, a versatile and widely spoken language, provides the tools to articulate the complexities of this study.In my biology class, we delved into the fascinating world of cells, the fundamental units of life. We learned about their structure, function, and the remarkable way they communicate and replicate. The vocabulary was challenging at first, with terms like "mitochondria," "cytoplasm," and "nucleus" becoming part of my daily lexicon. However, as I grew more comfortable with the terminology, I began to appreciate the precision and beauty of scientific language.One of the most engaging aspects of biology is its interdisciplinary nature. It intersects with fields such as chemistry, physics, and mathematics, which we explored through English-medium textbooks and lectures. This cross-disciplinary approach not only enriched my understanding of biology but also improved my ability to comprehend and communicate complex concepts in English.Experimentation is at the heart of biological research, and our classroom was often transformed into a laboratory. Weconducted experiments on photosynthesis, osmosis, and genetic inheritance, documenting our observations and results in detailed lab reports. Writing these reports in English was an exercise in clarity and precision, as we had to convey our findings in a manner that was both scientifically accurate and grammatically correct.The study of ecology and the environment also formed a significant part of our curriculum. We discussed the impact of human activities on ecosystems and the importance of conservation. Debates and group discussions in English sharpened our critical thinking and communication skills, as we had to present our viewpoints effectively and respond to counterarguments.Moreover, the exploration of human physiology and anatomy was a highlight for many students. We studied the human body's systems, from the circulatory to the nervous system, and how they work in harmony to sustain life. Describing these systems in English required a deep understanding of both the biological concepts and the language itself.In conclusion, biology is not just a scientific pursuit; itis a language-rich discipline that challenges us to think critically and communicate effectively. The English language, with its vast scientific vocabulary and expressive capabilities, serves as an excellent medium for exploring and understanding the complexities of life. Through biology, I have not only gained knowledge about the natural world but also honed my ability to express these wonders in the global language of English.。
徐州2024年07版小学三年级英语第3单元暑期作业考试时间：90分钟（总分:100）A卷考试人：_________题号一二三总分得分一、选择题(共计20题，共40分)1、What do you call a young squirrel?A. KitB. PupC. KittenD. Baby2、选择题：What is the largest land carnivore?A. LionB. TigerC. Polar BearD. Grizzly Bear3、What is the main ingredient in pancakes?A. FlourB. RiceC. CornD. Oats4、选择题：How many colors are in a rainbow?A. 5B. 6C. 7D. 85、How many legs does an octopus have?A. SixB. EightC. FourD. Ten6、What is the main ingredient in sushi?A. RiceB. NoodlesC. BreadD. Potato7、选择题：What is the main purpose of a clock?A. Measure weightB. Measure timeC. Measure temperatureD. Measure distance8、How many continents are there?A. FiveB. SixC. SevenD. Eight9、选择题：What is the name of the famous river that runs through London?A. ThamesB. SeineC. DanubeD. Nile10、What is the capital of Peru?A. LimaB. CuscoC. ArequipaD. Trujillo11、What do we use to measure length?A. ScaleB. RulerC. ThermometerD. Clock12、选择题：What instrument is used to measure time?A. RulerB. StopwatchC. ClockD. Thermometer13、What do we call a person who helps in emergencies?A. NurseB. FirefighterC. TeacherD. Chef14、What do we call the effect of the Earth's rotation on weather patterns?A. Coriolis EffectB. Trade WindsC. Jet StreamD. Ocean Currents15、选择题：What do we call the place where we go to learn about science?A. LaboratoryB. ClassroomC. MuseumD. School16、选择题：What is the color of a typical orange?A. GreenB. YellowC. OrangeD. Red17、选择题：What is the capital of South Korea?A. SeoulB. TokyoC. BeijingD. Bangkok18、What do we call the force that opposes motion?A. GravityB. FrictionC. TensionD. Compression19、Which vegetable is orange and long?A. PotatoB. CarrotC. CucumberD. Broccoli20、How many legs does a spider have?A. SixB. EightC. FourD. Two二、听力题(共计20题，共40分)1、听力题：A chemical reaction can release energy in the form of _____.2、听力题：Planets do not produce their own ______.3、听力题：A star will die after exhausting its ______.4、听力题：The chemical industry produces many ______ that we use daily.5、听力题：A ____ is a small, friendly animal often seen in gardens.6、听力题：The ______ has a sweet smell.7、听力题：The process of turning a liquid into a gas is called _______.8、听力题：The _______ provides food for many insects.9、听力题：Plants take in _______ through their leaves.10、听力题：We have a ________ (discussion) about topics.11、听力题：My mom makes _____ for dinner. (chicken)12、听力题：She is a great ________.We have music ______ every Friday. (class)14、听力题：The teacher asked us to _____ (read/write) the story.15、听力题：A chemical equation must be balanced to obey the law of ______.16、听力题：She likes to eat _____ (apples/television).17、听力题：The ______ is known for its beautiful song.18、听力题：A chemical change can be detected by changes in ______.19、听力题：The teacher is very ________.20、听力题：The chemical formula for vinegar is ______ acid.三、填空题(共计20题，共10分)1、填空题：We have ______ (课外活动) after school.2、填空题：I can create a world of imagination with my toy ________ (玩具名称).3、填空题：This ________ (玩具) is fun for the whole family.4、填空题：The _______ (犬) is often considered man's best friend.5、填空题：My dog gets excited when it's time for a _______ (散步).6、填空题：The _______ (Golden Age of Islam) was marked by advances in science and culture.I enjoy sharing my ______ (梦想) with my closest friends.8、填空题：I enjoy hiking to see beautiful ______ (风景) and wildlife.9、填空题：The __________ (历史的交汇) creates opportunities.10、填空题：The __________ (重要节日) commemorate significant events in history.11、填空题：The process of photosynthesis occurs in the ______ (叶子).12、小马) gallops across the field. 填空题：The ___13、填空题：My favorite season is _______ (秋天).14、填空题：I like to plant ________ in the spring.15、填空题：We have a ______ (有趣的) project about space.16、填空题：The sun shines brightly in the ______.17、填空题：A _______ (小鸽子) coos softly while resting.18、填空题：My dad encourages me to be __________ (有创造力的).19、填空题：The ________ (植物美学) enriches landscapes.20、填空题：We have a ______ (精彩的) program for students at school.。
九年级全一册重点英语单词九年级全一册的英语单词是学习英语必备的基础，掌握这些单词对于学生接下来的英语学习和考试都非常重要。
以下是九年级全一册重点英语单词的详细介绍。
Unit 1: School Life1. biology (n.) - the study of living organisms2. chemistry (n.) - the branch of science that deals with the composition, structure, and properties of substances3. geography (n.) - the study of the physical features of the earth and its atmosphere, and of human activity as it affects and is affected by these4. history (n.) - the study of past events, particularly in human affairs5. literature (n.) - written works, especially those considered of superior or lasting artistic merit6. physics (n.) - the branch of science concerned with the nature and properties of matter and energyUnit 2: Personal Information1. birthday (n.) - the anniversary of the day on which a person was born2. hobby (n.) - an activity done regularly in one's leisure time for pleasure3. nationality (n.) - the status of belonging to a particular nation4. occupation (n.) - a job or profession5. passport (n.) - an official document issued by a government, certifying the holder's identity and citizenship and entitling them to travel under its protection to and from foreign countries6. phone number (n.) - a sequence of digits allocated to each telephone line for identification and routing of callsUnit 3: Health and Fitness1. exercise (n.) - activity requiring physical effort, carried out especially to sustain or improve health and fitness2. healthy (adj.) - in a good physical or mental condition; in good health3. nutrition (n.) - the process of providing or obtaining the food necessary for health and growth4. sports (n.) - activities involving physical exertion and skill in which an individual or team competes against another or others for entertainment5. stress (n.) - a state of mental or emotional strain or tension resulting from adverse or demanding circumstances6. vegetarian (n.) - a person who does not eat meat but may eat animal products such as eggs or dairyUnit 4: Holidays1. celebrate (v.) - acknowledge (a significant or happy day or event) with a social gathering or enjoyable activity2. festival (n.) - a day or period of celebration, typically for religious reasons3. present (n.) - a thing given to someone as a gift4. tradition (n.) - the transmission of customs or beliefs from generation to generation, or the fact of being passed on in this way5. vacation (n.) - an extended period of leisure and recreation, especiallyone spent away from home or traveling6. wish (v.) - feel or express a strong desire or hope for something that is not easily attainableUnit 5: Science and Technology1. experiment (n.) - a scientific procedure undertaken to make a discovery,test a hypothesis, or demonstrate a known fact2. invention (n.) - the action of inventing something, typically a process or device3. laboratory (n.) - a room or building equipped for scientific experiments, research, or teaching, or for the manufacture of drugs or chemicals4. microscope (n.) - an optical instrument used for viewing very small objects, typically magnified several hundred times5. technology (n.) - the application of scientific knowledge for practical purposes, especially in industry6. theory (n.) - a supposition or a system of ideas intended to explain something, especially one based on general principles independent of the thing to be explainedUnit 6: Communication1. advice (n.) - guidance or recommendations concerning prudent future action, typically given by someone regarded as knowledgeable or authoritative2. conversation (n.) - a talk, especially an informal one, between two or more people in which news and ideas are exchanged3. language (n.) - the method of human communication, either spoken or written, consisting of the use of words in a structured and conventional way4. message (n.) - a verbal, written, or recorded communication sent to or left for a recipient who cannot be contacted directly5. speak (v.) - say something in order to convey information, an opinion, or a feeling6. write (v.) - mark (letters, words, or other symbols) on a surface,typically paper, with a pen, pencil, or similar implementUnit 7: Culture and Traditions1. art (n.) - the expression or application of human creative skill and imagination, typically in a visual form such as painting or sculpture, producing works that are appreciated primarily for their beauty or emotional power2. culture (n.) - the customs, arts, social institutions, and achievements ofa particular nation, people, or other social group3. dance (n.) - a series of movements that match the speed and rhythm of a piece of music4. tradition (n.) - the transmission of customs or beliefs from generation to generation, or the fact of being passed on in this way5. music (n.) - vocal or instrumental sounds (or both) combined in such a way as to produce beauty of form, harmony, and expression of emotion6. theater (n.) - a building or outdoor area in which plays, movies, or other dramatic performances are givenUnit 8: World Issues1. climate (n.) - the weather conditions prevailing in an area in general or over a long period of time2. disaster (n.) - a sudden event, such as an accident or a natural catastrophe, that causes great damage or loss of life3. environment (n.) - the surroundings or conditions in which a person, animal, or plant lives or operates4. pollution (n.) - the presence in or introduction into the environment of a substance or thing that has harmful or poisonous effects5. recycle (v.) - convert (waste) into reusable material6. waste (n.) - material that is not wanted; the unusable remains or by-products of somethingUnit 9: Travel and Transportation1. airplane (n.) - a powered flying vehicle with fixed wings and a weight greater than that of the air it displaces.2. boat (n.) - a small vessel for travel on water.3. train (n.) - a vehicle or conveyance that runs on rails and is propelled by steam, electricity, or an internal combustion engine.4. car (n.) - a wheeled motor vehicle used for transportation.5. bus (n.) - a large motor vehicle, typically having a long body, equipped with seats or benches for passengers, usually operating as part of a scheduled service on a route calling at a number of stops.6. bicycle (n.) - a vehicle with two wheels and a frame, propelled by pedals.Unit 10: Food and Nutrition1. fruit (n.) - the sweet and fleshy product of a tree or other plant that contains seed and can be eaten as food.2. vegetable (n.) - a plant or part of a plant used as food, typically as a savory dish or accompaniment.3. protein (n.) - any of a class of nitrogenous organic compounds that have large molecules composed of one or more long chains of amino acids and are an essential part of all living organisms, especially as structural components of body tissues such as muscle, hair, collagen, enzymes, and antibodies.4. carbohydrate (n.) - a substance, such as sugar or starch, that consists of carbon, hydrogen, and oxygen atoms, is an important energy source in the diet of animals, and is an important structural component of plants.5. fat (n.) - a ester of fatty acid and an alcohol, which is the chief constituent of the bodies of animals and plants.6. vitamin (n.) - any of a group of organic compounds that are essential for normal growth and nutrition and are required in small amounts in the diet because they cannot be synthesized by the body.Unit 11: Environment and Nature1. forest (n.) - a large area filled with trees and plants.2. ocean (n.) - a very large expanse of sea, in particular each of the main areas into which the sea is divided geographically.3. mountain (n.) - a large mass of earth and rock, rising above the common level or a large steep hill.4. river (n.) - a large natural stream of water flowing in a channel to the sea, a lake, or another river.5. animal (n.) - a living organism that feeds on organic matter, typically having specialized sense organs and nervous system and able to respond rapidly to stimuli.6. plant (n.) - a living organism of the kind exemplified by trees, shrubs, herbs, grasses, ferns, and mosses, typically growing in a permanent site, absorbing water and inorganic substances through its roots, and synthesizing nutrients in its leaves or stems by photosynthesis using the green pigment chlorophyll.Unit 12: Safety and Protection1. police (n.) - the civil force of a state, responsible for the maintenance of law and order, the prevention and detection of crime, and the enforcement of the criminal law.2. fireman (n.) - a person whose job is to extinguish fires and save people from burning buildings or other dangerous situations.3. doctor (n.) - a qualified medical practitioner.4. nurse (n.) - a person trained to care for the sick or infirm, especially ina hospital.5. ambulance (n.) - a vehicle equipped for taking sick or injured people to and from hospital quickly.6. helmet (n.) - a protective hat, typically made of hard material and worn by cyclists, motorcyclists, skiers, and others engaging in potentially hazardous activities.。
生物专业英语教学案生物化学与代谢途径生物专业英语教学案生物化学与代谢途径I. Introduction:In the field of biology, the study of biochemistry and metabolic pathways is crucial. This lesson aims to provide students with a comprehensive understanding of the fundamental concepts and processes involved in biochemistry and metabolic pathways.II. Objectives:1. To introduce the basic principles and concepts of biochemistry.2. To familiarize students with the major metabolic pathways.3. To develop students' ability to apply biochemistry knowledge in practical scenarios.III. Lesson Plan:A. Warm-up Activity:To engage students and assess their prior knowledge, begin the lesson with a brief interactive activity. Show images related to biochemistry and metabolic pathways, such as proteins, enzymes, and chemical reactions. Ask students to identify and explain what they know about these images.B. Introduction to Biochemistry:1. Define biochemistry and its significance in the field of biology.2. Explain the fundamental components of biochemistry: biomolecules, enzymes, and metabolic pathways.3. Describe the structure and function of biomolecules, including carbohydrates, lipids, proteins, and nucleic acids.4. Discuss the role of enzymes in biochemical reactions.C. Major Metabolic Pathways:1. Glycolysis:- Explain the process of glycolysis, including the conversion of glucose into pyruvate and the production of ATP.- Discuss the importance of glycolysis in energy production and its relationship to anaerobic respiration.2. Krebs Cycle (Citric Acid Cycle):- Introduce the Krebs Cycle as a central metabolic pathway.- Explain the step-by-step process of the Krebs Cycle, highlighting the production of ATP and electron carriers.3. Electron Transport Chain (ETC):- Discuss the role of the electron transport chain in oxidative phosphorylation.- Explain the generation of ATP through the transfer of electrons and the gradient-driven synthesis of ATP.4. Photosynthesis:- Provide an overview of photosynthesis as a metabolic pathway.- Describe the light-dependent and light-independent reactions and their integral role in energy conversion.5. Protein Synthesis:- Explain the process of protein synthesis, including transcription and translation.- Discuss the importance of DNA, RNA, and ribosomes in protein synthesis.D. Application and Practical Scenarios:1. Case Study Analysis:- Present real-life scenarios where knowledge of biochemistry and metabolic pathways is crucial.- Engage students in analyzing and solving the given cases using their understanding of the topics covered.2. Laboratory Experiment:- Conduct a simple laboratory experiment related to biochemistry and metabolic pathways.- Allow students to apply theoretical concepts practically, reinforcing their understanding.E. Conclusion:Summarize the key points discussed throughout the lesson, emphasizing the importance of biochemistry and metabolic pathways in biological processes. Encourage students to explore further in the field and utilize their knowledge in future research or professional careers.IV. Assessment:Assess students' understanding through various evaluation methods:1. Class participation and engagement during discussions.2. Individual or group assignments related to biochemistry and metabolic pathways.3. Case study analysis and problem-solving activities.4. Laboratory experiment performance and reporting.V. Resources:1. Textbooks and reference materials on biochemistry and metabolism.2. Visual aids, such as diagrams and models, to enhance understanding.3. Relevant online resources (without including specific URLs).Note: The format provided above is merely a suggestion. The actual formatting and sectioning of the lesson plan can vary based on personal preferences or institutional guidelines. As the instructor, feel free to modify and adapt the content as necessary to suit your teaching style and the needs of your students.。
2024年浙江省绍兴市高三英语第一学期期末统考试题考生请注意：1．答题前请将考场、试室号、座位号、考生号、姓名写在试卷密封线内，不得在试卷上作任何标记。
2．第一部分选择题每小题选出答案后，需将答案写在试卷指定的括号内，第二部分非选择题答案写在试卷题目指定的位置上。
3．考生必须保证答题卡的整洁。
考试结束后，请将本试卷和答题卡一并交回。
第一部分（共20小题，每小题1.5分，满分30分）1．Faced with economic slowdown, some companies are planning to use robots to ______ human workers to reduce their labor costs.A．compensate B．substituteC．symbolize D．discriminate2．That was not the first time he ____ us. I think it's high time we ____ strong actions against him.A．betrayed, take B．had betrayed, tookC．has betrayed, took D．has betrayed, take3．---Don’t worry, Mum. The doctor said it was only the flu.--- __________! I’ll tell dad there’s nothing serious.A．Congratulations B．What a reliefC．How surprising D．I’m so sorry4．---Mary was asked to do something important.---It doesn’t matter. Let’s the work where it is left off.A．take up B．take down C．take in D．take off5．The Oxford English Dictionary is necessary for learning English，so you'd better buy __________．A．this B．that C．it D．one6．Though Professor Liu ____ in New York for seven years, he has never regretted moving back to Shanghai, his hometown.A．lived B．has lived C．had lived D．was living7．----There won’t be anywhere to park.----Oh, _______. Let’s try the subway.A．that’s a r eal bargain B．that’s a good pointC．that’s really something D．that’s all settled8．We have strong ________ for believing that the newly-invented material is not only popular but also a monument to the eco-friendly lifestyle.A．grounds B．reasons C．causes D．purposes9．When she was in trouble, I did what I could to help her．__________ my help, she wrote me a letter of thanks．A．In honor of B．In case of C．In terms of D．In return for10．The debate here will be limited in two main respects，________ the time available. A．in view of B．in return forC．in addition to D．in comparison with11．By the time I saw the angry expression on his face, I ________ exactly what I was having to face.A．knew B．had known C．would know D．have known12．____ up early in the morning to have a walk, I am sure, you are likely to feel active all day．A．Get B．Having got C．Getting D．To get13．To be an expert, a beginner needs to go through a series of _____ stages. A．intermediate B．liberalC．overall D．demanding14．When he was running after his brother, the boy lost his ___ and had a bad fall. A．balance B．chanceC．memory D．place15．Most Schools have banned junk food and brought out new menus. “That’s cool!”said Andreas Petrou,11th grader.A．/; anB．/;theC．the; aD．the; /16．You should set a goal and see ________ you can achieve it in the coming exam. A．which B．whatC．whether D．when17．The teacher’s voice still remained calm ______ she was getting annoyed.A．as long as B．even ifC．as if D．now that18．Beijing’s new international airport into operation in 2019 will serve 72 million passengers annually.A．being put B．to be putC．put D．to put19．He works very hard in order to get himself ______ into a key university. A．accepted B．received C．announced D．admitted20．Some warned that the step the US government has taken to cope with the current crisis is ________ much risk.A．one of B．the one of C．the one D．that one第二部分阅读理解（满分40分）阅读下列短文，从每题所给的A、B、C、D四个选项中，选出最佳选项。
Exercise 4The Hill Reaction in Isolated ChloroplastsIntroductionPhotosynthesis is the process by which green plants, eucaryotic algae, cyanobacteria, and certain other prokaryotes convert light energy into chemical energy. In higher green plants and algae, the overall process can be summarized by the equation:light energy6CO2 + 12H2O -----------------> C6H12O6 + 6O2 + 6H2OchloroplastsWhile this equation is superficially correct, the actual process of photosynthesis is extremely complex and involves many separate reactions. The various reactions can be grouped into two sets, the light-dependent ("light") reactions and the light-independent ("dark") reactions. As the names suggest, the light-dependent reactions require the presence of a light source, while the light-independent reactions do not use light. It is in the light-dependent reactions that the energy of sunlight is trapped and converted to a form that can be used to drive other chemical reactions, such as the light-independent reactions of photosynthesis (Calvin Cycle) in which carbohydrates or other organic molecules are synthesized.The primary components of the light-dependent reactions are shown in Figure 1. For the purposes of this exercise, it is important to consider several aspects of these reactions. First, there are two distinct sets of light-dependent reactions, each with its own light-absorbing photosystem, photosystem I (PS I), and photosystem II (PS II). In each case, the energy in photons of visible light excites electrons in chlorophyll A, and this "excitation energy" is then transferred to other molecules. Second, the two primary products of the light-dependent reactions are ATP and NADPH2, energy-rich compounds that are required for the Calvin cycle; oxygen is also produced as a by-product. ATP is produced only as electrons pass through the electron transport chain of photosystem II, whereas the NADPH2 is formed when electrons pass through the entire pathway.Figure 1. Overview of the light-dependent reactions of photosynthesis.Light striking the photosynthetic pigments (principally chlorophyll A and B) excites electrons in these molecules, boosting the electrons to a higher energy state or orbital. The energy of excited electrons in these "antenna" pigment molecules in turn excites electrons in special molecules of chlorophyll A that comprise the photosystem "reaction centers". In PS II the reaction center chlorophyll A is called "P680", since this pigment absorbs light maximally at 680 nm. In PS I the reaction center chlorophyll A is called "P700", as it absorbs maximally at 700 nm.In PS II, excited electrons from P680 are transferred first to a molecule of quinone (Q) and then to an electron transport chain (ETC). As electrons are passed along the electron transport chain some of their energy is released and used to actively transport H+ into the thylakoids, thus providing chemiosmotic power for synthesizing ATP. The electrons lost from P680 are replaced by electrons liberated when water is split in thepresence of light, a process called photolysis. Note that photolysis of water also releases oxygen (O2) and protons (H+).In PS I, excited electrons from P700 are transferred first to ferridoxin. The electrons can either be passed back to the electron transport chain of PS II, thus creating a cyclic path for further ATP production, or they can be used in the reduction of NADP. In the latter case, 2NADP + 4e- + 4H+ combine to produce 2NADPH2. Note that the electrons lost by P700 are replaced by electrons from the electron transport chain of PS II. The H+ that combine with NADP are produced by the photolysis of water.The Hill ReactionIn 1937, Robert Hill discovered that isolated chloroplasts can generate oxygen when they are illuminated in the presence of a suitable electron acceptor, even if no carbon dioxide is present. This finding was a landmark in the study of photosynthesis because it was one of the first indications that the source of electrons in the light reactions is water, and it confirmed that the evolved oxygen comes from water rather than from carbon dioxide. Furthermore, it showed that a significant component of the light reactions can be studied in vitro using isolated chloroplasts. The Hill reaction is formally defined as the reduction of an electron acceptor (A) by electrons and protons from water, with the evolution of oxygen, when chloroplasts are exposed to light:lightH2O + A ----------------> AH2 + 1/2 O2chloroplastsThe final electron acceptor in vivo is NADP, while any of several artificial electrons acceptors can be used to study the Hill reaction in vitro.In this exercise you will study various factors that influence the light reactions of photosynthesis by monitoring the Hill reaction in chloroplasts isolated from spinach leaves (adapted from Bregman, 1990). As an artificial electron acceptor you will use the dye 2,6-dichlorophenol-indophenol (DCIP), which accepts electrons from the electron transport chain of PS II (and PS I). DCIP is blue in its oxidized form and colorless in its reduced form. As the Hill reaction proceeds, the reduction of DCIP can easily be measured as a change in absorbance at 600 nm. It is important to be awarethat, for various reasons, no ATP will be produced by your in vitro chloroplast preparation (Why not?).ReferencesBogorad, L. (1981) Chloroplasts. J. Cell Biology 91: 256s-270s. Bregman, A. (1990) Laboratory Investigations in Cell and Molecular Biology (3rd ed.). John Wiley and Sons, New York.Croft, A.R. (1967) Amine uncoupling of energy transfer in chloroplasts. I.Relation to ammonium ion uptake. J. Biol. Chem. 242: 3352-3359. Moreland, D.E. (1967) Mechanisms of action of herbicides. Ann. Rev.Plant Physiol. 18: 365-386.Refer to your textbook or other general references on cell biology, biochemistry, or plant physiology for information about the Hill reaction.ProceduresChloroplast IsolationThe following procedure will provide more than enough chloroplast suspension for 4 groups of students. One or two students should carry out the chloroplast isolation for the entire class. The procedures should be carried out in dim light to minimize photo-destruction of thechlorophyll.1. Weigh out 42 g of washed, fresh spinach (Spinacia oleracea) leaves fromwhich the major veins and petioles have been removed.2. Tear the leaves into small pieces and place in Waring blender with 160ml ice-cold Tris-sucrose buffer (0.3 M sucrose; 0.2 M Tris-HCl;: pH 7.5).5mMMgSO43. Blend at medium speed for 10 sec; check that all pieces of tissue are inthe liquid, and blend again for 10 sec.CAUTION: Don't over-homogenize!4. Filter the homogenate (called a brei by plant physiologists) through 8layers of cheesecloth into a cold flask.Divide the homogenate (or brei) equally among 4 chilled 40 ml centrifuge tubes and centrifuge for 5 min at approximately 1000 x g (2-4o C).7. Discard supernatant and gently resuspend chloroplast pellet in 12 ml ofcold Tris-sucrose buffer using a disposable pipette.8. This diluted chloroplast suspension will be used to measure the Hillreaction. Store in ice bath away from bright light until needed.Experiment I: Effects of Photosynthesis Inhibitors on theRate of the Hill ReactionIn the first experiment, you will examine the effects of two inhibitors on the rate of the Hill reaction. The first inhibitor is ammonia, which is commonly used as a source of nitrogen in fertilizers. However, when applied at a relatively high concentration (0.01 N) to isolated chloroplasts,ammonia (in the form of NH3) eliminates the H+ gradient across thethylakoid membrane, thereby acting as an uncoupler of electron transport and chemiosmotic synthesis of ATP (Crofts 1967). The second inhibitor is the herbicide 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU; known commercially as diuron), which inhibits the transport of electrons from photosystem II (Moreland 1967).As a control in this experiment, you will measure the rate of the Hill reaction in the absence of these inhibitors. Light intensity should be the same for all three reactions. To verify that the Hill reaction does indeed require light, you will also run a control in which the chloroplasts are kept in the dark.Since you will be working with light-sensitive reactions, you should take the following precautions to minimize "stray" light that could interfere with your measurements: Close all the blinds and turn off the room lights; do not leave tubes containing chloroplasts sitting in the light beam (except when running the Hill reaction); avoid shining your light onto another group's experiment.1. Prepare five cuvettes as shown in Table 1. You should add chloroplast suspension to the blank, but do not add the chloroplast suspension to tubes 1-4 until you are ready to start each assay .T ABLE 1. A SSAY MIXTURES FOR THE IN VITRO MEASUREMENT OF THE H ILL REACTION . C AUTION : D O NOT MOUTH PIPETTE ANY OF THE SOLUTIONS !Tube Tris-sucrose buffer DCIP (4 x 10-4 M) NH 4OH(0.01 N) DCMU (10-4M) Distilled water Chloroplast suspensionBlank 3.5 ml - - - 1.0 ml 0.5 ml1*3.5 ml 0.5 ml - - 0.5 ml 0.5 ml 2 3.5 ml 0.5 ml - - 0.5 ml 0.5 ml 3 3.5 ml 0.5 ml 0.5 ml - - 0.5 ml 4 3.5 ml 0.5 ml - 0.5 ml - 0.5 ml * Prepare a piece of aluminum foil to wrap around tube 1.2. Position the fluorescent light bulb horizontally, 5-10 cm above the bench top. Place a beaker of water 15-20 cm from the bulb to act as atemperature control bath. Do not move either the light or the water bath for the duration of the experiment. The precise temperature of the water is not critical, however the temperature should be the same for all threeassays. Monitor the water bath temperature closely, and use crushed ice or warm tap water to adjust the temperature during an assay.3. Set the spectrophotometer to 600 nm and use the blank tube to zero it, thereby compensating for the absorbance of the chloroplasts. You should periodically recheck the zero setting (before each absorbance reading, if possible).4. Thoroughly mix the chloroplast suspension before adding it to any assay tube. After adding the suspension to an assay tube, quickly cover the tube with Parafilm™ and invert it to mix the contents. Likewise, always mix each tube immediately before taking an absorbance reading . If any liquid runs down the outside of the tube, be sure to wipe it off before taking a reading.5. Add chloroplast suspension to tube #1, noting the time, mix, andimmediately read the absorbance. Quickly wrap the tube with foil. At the end of 10 minutes, mix, remove the foil, and read the absorbance. This tube should not be exposed to stray light!6. Add chloroplast suspension to tube #2, mix and immediately take anabsorbance reading (= 0 minutes). Quickly place the tube in the beaker of water in the light path and turn the light on.7. After one minute remove the tube, mix, dry the outer surface, and read theabsorbance. Replace the tube in the light path. Repeat at one minuteintervals for a total of 10 minutes.Note: If the absorbance reaches zero in less than three minutes, prepare a new tube #2 and repeat the assay with the beaker further from the light bulb (e.g., 30 cm).Note: Once the absorbance reaches zero, or if it stops changing before 10 minutes are up, you may stop the assay and proceed to the next step.8. Repeat steps 6 and 7 with tubes #3 and #4 (Do not change the temperatureor distance from the light.). At the end you should have absorbancereadings for the "dark control" at 0 and 10 minutes, and a series of 1minute readings from 0 to 10 minutes for tubes #2, 3, and 4. Experiment II: Other Factors Effecting the Hill ReactionFor this part of the exercise your group should devise a way to examine how other factors influence the rate of the Hill reaction. Forexample, you might consider changing temperature, intensity of light,buffer pH, or using other inhibitors. Your experiment should be designed to provide you with further insight into the light reactions and the process of photosynthesis in green plants. You should think about this before coming to lab, and your group should have an experiment already devised and approved by your instructorYou may use the same set-up as in the first experiment, including the same assay solutions and chloroplast suspension. If you need anyspecial solutions or equipment for your experiment you MUST make arrangements with your instructor the day before lab.ANALYSIS OF RESULTSIn both experiments you will need to determine the initial velocity of the reaction for each assay tube. The initial velocity is represented by the slope of a straight line drawn through the linear portion of a curve relating absorbance versus time, ignoring the negative sign.QUESTIONS TO CONSIDER1. What do the results from tubes #1 and #2 tell you about the eventsoccurring during the light reactions of photosynthesis? What is the role of the various chlorophyll-protein complexes in the light-dependentreactions?2. Why was no ATP synthesized by the isolated chloroplast preparation intube #2 (or any other tube, for that matter)? What assay conditions would be required to get ATP synthesis by isolated chloroplasts?3. Comparing the results from tubes #2 and #3, what can you concludeabout the effects of ammonia on the light-dependent reactions? Why is ammonia referred to as an "uncoupler;" that is, how does it affect thechloroplasts at the molecular level? Why is ammonia considered to be an "inhibitor" of photosynthesis?4. Comparing the results from tubes #2 and #4, what can you concludeabout the effects of DCMU on the light reactions? How does the action of DCMU on the light reactions differ from that of ammonia? Why is DCMU effective as an herbicide?5. Based on your results from the second experiment, what conclusions canyou draw about the light-dependent reactions of photosynthesis? How do your results relate to photosynthesis in green plants?5.What kinds of information can in vitro experiments on isolatedchloroplasts provide about the process of photosynthesis as it occurs in living green plants? What kinds of information about photosynthesis in green plants cannot be obtained from studies on isolated chloroplasts? Mar 2005 MA。
科学实验的英语作文As I stood in the laboratory, the smell of chemicals and the hum of equipment filled the air, I felt a surge of excitement. Today was the day we would conduct our first major experiment in the study of photosynthesis. The process was a fundamental part of biology, and understanding it could unlock thesecrets of life itself.The experiment was meticulously planned. We started bysetting up the equipment: a beaker filled with water and afew green leaves, a light source to simulate sunlight, and a collection of chemicals to test for the presence of oxygen. The objective was to demonstrate that green plants convertlight energy into chemical energy, releasing oxygen as a byproduct.We began by placing the leaves in the beaker and exposingthem to the light source. The room was quiet, save for the occasional whisper of excitement as we monitored the experiment. After a few hours, we carefully removed theleaves and tested the water for oxygen. The results were astonishing. The water had indeed become oxygen-rich, confirming the process of photosynthesis.This experiment was not just a lesson in biology; it was a testament to the power of scientific inquiry. It taught usthat the world is full of mysteries waiting to be uncovered, and that through careful observation and experimentation, wecan unlock their secrets.The process also highlighted the importance of patience and precision in scientific research. Each step had to be executed with care to ensure accurate results. It was a reminder that in the pursuit of knowledge, there are no shortcuts.As we cleaned up the lab and packed away our equipment, I couldn't help but feel a sense of awe. The simple act of placing leaves in water and shining a light on them had revealed a fundamental truth about the world we live in. It was a small experiment, but it had a profound impact on my understanding of science and its potential to change our lives.In conclusion, scientific experiments are more than just academic exercises; they are journeys into the unknown, where curiosity and diligence can lead to groundbreaking discoveries. As we continue to explore the world around us, may we always remember the lessons learned in the lab: to question, to observe, and to learn.。
Introduction:Photosynthesis is a fundamental process in which green plants convert light energy into chemical energy, producing oxygen and glucose in the process. This experiment aimed to investigate the effects of light intensity on the rate of photosynthesis in a specific plant species,such as spinach or lettuce. By manipulating the light conditions and measuring the resulting oxygen production or glucose accumulation, wecan better understand the relationship between light and photosynthesis.Objective:The objective of this experiment was to determine the effect of light intensity on the rate of photosynthesis in spinach leaves.Materials and Methods:Materials:- Fresh spinach leaves- Three light sources with varying intensities (e.g., 1000 lux, 2000 lux, and 3000 lux)- Three beakers- Sodium bicarbonate solution (NaHCO3)- Distilled water- Sodium hydroxide solution (NaOH)- pH test strips- Stopwatches- Light meters- Spectrophotometer- Chlorophyll extraction solution (e.g., 95% ethanol and 5% acetone)- Test tubes- Microscope- CameraMethods:1. Preparation of Plant Samples:- Harvest spinach leaves from a healthy plant and wash them thoroughly.- Remove any damaged or discolored leaves.- Cut the leaves into small, uniform pieces for consistent experimentation.2. Light Intensity Setup:- Place three beakers on a flat surface.- Position the light sources above the beakers, ensuring that the light is evenly distributed.- Use a light meter to measure the intensity of light at the level of the plant samples.3. Photosynthesis Experiment:- Place a small amount of spinach leaves in each beaker.- Add 10 mL of sodium bicarbonate solution to each beaker to provide a source of carbon dioxide.- Cover the beakers with lids to minimize evaporation and CO2 loss.- Record the initial pH of the solution using pH test strips.- Start the stopwatch and expose the spinach leaves to the light sources for 30 minutes.- After 30 minutes, turn off the light sources and remove the lids from the beakers.- Measure the pH of the solution again using pH test strips.4. Chlorophyll Extraction and Analysis:- Use a spectrophotometer to measure the absorbance of chlorophyll in the spinach leaves at a specific wavelength (e.g., 645 nm).- Prepare a chlorophyll extraction solution by mixing 95% ethanol and 5% acetone.- Transfer the spinach leaves into the extraction solution and incubate for 24 hours.- Measure the absorbance of the extracted chlorophyll solution at the same wavelength.- Calculate the chlorophyll content based on the absorbance values.5. Data Analysis:- Compare the pH changes in the solution of each beaker to determine the rate of photosynthesis.- Analyze the chlorophyll content in the spinach leaves to assess the overall health and photosynthetic activity.- Plot the data on a graph to visualize the relationship betweenlight intensity and photosynthesis rate.Results:The pH of the solution in each beaker was measured before and after the experiment. The results showed a decrease in pH in all beakers, indicating the release of carbon dioxide during photosynthesis. The rate of pH decrease was greater in the beakers with higher light intensities, suggesting that the rate of photosynthesis was higher under those conditions.The chlorophyll content in the spinach leaves was measured using a spectrophotometer. The results showed that the chlorophyll content was higher in the leaves exposed to higher light intensities, indicating increased photosynthetic activity.Discussion:The experiment confirmed that light intensity has a significant effect on the rate of photosynthesis in spinach leaves. As light intensity increases, the rate of photosynthesis also increases, as indicated by the higher pH decrease and chlorophyll content in the leaves exposed to higher light intensities.This finding aligns with the light reaction of photosynthesis, which occurs in the thylakoid membranes of chloroplasts and requires light energy to produce ATP and NADPH. Higher light intensity provides more energy for the light-dependent reactions, leading to increased ATP and NADPH production, which in turn enhances the light-independent reactions (Calvin cycle) and overall photosynthesis rate.Conclusion:This experiment demonstrated that light intensity plays a crucial rolein regulating the rate of photosynthesis in spinach leaves. By understanding the relationship between light and photosynthesis, we can optimize plant growth conditions and enhance crop yields. Further research could explore the specific mechanisms by which light intensity affects photosynthesis and its potential implications for agriculture and environmental science.References:- Demmig-Adams, B., & Adams, W. W. (2012). Plant biology. Pearson Education.- Arnon, D. I. (1949). Copper enzymes in isolated chloroplasts. Polyphenol oxidase in beta vulgaris. Plant Physiology, 24(1), 1-15.- light intensity and photosynthesis. (2020). In Photosynthesis (pp.265-284). Springer, Cham.。
“PEP”2024年小学六年级上册英语第三单元期末试卷考试时间:100分钟（总分:140）考试人：_________题号一二三总分得分一、(选择题)总分:20分(1分/题)1、Which word means to move quickly on foot?A) RunB) WalkC) JumpD) Sit2、What type of root system does a carrot have?中文解释：胡萝卜有什么类型的根系？A. TaprootB. FibrousC. Adventitious3、What do we call the time of day when it is dark?A) MorningB) AfternoonC) EveningD) Night4、What is the opposite of "hot"?A) WarmB) CoolC) ColdD) Freezing5、What do we call the protective covering of a seed?我们称种子的保护外壳为？A. Seed coatB. HuskC. ShellD. Pod6、What do we call a plant that grows in a pot inside a house?我们称在屋内盆栽的植物为？A. Indoor plantB. Outdoor plantC. Wild plantD. Garden plant7、What do we call the feeling of being happy?A) AngerB) SadnessC) JoyD) Fear8、Which month comes after June?A) MayB) JulyC) AugustD) September9、( )你想说“我是从中国来的。
”应该这么说:__________。
实验报告光合作用对植物生长的影响实验报告: 光合作用对植物生长的影响简介实验目的实验步骤实验结果实验分析实验结论简介光合作用是植物重要的生理过程之一，通过这个过程，植物能够将阳光能转化为化学能，并且释放出氧气。
本实验旨在探究光合作用对植物生长的影响，以此加深我们对光合作用的理解，同时也为植物生长的优化提供一定的参考依据。
实验目的1. 理解光合作用的基本原理和过程；2. 探究光照强度对植物生长的影响；3. 研究光合作用对植物生长速度及其它生理指标的影响；4. 提出关于光合作用对植物生长的合理建议。
1. 准备材料：种子、土壤、花盆、水壶、照明装置等；2. 分为三组实验：分别在不同光照条件下种植植物，设置为强光组、中光组和弱光组；3. 确保每组实验条件一致：土壤质量、湿度和温度等；4. 定期测量植物的生长情况：包括株高、叶片数量、根系生长情况、叶绿素含量等；5. 进行实验观察：每组实验进行至少4周，记录植物生长的变化；6. 结束实验：测量并记录实验结束时的各项指标。
实验结果经过四周的观察与记录，我们得到了以下实验结果：1. 强光组：在高光照的条件下，植物生长速度明显加快，株高增长明显，叶片数量增多，根系生长范围广。
叶绿素含量较高，表明光合作用活性强。
2. 中光组：在适中的光照强度下，植物生长比较均衡，株高增长适中，叶片数量适度增加，根系也有良好的发展。
叶绿素含量相对较高，光合作用活性较强。
3. 弱光组：在较低的光照条件下，植物生长速度较慢，株高增长缓慢，叶片数量较少，根系发育受限。
叶绿素含量较低，光合作用活性不高。
根据实验结果，我们可以得出以下结论：1. 光照强度对植物的生长速度和发育有明显影响。
适度的光照可以促进植物的光合作用，提高生长速度。
2. 光合作用对植物的生长非常重要。
光合作用不仅仅是为了植物能够正常生长，还通过释放氧气增加了大气中氧气的含量。
3. 根据实验结果，可以合理调整光照强度，优化植物生长环境，提高光合作用活性，并且促进植物生长。
Laboratory Exercise #5Photosynthesis and Cellular Respiration I. IntroductionAll organisms, except for a few types of chemosynthetic bacteria, are ultimately dependent upon photosynthesis for their source of food. Photosynthesis is a photo-biochemical process that converts light energy into chemical energy by utilizing water and carbon dioxide to produce sugar, usually glucose, while releasing oxygen gas as a by-product. Light energy is trapped by the plant pigment molecules known as chlorophylls, xanthophylls, and carotenes. The sugar molecules made by photosynthesis may be used by the plant cells for energy production in the process of cellular respiration or may be converted to starch, cellulose, fats, amino acids, and other molecules, which may be used in function, structure, or stored for later use. These molecules of the plant cell may serve as food for other organisms such as animals or microbes.Several types of organisms carry out photosynthesis and are thus self-feeding, or autotrophic. These include cyanobacteria, protistans, and plants. Perhaps the most noticeable photosynthetic organisms are the seed plants, many of which we are dependent on for food, shelter, clothing, and medicines. Most seed plants carry out photosynthesis in specially adapted organs known as leaves. Photosynthesis is a very complex multi-step process that can be represented by the following equation:Light6 CO2 + 12 H2O → C6H12O6 + 6 O2 + 6 H2OEnergy is the ability to do work. Energy comes in many forms: heat, light, electrical, mechanical, chemical, and nuclear. All living organisms use energy for movement, for heat production, for active transport, for growth, and for reproduction. In fact, one of the most basic activities of a cell is the transformation of energy from less useful forms to more useful forms. During photosynthesis, energy from sunlight is stored in sugars. During cellular respiration, sugar molecules are oxidized (broken down) and energy is released. All living things get their energy by cellular respiration. In your body, reactions that release energy occur within the cytoplasm and in the mitochondria of your cells. Cellular respiration can be represented by the following generalized equation:C6H12O6 + O2→ CO2 + H2O + ATP + HeatActivity #1: Leaf Transverse Sections1.Examine a prepared slide of transverse sections of a leaf with the 4X, 10X, and 40Xobjectives. Notice how the cells of each area are different in size, shape, andarrangement. The upper or dorsal leaf surface facing the sun will have a single layerof cells that have an external protective waxy coating, the cuticle, which protects theleaf from water loss. The upper epidermal cells do not contain chloroplasts.2.Immediately under the upper epidermis you will find an array of rectangular cellscalled the palisade mesophyll, which contains chloroplasts. The palisade mesophyllcells are tightly packed together along their axis so as to efficiently trap light. Thelower part of the leaf is composed of a loosed array of spongy mesophyll cellsamong which are air spaces for gas and water vapor movement. Spongy mesophyllcells contain chloroplasts. At intervals in the mesophyll region you will find leafveins, which are part of the plant’s vascular apparatus. Because the leaf veins run invarious directions, you may see cross, longitudinal, or tangential sections. Leaf veinsare composed of xylem and phloem cells. Xylem cells are usually stained red andare located on the upper side of the vein toward the palisade mesophyll layer. Xylemcells have an extra thick cell wall and are empty and dead at time of maturity. Thefunction of the xylem is to transport water and mineral ions to upward in the plantfrom the roots to the leaves. In addition, xylem provides structural support for theentire plant. Xylem helps keep the leaf blade expanded for absorption of sunlight,and large masses of xylem, called wood, keep the stem and branches upright. Belowthe xylem in the vein will be a number of smaller, thin walled cells, the phloem.These living cells transport products of photosynthesis in all directions throughout theplant. The lower or ventral side of the leaf has a single layer of epidermal cells calledthe lower epidermis. It also has stomata. Stomata consist of two guard cells,containing a few chloroplasts that surround a tiny opening, the stoma. The guardcells can open and close the stoma. When the stoma is open, carbon dioxide forphotosynthesis diffuses into the mesophyll while oxygen and water vapor diffuse out.3.Sketch the leaf cross section and label the structures in boldface.Photosynthesis: An organic endothermic reduction reactionWhen a leaf makes sugar the sugar is converted into starch almost immediately. The starch is stored right on the membranes of the chloroplasts in which its glucose subunits were made. Thus, a positive starch test indicates that sugar had been made by photosynthesis. We will use iodine as an indicator for the presence of starch and thus and indicator that photosynthesis did occur.Activity #2: Determining that light is necessary for photosynthesis.Geranium leaves were partially covered with a piece of cardstock with holes cut into it and then put in the dark overnight to “destarch”.1)What does this mean?______________________________________________________________________________ The plants were then put into high intensity light.2)What process will happen?________________________________________________________________________3)What products will be made?and(2) Take a leaf covered with cardstock. Before removing the cardstock, draw a picture of the leaf showing the placement of the hole.A.Remove cardstock.B.Boil leaf in water until limp, about 2 minutes. DO NOT over boil.C.Boil the same leaf in ethyl alcohol. BE CAREFUL! Alcohol boils at a muchlower temperature than water. Turn your hot plate down to simmer and do not letthe alcohol boil away. What color does the leaf turn?What color(s) does the alcohol turn?Chlorophyll is soluble in alcohol but not in water. Boiling the leaf in water breaksup the cells. Boiling the leaf in alcohol removes the chlorophyll from the leaf.That is why the alcohol turns green.D.Put the leaf into a Petri dish and put iodine on it. Remember that a positive starchtest is a dark color. (It might look more dark brown that blue-black.) Do you seea darker spot? Draw a picture of the leaf indicating the spot. Does the placementof the spot correspond to the original hole in the tin foil? You have proved thatis necessary for photosynthesis.Acitivty #3 (optional): Determining that chlorophyll is necessary for photosynthesisIf a plant needs light, it must have a way of absorbing it. Pigments are molecules that absorb some colors of light and reflect others. White light is made of all the colors of the spectrum. The pigment chlorophyll is green because it reflects green light and absorbs red and blue light. The chlorophyll molecules are on the grana membranes inside the chloroplasts, but chlorophyll isn’t the only pigment found in plants. Carotenes are yellow to orange.Xanthophylls are yellow. Anthocyanins are red, pink, blue, or purple. Carotenes and xanthophylls are also found in plastids. Anthocyanins are found in the plant cells’ large central vacuole.A. Pick a leaf from either a variegated Coleus or Geranium.A.Draw the leaf, labeling the exact placement of the different colors. Which parts of theleaf contain chlorophyll? Which do not contain chlorophyll? Can you see otherpigments? Where are they located?B.Boil the leaf in water until limp. Remove it and draw it, noting any color change.Did any of the colors leach out?C.Boil the leaf in ethyl alcohol. Draw it again, noting other color changes.D.Now, put the leaf into a Petri dish and put iodine on it. Any area that turns darkcontains starch. Draw the leaf, indicating the areas of positive starch.E.The areas of starch correspond to which original pigment areas?This experiment proves that is necessary for photosynthesis.Activity #5: Separation and Identification of Leaf PigmentsThe technique of chromatography is used widely to separate the individual components of a mixture of related substances – for example a mixture of amino acids, or one of sugars. The term “chromatography” refers to the fact that after separation, the individual substances may be visualized as spots of color, either because of their own natural color, or more commonly by causing them to react with reagents to yield a colored product. The first step in a chromatographic procedure is to apply a variety of substances to a supporting medium (i.e. chromatography paper). A suitable solvent is then used to move through the medium, and carries with it the mixture of components to be separated. Different components of the mixture travel at different speeds, depending on their affinity for the medium and their solubility in the solvent.One of the simplest chromatographic techniques is that of paper chromatography, in which the supporting medium is filter paper. In today’s laboratory you will separate plant pigments by paper chromatography. The predominant pigment in the leaves of green plants is chlorophyll, which occurs in two slightly different chemical forms called chlorophyll a and chlorophyll b. Most leaves contain at least two additional types of pigments, carotenes and xanthophylls, which are ordinarily not visible because they are masked by the more abundant chlorophyll.Paper Chromatography Procedure:A.Pigment Extraction. The leaf extract will be supplied to you. Or you maycollect leaf samples of your choice (directions given in the following section).B.Setting up the Chromatography “Chamber”. Study the apparatus shown in Figure5-1. You will use a large test tube as a chromatography chamber. The tube willbe sealed by means of a rubber stopper which has a wire hook attached. The filterpaper holding the pigment sample to be separated (directions given in thefollowing section) will be suspended from the hook so that the tip of the paperdips into the solvent, but none of the pigment is in the solvent.C.Add solvent (9 parts petroleum ether: 1 part acetone) to a depth of approximately½ cm to the chromatography chamber. Stopper the tube tightly, and place it anupright position in a clamp attached to a ring stand or in a flask. Allow the tubeto stand while you prepare the paper. During this time the air in the tube willbecome saturated with solvent vapor.Rubber StopperHookSolvent FrontSeparated PigmentsSolventFigure 5-1 Paper Chromatography Apparatus (courtesy, G.B. Reid)D.Preparation of Chromatography paper.1.Obtain a strip of Whatman #1 filter paper for use as your chromatogram.Handle the chromatography paper only by its edges, as oils andperspiration from your fingers can interfere with movement of thesubstances on the chromatogram.2. Place the strip on a clean sheet of ordinary paper and mark a line with apencil about 2cm from the tip. Do not use ink (Why not?)3.Place your leaf sample at the bottom of the strip and use a ruler to mark 2cm from the bottom.ing a coin with a serrated edge, press down firmly and roll along theruler edge several times to form a definite green line. Shift to a fresh areaof the leaf and repeat several times until the pencil line is coveredcompletely with a narrow green band. Allow to dry.5.Dispense 2mL of chromatography solvent in the large chromatographytest tube.6.Hold your chromatography paper next to the stoppered test tubecontaining the solvent. Try to determine the exact point at which the wireshould be inserted into the paper strip so that the tip of the strip will justreach the solvent. Make a small hole in the paper strip at this location.7.Remove the stopper from the test tube containing the solvent. Insert thehook through the upper end of the paper strip into the hole you made.8.Carefully lower the chromatography paper into the test tube until the tiptouches the solvent. Do not allow the solvent to touch the green line.(Thestrip should be positioned on the hook in such a way that when suspendedinside the tube, no part of the strip touches the side of paper.)9.When the pigments have separated into distinct bands, lift the paper out ofthe tube.E.“Developing” the Chromatogram. The solvent will move rapidly up the paperby capillary action. In its upward movement pass the pigment spot, the solventwill carry the pigments with it. However, because of their varying affinities forthe paper, as well as different solubilities in the solvent, the different pigmentswill be carried different distances, and will be seen on the paper as irregular“spots” or bands of colorRemove the paper strip from the tube when the solvent is approximately 2 cmbelow the hook from which the chromatogram is hanging. With a pencil, quicklymark the distance traveled by the solvent through the chromatography paperThis is called thesolvent front. Delay will allow the solvent to evaporate and thesolvent front will no longer be visible. As soon as the paper is dry, outline eachregion of pigment with pencil as faint spots fade.DO NOT POUR THE SOLVENT INTO THE SINK! Return it instead to the“Waste Solvent” container.F.Identification of Pigments.The distance the pigment molecules travel throughthe chromatograp hy paper, called the “relative front” or, is relative to the distancetraveled by the solvent front. In the solvent system which you used, the goldenpigment called carotenes move the fastest and appear near the top of the solventfront. In some leaves this pigment is followed in turn by a lighter band of paleryellow xanthophyll. Some chromatograms may contain bands of grayish leafbreak-down products in the region of the xanthophylls. These can be ignored. Aband of chlorophyll a lies below the xanthophyll layer. This band is followed bychlorophyll b. Some leaf specimens may contain a water-soluble pigmentcalled anthocyanin that shows at the base of the chromatogram. Besides theirlocation on the chromatogram, pigments can be identified by their characteristiccolors:PIGMENT CHARACTERISTIC COLORcarotenes orange to yellowxanthophylls pale yellow to grayishchlorophyll a bright green to grass-greenchlorophyll b olive-greenanthocyanins purplish-pinkThe ratio of the distance traveled by a particular substance to the distance traveled by the solvent, both measured from the original spot, constitutes the so-called ratio of fronts, or R f,for that substance. This R f value is constant for a given set of conditions, but changes when the conditions are changed, for example if a different solvent is used.1.Determine the R f values for each pigment on your chromatogram by measuring thedistance from the origin to (a) the solvent front and to (b) the center of each of thepigment spots. Compute the ratio in each case as follows:R f = distance from origin to center of pigmentdistance from origin to solvent front2.Express the R f value as a decimal (e.g., 0.75 or 0.24) without units.NOTE:For a precise identification of the pigments in an unknown mixture, a chromatogram of that unknown mixture is compared with chromatograms of known compounds run simultaneously using identical reagents and techniques.Activity #6: Yeast FermentationFermentation is a metabolic pathway that produces ethanol, carbon dioxide and two molecules of ATP in yeast during the anaerobic breakdown of one molecule of glucose. In thisexperiment you will be testing the ability of yeast to metabolize several carbohydrates and gelatin.You will work in pairs. Each table will test one solution. Your instructor will demonstrate how to do the set up. Data from all groups will be compared to determine which compounds yeast are able to break down anaerobically to produce energy (ATP).Equipment and supplies per table1. One fermentation tube2. Yeast3. One 25 or 50 ml graduated cylinder for measurement of solution into small tubesDO NOTPOUR SOLUTIONS BACK INTO STOCK BOTTLES IF YOU POUR TOO MUCH!!4. 5% solutions for testing.PROCEDURE1.Measure 20 mL of 5% test solution into the fermentation tube using a graduated cylinder.Set up the fermentation chambers as demonstrated, making sure there are no bubbles.ing a weigh boat, weigh 0.5g of yeast and place it into fermentation tubewith the testsolution (make sure all the yeast goes into the tube). Invert to mix.3.BEGIN TIMING IMMEDIATELY!!4.Allow to ferment for 45 minutes.5.After 45 minutes record how much water was displaced by gas produced duringfermentation. Report to the class whether or not yeast was able to break down yoursolution by fermentation to produce ATP energy.6.When finished rinse the fermentation tubes and graduated cylinders and leave at yourstation.DATA TABLE: Fermentation analysis of yeast at 400 C for 20 minutesREVIEW QUESTIONS1. On the basis of what you know about carbohydrates and anaerobic respiration, make predictions about which compound will ferment. Which do you think will react the fastest? WHY?2. Which of these compounds are monosaccharides? Which are disaccharides? Which are polysaccharides? Which are proteins?3. Several of the compounds will not react much, if at all. Explain why.。
