关于细胞的论文3000字高中英语
Outside the body of the medicine toxicity in the experiment， need to examine the chemistry medicine to the influence of cell propagate and survival， differ from the physiology phenomenon that the animal experiment can observe the animal directly， the experiment outside the body needs to examine the cell survival rate， but make use of the cell some life movable process to examine in the output material cell whether survival and the survival This experiment makes use of the MTA method to compare the color measurement， useding for the measurement H2O2 to the toxicity of the cell of H
你需要什么级别的答案？中国大学英语课，或者是外国中学生物课，还是外国大学生物课？
Cell (biology)The cell is the basic structural and functional unit of all known living It is the smallest unit of an organism that is classified as a living thing， and is often called the building block of [1] Some organisms， such as most bacteria， are unicellular (consist of a single cell) Other organisms， such as humans， are (Humans have an estimated 100 trillion or 1014 cells; a typical cell size is 10 µm; a typical cell mass is 1 ) The largest known cell is an unfertilized ostrich egg [2]In 1835 before the final cell theory was developed， Jan Evangelista Purkyně observed small "granules" while looking at the plant tissue through a The cell theory， first developed in 1839 by Matthias Jakob Schleiden and Theodor Schwann， states that all organisms are composed of one or more cells， that all cells come from preexisting cells， that vital functions of an organism occur within cells， and that all cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of [3]The word cell comes from the Latin cellula， meaning， a small The descriptive term for the smallest living biological structure was coined by Robert Hooke in a book he published in 1665 when he compared the cork cells he saw through his microscope to the small rooms monks lived [4][edit] General principles Mouse cells grown in a culture These cells grow in large clumps， but each individual cell is about 10 micrometres acrossEach cell is at least somewhat self-contained and self-maintaining: it can take in nutrients， convert these nutrients into energy， carry out specialized functions， and reproduce as Each cell stores its own set of instructions for carrying out each of these All cells have several different abilities:[5]Reproduction by cell division: (binary fission/mitosis or meiosis) Use of enzymes and other proteins coded for by DNA genes and made via messenger RNA intermediates and Metabolism， including taking in raw materials， building cell components， converting energy， molecules and releasing by- The functioning of a cell depends upon its ability to extract and use chemical energy stored in organic This energy is released and then used in metabolic Response to external and internal stimuli such as changes in temperature， pH or levels of Cell contents are contained within a cell surface membrane that is made from a lipid bilayer with proteins embedded in Some prokaryotic cells contain important internal membrane-bound compartments，[6] but eukaryotic cells have a specialized set of internal membrane [edit] Anatomy of cellsThere are two types of cells: eukaryotic and Prokaryotic cells are usually independent， while eukaryotic cells are often found in multicellular [edit] Prokaryotic cellsMain article: Prokaryote Diagram of a typical prokaryotic cellThe prokaryote cell is simpler than a eukaryote cell， lacking a nucleus and most of the other organelles of There are two kinds of prokaryotes: bacteria and archaea; these share a similar overall A prokaryotic cell has three architectural regions:on the outside， flagella and pili project from the cell's These are structures (not present in all prokaryotes) made of proteins that facilitate movement and communication between cells; enclosing the cell is the cell envelope – generally consisting of a cell wall covering a plasma membrane though some bacteria also have a further covering layer called a The envelope gives rigidity to the cell and separates the interior of the cell from its environment， serving as a protective Though most prokaryotes have a cell wall， there are exceptions such as Mycoplasma (bacteria) and Thermoplasma (archaea)) The cell wall consists of peptidoglycan in bacteria， and acts as an additional barrier against exterior It also prevents the cell from expanding and finally bursting (cytolysis) from osmotic pressure against a hypotonic Some eukaryote cells (plant cells and fungi cells) also have a cell wall; inside the cell is the cytoplasmic region that contains the cell genome (DNA) and ribosomes and various sorts of A prokaryotic chromosome is usually a circular molecule (an exception is that of the bacterium Borrelia burgdorferi， which causes Lyme disease) Though not forming a nucleus， the DNA is condensed in a Prokaryotes can carry extrachromosomal DNA elements called plasmids， which are usually Plasmids enable additional functions， such as antibiotic [edit] Eukaryotic cellsMain article: Eukaryote Diagram of a typical animal (eukaryotic) cell， showing subcellular Organelles:(1) nucleolus(2) nucleus(3) ribosome(4) vesicle(5) rough endoplasmic reticulum (ER)(6) Golgi apparatus(7) Cytoskeleton(8) smooth endoplasmic reticulum(9) mitochondria(10) vacuole(11) cytoplasm(12) lysosome(13) centrioles within centrosomeEukaryotic cells are about 15 times the size of a typical prokaryote and can be as much as 1000 times greater in The major difference between prokaryotes and eukaryotes is that eukaryotic cells contain membrane-bound compartments in which specific metabolic activities take Most important among these is the presence of a cell nucleus， a membrane-delineated compartment that houses the eukaryotic cell's DNA It is this nucleus that gives the eukaryote its name， which means "true " Other differences include:The plasma membrane resembles that of prokaryotes in function， with minor differences in the Cell walls may or may not be The eukaryotic DNA is organized in one or more linear molecules， called chromosomes， which are associated with histone All chromosomal DNA is stored in the cell nucleus， separated from the cytoplasm by a Some eukaryotic organelles such as mitochondria also contain some DNA Many eukaryotic cells are ciliated with primary Primary cilia play important roles in chemosensation， mechanosensation， and Cilia may thus be "viewed as sensory cellular antennae that coordinate a large number of cellular signaling pathways， sometimes coupling the signaling to ciliary motility or alternatively to cell division and "[7] Eukaryotes can move using motile cilia or The flagella are more complex than those of Table 1: Comparison of features of prokaryotic and eukaryotic cells Prokaryotes Eukaryotes Typical organisms bacteria， archaea protists， fungi， plants， animals Typical size ~ 1–10 µm ~ 10–100 µm (sperm cells， apart from the tail， are smaller) Type of nucleus nucleoid region; no real nucleus real nucleus with double membrane DNA circular (usually) linear molecules (chromosomes) with histone proteins RNA-/protein-synthesis coupled in cytoplasm RNA-synthesis inside the nucleusprotein synthesis in cytoplasm Ribosomes 50S+30S 60S+40S Cytoplasmatic structure very few structures highly structured by endomembranes and a cytoskeleton Cell movement flagella made of flagellin flagella and cilia containing microtubules; lamellipodia and filopodia containing actin Mitochondria none one to several thousand (though some lack mitochondria) Chloroplasts none in algae and plants Organization usually single cells single cells， colonies， higher multicellular organisms with specialized cells Cell division Binary fission (simple division) Mitosis (fission or budding)Meiosis Table 2: Comparison of structures between animal and plant cells Typical animal cell Typical plant cell Organelles Nucleus Nucleolus (within nucleus) Rough endoplasmic reticulum (ER) Smooth ER Ribosomes Cytoskeleton Golgi apparatus Cytoplasm Mitochondria Vesicles Lysosomes Centrosome Centrioles Vacuoles Nucleus Nucleolus (within nucleus) Rough ER Smooth ER Ribosomes Cytoskeleton Golgi apparatus (dictiosomes) Cytoplasm Mitochondria [edit] Subcellular components The cells of eukaryotes (left) and prokaryotes (right)All cells， whether prokaryotic or eukaryotic， have a membrane that envelops the cell， separates its interior from its environment， regulates what moves in and out (selectively permeable)， and maintains the electric potential of the Inside the membrane， a salty cytoplasm takes up most of the cell All cells possess DNA， the hereditary material of genes， and RNA， containing the information necessary to build various proteins such as enzymes， the cell's primary There are also other kinds of biomolecules in This article will list these primary components of the cell， then briefly describe their [edit] Cell membrane: A cell's defining boundaryMain article: Cell membraneThe cytoplasm of a cell is surrounded by a cell membrane or plasma The plasma membrane in plants and prokaryotes is usually covered by a cell This membrane serves to separate and protect a cell from its surrounding environment and is made mostly from a double layer of lipids (hydrophobic fat-like molecules) and hydrophilic phosphorus Hence， the layer is called a phospholipid It may also be called a fluid mosaic Embedded within this membrane is a variety of protein molecules that act as channels and pumps that move different molecules into and out of the The membrane is said to be 'semi-permeable'， in that it can either let a substance (molecule or ion) pass through freely， pass through to a limited extent or not pass through at Cell surface membranes also contain receptor proteins that allow cells to detect external signaling molecules such as [edit] Cytoskeleton: A cell's scaffoldMain article: Cytoskeleton Bovine Pulmonary Artery Endothelial cell: nuclei stained blue， mitochondria stained red， and F-actin， an important component in microfilaments， stained Cell imaged on a fluorescent The cytoskeleton acts to organize and maintain the cell's shape; anchors organelles in place; helps during endocytosis， the uptake of external materials by a cell， and cytokinesis， the separation of daughter cells after cell division; and moves parts of the cell in processes of growth and The eukaryotic cytoskeleton is composed of microfilaments， intermediate filaments and There is a great number of proteins associated with them， each controlling a cell's structure by directing， bundling， and aligning The prokaryotic cytoskeleton is less well-studied but is involved in the maintenance of cell shape， polarity and [8][edit] Genetic materialTwo different kinds of genetic material exist: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) Most organisms use DNA for their long-term information storage， but some viruses (， retroviruses) have RNA as their genetic The biological information contained in an organism is encoded in its DNA or RNA RNA is also used for information transport (， mRNA) and enzymatic functions (， ribosomal RNA) in organisms that use DNA for the genetic code Transfer RNA (tRNA) molecules are used to add specific amino acids during the process of protein Prokaryotic genetic material is organized in a simple circular DNA molecule (the bacterial chromosome) in the nucleoid region of the Eukaryotic genetic material is divided into different， linear molecules called chromosomes inside a discrete nucleus， usually with additional genetic material in some organelles like mitochondria and chloroplasts (see endosymbiotic theory)A human cell has genetic material in the nucleus (the nuclear genome) and in the mitochondria (the mitochondrial genome) In humans the nuclear genome is divided into 23 pairs of linear DNA molecules called The mitochondrial genome is a circular DNA molecule distinct from the nuclear DNA Although the mitochondrial DNA is very small compared to nuclear chromosomes， it codes for 13 proteins involved in mitochondrial energy production as well as specific tRNAForeign genetic material (most commonly DNA) can also be artificially introduced into the cell by a process called This can be transient， if the DNA is not inserted into the cell's genome， or stable， if it Certain viruses also insert their genetic material into the [edit] OrganellesMain article: OrganelleThe human body contains many different organs， such as the heart， lung， and kidney， with each organ performing a different Cells also have a set of "little organs，" called organelles， that are adapted and/or specialized for carrying out one or more vital There are several types of organelles within an animal Some (such as the nucleus and golgi apparatus) are typically solitary， while others (such as mitochondria， peroxisomes and lysosomes) can be numerous (hundreds to thousands) The cytosol is the gelatinous fluid that fills the cell and surrounds the Mitochondria and Chloroplasts – the power generators Mitochondria are self-replicating organelles that occur in various numbers， shapes， and sizes in the cytoplasm of all eukaryotic Mitochondria play a critical role in generating energy in the eukaryotic Mitochondria generate the cell's energy by the process of oxidative phosphorylation， utilizing oxygen to release energy stored in cellular nutrients (typically pertaining to glucose) to generate ATP Mitochondria multiply by splitting in Organelles that are modified chloroplasts are broadly called plastids， and are involved in energy storage through the process of photosynthesis， which utilizes solar energy to generate carbohydrates and oxygen from carbon dioxide and [citation needed] Mitochondria and chloroplasts each contain their own genome， which is separate and distinct from the nuclear genome of a Both of these organelles contain this DNA in circular plasmids， much like prokaryotic cells， strongly supporting the evolutionary theory of endosymbiosis; since these organelles contain their own genomes and have other similarities to prokaryotes， they are thought to have developed through a symbiotic relationship after being engulfed by a primitive [citation needed] Ribosomes The ribosome is a large complex of RNA and protein They each consist of two subunits， and act as an assembly line where mRNA from the nucleus is used to synthesise proteins from amino Ribosomes can be found either floating freely or bound to a membrane (the rough endoplasmatic reticulum in eukaryotes， or the cell membrane in prokaryotes)[9] Cell nucleus – a cell's information center The cell nucleus is the most conspicuous organelle found in a eukaryotic It houses the cell's chromosomes， and is the place where almost all DNA replication and RNA synthesis (transcription) The nucleus is spherical in shape and separated from the cytoplasm by a double membrane called the nuclear The nuclear envelope isolates and protects a cell's DNA from various molecules that could accidentally damage its structure or interfere with its During processing， DNA is transcribed， or copied into a special RNA， called mRNA This mRNA is then transported out of the nucleus， where it is translated into a specific protein The nucleolus is a specialized region within the nucleus where ribosome subunits are In prokaryotes， DNA processing takes place in the Diagram of a cell nucleus Endoplasmic reticulum – eukaryotes only The endoplasmic reticulum (ER) is the transport network for molecules targeted for certain modifications and specific destinations， as compared to molecules that will float freely in the The ER has two forms: the rough ER， which has ribosomes on its surface and secretes proteins into the cytoplasm， and the smooth ER， which lacks Smooth ER plays a role in calcium sequestration and Golgi apparatus – eukaryotes only The primary function of the Golgi apparatus is to process and package the macromolecules such as proteins and lipids that are synthesized by the It is particularly important in the processing of proteins for The Golgi apparatus forms a part of the endomembrane system of eukaryotic Vesicles that enter the Golgi apparatus are processed in a cis to trans direction， meaning they coalesce on the cis side of the apparatus and after processing pinch off on the opposite (trans) side to form a new vesicle in the animal [citation needed] Diagram of an endomembrane system Lysosomes and Peroxisomes – eukaryotes only Lysosomes contain digestive enzymes (acid hydrolases) They digest excess or worn-out organelles， food particles， and engulfed viruses or Peroxisomes have enzymes that rid the cell of toxic The cell could not house these destructive enzymes if they were not contained in a membrane-bound These organelles are often called a "suicide bag" because of their ability to detonate and destroy the [citation needed] Centrosome – the cytoskeleton organiser The centrosome produces the microtubules of a cell – a key component of the It directs the transport through the ER and the Golgi Centrosomes are composed of two centrioles， which separate during cell division and help in the formation of the mitotic A single centrosome is present in the animal They are also found in some fungi and algae [citation needed] Vacuoles Vacuoles store food and Some vacuoles store extra They are often described as liquid filled space and are surrounded by a Some cells， most notably Amoeba， have contractile vacuoles， which are able to pump water out of the cell if there is too much [edit] Structures outside the cell wall[edit] CapsuleA gelatinous capsule is present in some bacteria outside the cell The capsule may be polysaccharide as in pneumococci， meningococci or polypeptide as bacillus anthracis or hyaluronic acid as in [citation needed] Capsules not marked by ordinary stain and can detected by special The capsule is The capsule has antiphagocytic function so it determines the virulence of many It also plays a role in attachment of the organism to mucous [citation needed]
Drug toxicity in the in vitro experiments， the need for the testing of chemical substances on cell survival and multiplication effect from animal experiments can directly observe animal physiological phenomenon， in vitro experiments testing cell survival needs， and the use of cell life activities， have a material is to detect cell survival and survival The experimental use MTA France colorimetric measurement for determining the toxicity of H2O2 for Hela
关于细胞的论文3000字高中
中国的学生当不当自力、自强？答案是肯定的——中国学生应当学会自立自强。然而在实际生活中，有些中国学生却是懒惰的，依赖感十分强，他们在儿时依赖父母，在学习上依赖老师，在社会上依赖朋友。 有个故事，说一个十来岁的孩子，一次与同学在外面吃饭，吃到鸡蛋时，他说这里的鸡蛋不好吃，和家里的不一样。问他怎么不一样，他说是太硬了，家里的鸡蛋是白皮的，很软，拿着就能吃。原来，他父母一直把鸡蛋剥了皮才给他吃。一个十几岁的孩子，竟连鸡蛋皮都不懂剥，这简直是个天大的笑话，然而事实却是如此，这孩子的自理能力实在太低了，难道我们不应学会自立自强，自己的事自己做吗？ 报纸上曾经有这样一则骇人听闻的消息：××名牌大学的一位优秀学生自杀了。究竟是什么原因让这位学习成绩优异的大学生自杀了呢？原来他是由于生活的困扰：不懂去买饭，不懂洗衣服，，不懂整理自己的房间……也许我们会觉得好笑，但放眼望去，又有多少孩子不懂自己洗衣服，不懂为自己做一顿饭，难道我们不应学会自立、自强，自己去做力所能及的事吗？有人活了十八岁，连吃一个桃子都不懂得自己洗，有人上了初中，生病连药都不懂自己买，更甚至有人读了三四年，书连书包都不懂整理，有人……他们只是一味的衣来伸手，饭来张口，他们就像高高在上的小皇帝，而他们的父母则是呼之则来，挥之则去的仆人，指东不敢往西，这些“小皇帝”真是够威风的了。我们常可以看到，外国的许多孩子的妈妈是一个“狠心”的妈妈，外国的许多孩子的爸爸是也“残忍”的爸爸。比尔盖茨，世界首富，然而他却将自己的财产捐献给自己的祖国，只留下那么很少的一点钱给自己的子女，并要求他们自己出去打工赚钱。外国妈妈看到儿子摔倒；毅然不去扶他，外国孩子向父母借钱，要写借条；外国孩子旅游，要去自己赚钱，而中国学生只要问父母就行了，这难道不是巨大的反差？愿天下的父母让自己的孩子学会自立、自强，愿天下的孩子们学会自立、自强。
一共两篇看看吧①生物科技小论文——草莓的无土栽培作者：孔凡阳 草莓的无土栽培摘 要：1、利用学校的生物园地，通过配制合理的营养液，完全 可以进行草莓的无土栽培。 2、无土栽培的草莓具有生长速度快、长势好、花芽分化 早、开花结果早、产量高的特点。 关键词：培养基、营养液、无土栽培、简单易行 将作物栽培在除土壤以外的培养基上，叫无土栽培。无土栽培具有不占地或少占地、换茬快、环境清洁、产品无污染和生长好、品质优、色鲜味美等优点，为花卉蔬菜、粮食以及水果生产的工业化、自动化开辟了广阔的前景。一、实践目的 通过对草莓的无土栽培实践活动，使我们初步掌握无土栽培的技术，懂得利用水培法来确定植物必须矿质元素的原理和矿质元素对植物的生理作用，同时也培养了同学们的学习兴趣和实践能力。二、实践原理 植物根从土壤溶液中吸收水分和无机盐，土壤颗粒主要起着固着作用。根据这一原理，将植物生活所需的无机盐按一定比例配成营养液进行作物的无土栽培。三、实践方法 采用与泥土盆栽草莓相对照试验，盆栽草莓使用一般的菜园土作固着物，施用化肥和农家肥，进行水肥管理。四、实践器材 无土花盆（双层塑料套盆或采用罐头瓶、硬泡沫塑料做定植板也行）、草莓苗、营养液原液、天平、洗净的碎石或蛭石、温度计等。五、 试验与管理 1、试验时间：1997年9月－1998年5月；1998年9月－1999年5月 2、试验地址：校生物园 3、营养液原液：经试验得知，表1为最佳配方。 4、栽培方法：选择无病虫害、植株矮壮、具4－5片叶、顶芽饱满的壮苗，洗净根上泥土后，定植在无土花盆的上盆中，用碎石子或蛭石作固着物，下盆中盛清水，待长出新根后（1周左右）将清水倒掉，换上培养液。 表1 无土栽培草莓营养液原液配方成分名称 含量（MG/L） 硝酸钙 236 硝酸钾 303 磷酸铵 57 硫酸镁 123 三氯化铁 500 硼 酸 2 氯化锰 725、管理： （1）及时添加营养液。每周补液1－2次。每次50－100ml。进入4月份以后，气温升高、蒸发快，同时正当开花、结果盛期，需肥量大，每2－3天补液1次，并要增加营养液的浓度。一般开花前培养液浓度是原液∶水＝1∶9开花后培养液浓度为原液∶水＝7∶3 （2）隔天上午喷水1次，4月开始每天喷水1次，保持相对湿度70－80％。 （3）光照为生物园里的自然光照（注意不要放在直射太阳光下，以免培养液温度升得过高造成根坏死）。 （4）注意及时摘除老叶、匍匐茎。当发现植株下部的叶片呈水平着生，开始发黄、叶柄基部也开始变色时，应立即摘除。匍匐茎消耗养分大，为保证果大质优，发现生在叶片基部的幼嫩线状物——匍匐茎，要及时摘除。 （5）注意病虫害防治。草莓虫害主要有蚜虫和红蜘蛛，可用内吸杀虫剂防治，如甲胺磷、乐果等。病害主要有灰霉病、病毒病等，可用波尔多液、托布津等杀菌剂防治。 （6）注意及时疏蕾垫果。六、观察记录情况 1、根系在2℃时开始活动，在7℃时开始长新根，最适生长温度为15－20℃，高于30℃时停止生长，并有根部变色受害情况，在－8℃时根系受到冻害。 2、地上茎、叶气温在5℃时开始生长，生长最适气温为15－25℃气温过高过低生长都较缓慢，气温高于30℃以上有老叶焦边现象。 3、气温在5℃以上开始花芽分化，花芽分化最适气温在5－15℃之间，开花在10℃以上，开花盛期在15℃左右。 4、培养液pH值在5-7最为适宜。 5、开花结果情况见下表表2 无土栽培草莓开花结果记录统计表盆数 盆栽时间 第一花序 第二花序 总果实／株 月／日 叶片数 开花月／日 小花朵数 果实成熟月／日 开花月／日 小花朵数 果实成熟月／日 数量 重（克） 20 9／239／26 4－5 3／234／6 11－17 4／124／27 4／104／21 5－9 4／205／18 9－171 53－257七、结果与体会 1、无土栽培的草莓比盆栽草莓生长速度快、长势好、花芽分化
1995年以来我国造血干细胞工程与相关的生物学领域的研究发展迅速。有关造血干/祖细胞基因表达的研究，上海国家人类基因组研究中心陈竺、陈赛娟等为正常和急性白血病人骨髓造血干祖细胞cDNA文库的基因表达建立了一套先进的工作体系。他们在许多白血病细胞系的干/祖细胞中发现了300个新的相关基因。中山大学医学院李树浓、黄绍良等从人的桑葚期胚胎干细胞成功地诱导出造血细胞等。北京输血研究所裴雪涛等从成人和胎儿的骨髓分离出成年源干细胞，又进一步诱导分化为骨、软骨、脂肪和神经原细胞等。他们成功地构建了胎儿和成人间充质干细胞cDNA扣除文库，获得了胎儿和成人间充质干细胞的差异表达基因及在胎儿特异表达基因。中国医学科学院天津血液学研究所、国家血液学重点实验室赵春华等证实从胚胎胰腺、骨髓和肝脏中都可以分离出人间充质干细胞，又证明G-CSF可以使输注的间充质干细胞在体内促造血重建。北京基础医学研究所毛宁等的实验不支持间充质干细胞可以“横向分化“。最近他们发现小鼠胚胎干细胞的体外分化重现了胚胎早期造血发生的生物学程序以及Smad5基因调控在胚胎造血发生中的必要性和多样性，又表明其上游配体TGF-beta家族分子在胚胎发生中的作用和特点。本文针对干细胞可塑性研究作了评论。国际上曾风靡一时的“横向分化“有关的实验都没有用完全纯化的胚层干细胞或组织干细胞来证实。然而，完全纯的胚层或组织定向的干细胞克隆是无法制备的。成年或胎儿全身各类组织中混有一些定向某胚层的或某组织的干细胞，甚至还混有桑葚胚干细胞。它们是胚胎发育过程的每个阶段中停止参与胚胎发育而残留下来的。它们在体内处于静止期，寿命长，长期存留在成人的各种组织中。各胚层和组织干细胞混杂在一起，它们都没有特异的形态、表型和功能，无法分离纯化，甚至和成人组织细胞也很难分开。它们在体外实验适当的条件诱导下可分化为各种组织细胞。在那些想证明组织干细胞“横向分化“的实验中，都无法排除上述可能。本专论指出，只有桑葚胚干细胞是全能的胚胎干细胞，具有向各个胚层分化的潜能，即具有全能分化的可塑 性。当它发育成为各个胚层的或各种组织的干细胞时，它的分化潜能只限于本胚层或本组织，不能向其它胚层其它组织分化。本专论又指出间充质干细胞的制备过程很长，经过许多次的换代。等到出现许多分化抗原标志时，已经是后代的各种不同的成熟间充质细胞了。当然，它们的存在可证实最初培养的是间充质干细胞。大量扩增后所获得的集落主要是各种成熟的间充质细胞，其中也包含一些未来参与分化的间充质干细胞和中胚层干细胞。间充质干细胞和造血干细胞都是来自中胚层。然而它们都是培养中的贴壁幼儿，无法区分也无法分离它们。因此在实验中无法排除所制备的间充质干细胞样品中，绝对没有中胚层或其它胚层干细胞的存在。至今，完全纯化的间充质干细胞是不可能制备的。所以，很可能从间充质干细胞体外诱导出各类不同的，甚至内、外胚层的组织细胞，切不可轻率地推率为“横向分化“。临床支持造血干/祖细胞移植的，主要是成熟而有调控功能的各种间充质细胞。总之，“横向分化“等的推论缺乏实验证据，在生物自然界和人类疾病史中都找不到佐证。想要推翻经无数科学家实践充分证明了的细胞遗传学的最基本原理，必须在生物自然界找到非常充足的科学证据唐佩弦 军事医学科学院基础医学研究所 我国造血干细胞基础研究的新进展兼论干细胞可塑性
这是锻炼自己的时候。 最好靠自己、
关于细胞的论文3000字高中版
人体细胞是人体的结构和功能的基本单位。共约有40万亿-60万亿个，细胞的平均直径在10-20微米之间。除成熟的红血球和血小板外，所有细胞都有至少一个细胞核，是调节细胞生命活动、控制分裂、分化的遗传控制中心。人体细胞中最大的是成熟的卵细胞，直径在200微米左右;最小的是血小板，直径只有约2微米。肠粘膜细胞的寿命为3天，肝细胞寿命为500天，而脑与骨髓里的神经细胞的寿命有几十年，同人体寿命几乎相等。血液中的白细胞有的只能活几小时。在整个人体中，每分钟有1亿个细胞死亡。
关于细胞的论文3000字高中生
你是学医的？还是什么问题？
“细胞增殖是生物体生长、发育、繁殖和遗传的基础”的命题，只要求解释细胞增殖与生物体生长的因果关系。细胞周期是本单元知识的核心概念之一，教学时，首先让学生依据上面的图示表述细胞周期的定义，进而通过识图和分析，说出一个细胞周期的起止时间和划分的阶段。然后，教师用板书形式概括细胞周期划分的阶段及细胞分裂的方式。间期是细胞分裂期的准备阶段。教学时，首先提示学生依据细胞周期的图解说出间期的起止时间和持续时间的长短；进而在阅读课文的基础上，用表格整理间期细胞的代谢状况。最后，让学生概述间期细胞的主要特征，以及在细胞周期中的地位。有丝分裂是真核细胞的主要分裂方式，其知识点应包括：植物细胞有丝分裂、动物细胞有丝分裂、细胞有丝分裂的特征、细胞有丝分裂的意义。标准要求“观察细胞的有丝分裂并概述其过程”，按照这个要求，植物细胞有丝分裂的教学应先组织学生观察植物根尖细胞有丝分裂的制片，对照图片从显微镜视野中识别间期细胞和有丝分裂的各个时期细胞。在学生对植物细胞有丝分裂过程具有初步感性认识的基础上，教师再借助挂图、图片或录像等教学媒体，依次阐述有丝分裂各个时期细胞的分裂相，然后师生共同以表格的形式归纳植物细胞有丝分裂过程中发生的核、质分裂相变化。最后，组织学生独立完成制作和观察根尖临时压片，在亲自制作的根尖临时压片中寻找和鉴别各个分期细胞的核、质分裂相。为了帮助学生理解有丝分裂中DNA和染色体的动态变化，也可以组织学生用不同颜色的塑料或橡皮泥塑成染色体，模拟染色体行为和数量的动态变化。在细胞有丝分裂的教学过程中，组织学生制作并观察植物细胞有丝分裂装片是十分必要的，这个实验活动有助于提高学生的制作装片、显微观察和绘制生物图等基本技能。教学时，首先阐述制作洋葱根尖细胞有丝分裂临时装片的程序，进而演示制作装片的方法。然后指导学生制片和观察，并根据观察画出细胞有丝分裂各个时期的简图。在组织学生制作并观察植物细胞有丝分裂装片时，安排一定时间让他们观察马蛔虫卵细胞分裂的制片，识别细胞两极的中心体结构和核、质分裂状况，从而为比较动物细胞有丝分裂与植物细胞的异同，归纳细胞有丝分裂的特征打下基础。细胞有丝分裂是一个连续的过程，为了研究和揭示有丝分裂的具体过程中染色体和DNA分子的变化规律，人为地将其分为不同的时期。因此，教学中不仅要阐明分裂间期为分裂期进行着物质和能量的准备，而且还要揭示细胞分裂过程中染色体与纺锤体的动态变化及两者之间的关系，以此培养学生事物是相互联系，不断运动和发展的观点。细胞有丝分裂过程的特征可概括为：染色体复制一次后，平均地分配到两个子细胞中去，从而将亲代遗传信息传递给子代。为了强调细胞有丝分裂的重要意义，可用下面的曲线图概括细胞有丝分裂过程中DNA数量和染色体动态和数量之间的变化关系及规律。细胞无丝分裂最主要的特征是没有出现染色体和纺锤丝的变化。教学时，结合洋葱表皮细胞或蛙蟾类红细胞无丝分裂的图解描述无丝分裂过程，首先强调细胞分裂过程也分为核分裂和质分裂，然后启发学生比较无丝分裂的核质分裂相与有丝分裂的异同，从而理解细胞无丝分裂的主要特征。2 细胞分化、衰老和凋亡的教学前面提到，细胞增殖、分化、衰老和凋亡是细胞的正常生命活动，这些生命活动是细胞的行为表现，而不能误认为是细胞发育的4个阶段。这是因为细胞凋亡不是衰老细胞的死亡，细胞凋亡与细胞增殖都是维持生物体内细胞动态平衡的基本行为。因此，本单元教学的开始，可以蛙的个体发育为实例，概述细胞增殖、分化、衰老和凋亡之间的复杂关系，如下：本单元知识包含一系列概念，是教会学生学习概念的良好素材。高中生物的概念学习方法主要是：分析典型的正确例证，揭示一类事物的共同本质特征，进而以下定义的形式加以表述并赋予名称，最后确认概念应用的范围。因此，在细胞分化的教学中，首先借助图片、录像等媒体展示未分化的干细胞、分化的肌肉细胞、神经细胞、红细胞和胰岛分泌细胞（也可以植物细胞为例），引导学生认识到分化细胞与未分化细胞在形态、结构和功能上发生的差异，从而理解细胞分化的概念，进而列举受精卵与人体组织的发生、植物茎的形成层与木质部和韧皮部的形成等实例，使学生明确细胞分裂不仅发生在胚胎发育阶段，而且贯穿于生命个体的终生，以补充衰老和死亡的细胞。然后，以红细胞和胰岛细胞为例，阐明红细胞具有其他细胞没有的血红蛋白，胰岛细胞可分泌胰岛素，这表明分化细胞具有某种特殊的功能，这种特殊功能可以通过蛋白质表现出来，而蛋白质是基因表达的产物。由此，引导学生推理得出“细胞分化是基因在特定条件下选择性表达的结果”这一结论。细胞全能性的原意指受精卵的分化潜能。上课前一周，要布置学生搜集有关干细胞研究进展和应用的资料。教学时，先以植物组织培养或以动物克隆为实例，说明分化的细胞仍然保持其全能性；进而用动物细胞的核移植技术进一步说明细胞核的全能性。这些实例使学生认识到分化细胞的细胞核中含有本物种的全部核基因，因此，分化细胞与受精卵一样，具有分化出各种细胞和组织，形成一个完整个体的潜能。这样，细胞全能性的定义应运而生。在此基础上，可结合图解介绍造血干细胞的培养和分化，组织学生交流有关干细胞研究进展和应用的资料，讨论研究干细胞与人类健康的关系。细胞衰老又叫细胞老化，是指在正常情况下，随着年龄增长内稳态下降，机体组织细胞发生退行性变化并趋向死亡的不可逆现象。由于细胞衰老与个体衰老具有同步性，所以，教学时先启发学生从宏观上描述呈现衰老体态的老年人的面部特征，如老年斑、皮肤干燥和皱纹等；然后，让学生阅读课文，从微观角度初步认识衰老细胞的结构和功能的特征（如下表）：细胞凋亡是细胞发育过程中由基因引发的自动结束生命的生理过程。教学时，通过列举人体神经系统形成过程中的细胞凋亡的现象，以及健康成人的骨髓和肠黏膜上皮细胞凋亡的现象，使学生明确在胚胎发育阶段通过细胞凋亡清除多余或完成使命的分化细胞，保证胚胎发育正常；在成体发育阶段通过细胞凋亡清除衰老和病变的组织细胞，保证机体健康。因此，不能将细胞凋亡与细胞衰老而死亡混为一谈。最后，组织学生讨论如何延缓细胞衰老，关注老年人的健康问题。3 细胞癌变的教学细胞癌变的教学可以放在细胞分化部分，也可以与细胞的衰老和凋亡放在一起。学生对细胞癌变知之甚少，上课前布置他们搜集恶性肿瘤及防治方面的资料。教学可采用讨论式，让学生围绕以下问题展开讨论：什么是癌？癌细胞的主要特征是什么？细胞发生癌变的根源是什么？诱发原癌基因发生突变的因素是什么？怎样防治恶性肿瘤等等。针对上述问题开展的讨论活动，不仅有利于激发学生的兴趣和调动他们的学习主动性，而且还可以考查学生的学习能力、处理信息的能力、分析和解决问题的能力，以及他们的情感态度与价值观。 上述对“细胞的增殖、分化、衰老和凋亡”的教学构思是粗糙和肤浅的，但愿能够起到抛砖引玉的作用，深入学习和领会高中生物课程标准的精神，推动高中生物教学改革和提高生物教学质量。
细胞生产生物制品论文同学，有，。。
关于细胞的论文800字高中
一天晚上，小昊体内的脑细胞、白细胞、红细胞、上皮细胞、肝细胞、神经细胞都想当国王，他们为了国王的位置争吵起来，甚至大动干戈，一场“世纪之战”打响了。第一个出场的是骄傲的肝细胞，只见他昂起头、眼睛里流露出轻蔑的眼神，“哼”了一声说：“我能净化人体内的许多东西，只有我才能当上国王。”而高大威猛、气势强盛的白细胞马上站出来，粗声粗气地反驳他：“我能为人体抵抗细菌，倘若没有我，人类就会失去免疫力，很容易生病，我才可以当真正国王，你们都不配。”站在一边的运输兵红细胞听了，气势汹汹地说：“我能为人类运输氧气和血液，没有我人类就不能生存，我才是当国王的不二人选。”这时，一辆闪闪发光的汽车驶过来，车里走下一位穿着华丽西装的人，他就是脑细胞。自以为是的脑细胞说：“你们都不配当上国王，我做国王才是当之无愧的，如果没有我，人类就会失去智慧，无法正常的生活，也不能创造任何科学技术和发明。”每个人都纷纷说着自己的优点，你一言我一语，吵得面红耳赤，各不相让。只有神经细胞默默地站在一旁，始终一言不发。这时，上皮细胞拍拍桌子，大声说：“你们这些骄傲自满的家伙，只知道好大喜功，自以为是的人怎么能坐上国王的位置，现在只有神经细胞才有资格当国王，他不仅能控制人类的反应、勤勤恳恳地传输信息，而且他从不骄傲，一直保持谦虚的态度，这才是一个国王应该具有的优良品质。”台下的细胞居民们听了，觉得十分有道理，便一致要神经细胞当国王。刚刚吵得最凶的几个细胞，都惭愧地羞红了脸、纷纷地低下了头。从此以后，神经细胞当上了国王，国民们各司其职，安居乐业，过着幸福美满的生活，而小昊每天都是精神满满、神清气爽的。
生命的作文600字这盆嫁接的仙人球是我两年前从花鸟店买回来的。初见它时，它既没有玫瑰的娇嫩艳丽，也没有茉莉的芬芳馥郁。抓住我眼球的是它奇特的形状，亭亭的三棱剑顶着圆圆的仙人球，一朵朵粉红色的小花从密麻麻的刺儿中冒出来，有序地在仙人球的顶部围成一圈儿。它就像是一个戴着花冠的小姑娘，羞答答地藏在繁花绿叶之下。我把这盆仙人球和其它的花一起放在阳台上。花期过后，它显得很不起眼，又长满了刺儿，所以被我移到了角落里。每天浇花时，它总被我落在最后，有时喷水壶里没水了，嫌麻烦就让它干渴着。去年国庆长假，全家人去福州玩了五天。一回到家，我便到阳台上浇花。当看到这盆仙人球时，我吃惊地发现它的三棱剑烂了一个大口子。我把它端出来，盆里的土已干得发白。“呼——呼——”我似乎听到了它缓慢而深沉的呼吸声，听到它无声地乞求：“好渴啊，快浇点水吧！”我给它浇了一大勺水，它“咕咚咕咚”地喝了个饱。我把它当作病号来照料，但是那腐烂的伤口还在扩大，大到我对它能否活下去产生了怀疑。但它以这种残缺的姿态依然顽强地活着。渐渐地，它的伤口结了疤。今年三月初，它居然又开花了。四朵小花依次绽放，默默地诉说着它对春天的渴望。如今，每次看到它，我都倍受震撼：生命可以残缺，但绝不可以放弃！我期待来年春天还能看到那可爱的小花。