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CELLS cell: the basic unit of structure in living things A IM I Wh at are ce lls? The G reat Pyramids Buildings are put together with bricks. Birds buil d their nests with grass and twigs. l verything is made up of smaller Parts. ... EVEN YOU Livia; things are made up of small parts called cells . The cell is the basic unit of structure in all living thing s. Because all living things are made up of cells, cells are ofte n called the building blocks of life." Some organisms, like bacteria, are made up of only one cell. Larger organisms have many more cells. A person, for example, is made up of trillions of cells. Can you imagine how many cells a whale must have? Cells come in many sizes. Most are microscopic )my kruh SKOP ikj. Some cells, however, can be seen easil y. For example, a chicken's egg is a single cell. Do you need a micr oscope to see a chicken's egg? Cells also come in many shapes. For example, a muscle cell has a different shape than a nerve cell. Skin cells have a different shape than fat cells. As you see, there are many differences amo ng cells. But cells also have many things in common. For example, all cells are made up of a living material called prot oplasm (PRO tub plaz urn). Protoplasm is mostly water. But prot oplasm also contains dissolved salts and many organic (car bon) compounds. The term organic means "life.,, A cell is a living thing. It carries out all the life functions. For example, a c ell takes in nutrients and oxygen. It gives off w,wros(e products. Cells use and relea se energy. takes place inside a + Ol?. il nd, cells d1 s o reproduce. Culls are ra2aat"h' 1.11:8 of m any parts. UaCI 'l cel l part has a special job to dJu. 111415s:' part : ork together to keep the cell Inoctioning propi.-rly, im, ycui will learn about sore of these cell parts. You w6'11 also learn how aniral al cells are different from plant (oils. show s seven cell part s . These parts are found name of each cell part is listed below, F igu ell membrane brand l tai (S (ELL %MF tulr pl : r.tx'r:r • rttu"Ieos (NEW klee trs) in almos t every K€xk.irr rxl cell. The m t.cr .hckrt ;tia (rny tub KON dreg rah) n ribosomes (.Y )till soarnkr endoplasm c reticulum (EN deli plaz ra ik rill TIK yoo lu n) • nuclear (NEW klee ar) membrane Each cell part is described below the diagram. As you read each description, n identify the cell part in the diagram, then Figure A A typical animal cell. CE I, IF:MBB RANF A thin covering that surrounds the cell. The cell. membrane a) protects the cell, b) helps give the cell its shape, c) allows materials to enter and leave the cell, and d) helps keep the cell material to gether. NUCLEAR MFMBR A 1E A thin covering that surrounds the nucleus. The nuclear membrane controls the passage of materials into and out of the nucleus. It also gives the nucleus its shape. MI " ONDI UA Mitr::hondria are rod- shaped. They are the "power houses" of the cell. Mitochondria store and release the ener;yT the cell needs to carry out the life functions. ENDOPL%SM IC I lgTICULi..;It A network of channels. The endoplasmic reticulum is like a series of "roadways." They are used for moving materials within the cell. RIBOSOMIES Tiny grainlike structures. The ribosomes make and store protein. Most ribosomes are found on the endoplasmic reticulum. Some, however, move freely within the cytoplasm. Answer the following questions about cells. 8. The parts of the cell that you have labeled are all made up of "living" material, What is the living material of the cell called? 9. Where do most of the life functions take place within a cell? 10. a) b) Does each part of the cell work alone? Explain you answer. WORD ABOUT PLANT CELLS Plant cells and animal cells are similar. But they are not exactly the same. Plant cells have two parts that animal cells do not have. These parts are: a cell wall and chloroplasts. The d: eli w all surrou nds the cell membrane of the pla: c::c 11 wail i s ma de of ;an on iv .i ng Yraat erial gives a plant called ^.iAlulose. The cell its g ^+ f stiffne ss. It helps a plant to st.,ind >C erect. -;laloroplasts are sprea d throughout the cytopl asr ri of plant cells. The cc,hloropfasts contain a green substance called chloro phyll. G reen plants need chlorophyll (along with carbon dioxide and light energy) to make the ir own food. Ghloa•otahy -il is found mostly in leaf ells. Substances must be able to get into and out of a cell in order for the cell to do its job. The passage of these materials takes place thruu 11 boss," controls the passage of these mater membrane has tiny holes. Liquids carrying dissolved substances pass through these holes in it process called osmosis jahs :' IOH sisJ. Osmosis i "chaosr." It allows univ certain substances to move into the ce ll. And only, stances a stay move out of the cell. For example, dissolved nutrients and oxygen can move only into the cell. Dissolved wastes, such as carbon dioxi de, can move only )tit of the cell. What might happen if the amounts of substances entering and leaving the cell were not controlled? It depends.... The cell might a) swell or I. shrink, or c) become poisoned. Think about each of the following possibilities. Write your answer in the space provided. What might happen if: 1. too much liquid moved into a cell? 2. too much liquid moved out of a cell? 3. too little liquid moves into a cell? too 4. much liquid moves out of a cell? 5, b) too little waste moves out of a cell? he letter of he correct Baas What kin liter a) llat a ceii cell needs kinds tit i)Iat +-'r)+ils E k(1d; tii '...!'.ail if ai, O :! F)ee(.ls ,v,as>te :m i.ell,, h) .LS C t sidts erect sizeOsmosis eater cells shape nucleus f(X)'d-IIIakijI8 chloroplasts cell wall life function organn compoun d protoplasm . \ .ir o r 1. The "building blocks" of living things are 2. Cells vary in 3. A cell carries out every 4. The living material of a cell is called Pro and Moser, and Two cell parts that are found only i n plant cells are a 7. Chloroplasts are needed for and in plants. 8. The cell wall helps a plant stand 9. Substances move into and out of a cell through a proce ss called 10. The passage of substances into and out of a cell takes place through the On a separate piece of paper, draw a plc `rc>m rmemory. Be sure to include an d labe iY iYA,r A C.n • mitochondr f ear is reticulun rnembrai WHAT 1S A CELL cell: the basic unit of structure in living things cell membrane: the thin outer covering of a cell nucleus: the part of a cell that controls the cell nuclear membra ne: the thin outer covering of the nucleus cytoplasm : the jelly-like sub- stance inside a cell between the nucleus f. rid the cell membrane protoplasm: a cell the living material of The invention of the microscope made many impo rtant scoveries possible. One of these discoveries was mad e by the ish scientist Robert Hooke in 1665. Hooke disc overed that iving things are made up of even smaller livin g parts. He called these living parts cells. lying things are made up of cells. Some organism s, like large plants and animals, are made up of billions of cells. Others, like bacteria, are made up of only one cell. Cells are living things. All of the life functions are carri ed out by every cell. The cell itself is made up of smaller parts. These parts include the cell membrane [YMEM btane], the nucl eus [Ni81V klee us[, the nuclear [NEW flee ar] membrane, and the cytoplasm [SY toh plat urn]. All of these parts are mad e up of a living substance called protoplasm [PRO tuh plat urn[ . Plant and animal cells are not exactl alike. Plant cells have some parts that animal cells do not have. The se parts are the cell wall and the chloroplasts [KLOR uh plasts]. CELL MEMBRANE The cell membrane is like a thin skin that covers the cell. It protects the cell and gives it its shape. The cell membrane has tiny holes in it. Material s enter and leave the cell through these tiny holes. NUCLEUS The nucleus is inside the cell. It cont rols everything that happens in the cell. The nucleus is like the "boss" of the cell. The nucleus is usually near the cent er of a cell. NUCLEAR MEMBRANE The nuclear membran e surrounds the nucleus. It controls the passage of materials into and out of the nucleus. CYTOPLASM The cytoplasm is a jelly-like subs tance located between the nucleus and the cell membrane. It fills most of the inside of the cell. Like the cell membrane, the cytoplasrn helps give a cell its shape. Most of the life f lrnc- tcjns take Place in the cytoplasm. 44 "D THE PARTS The illustration on the right shows an animal cell. Four parts of this animal cell are shown . `rl ey are: the nucleus, the cell membrane, the nuclear membrane, and the cytoplasm. Find each part of the cell in the picture. Write the nave of each part on the correct line. Are these parts also found in plant cells? PARTS OF AN ANIMAL CELL WHAT Do Look at each picture. T hen answer the questions. THE PICTURES SHOW? The cell membrane has tiny holes in it. Materials needed for the life functions enter the cell through these holes; waste materials leave. 1. 0 , . oxygen and digested food What needed materials enter the cell carbon diox de and other wastes OUT through the cell membrane? t 2. What waste materials leave the cell o cell membrane through the cell membrane? A bird's egg is made up of only one cell. A bird's egg has a hard shell that covers the cell membrane. 3. Do you need a microscope to gee this cell? 4, What extra part does a bird's egg hat most other cells do not have? PECtAL KIND OF C EIJ, 4S ARE PLANT CELLS DII~ F EREN N IMAL C Plant cells and animal cells are not exactly alike. Plant c ells have certain parts that animal culls do not have. These parts include a cell wall and c hioroplasts. • The cell the entire plant cell. outside the cell riser plant cell. It surrounds The cell w all is made of a nonliving material called cellul ose [S E LL yuh loasj. The is more rigid (stiff) than the cell membrane. It gives a plant cell its stiffness, It -es it its shape. n Chloroplasts are found in the cytop lasm of a plant cell. Chloroplasts contain a green substance called chlorophyll {KLOR uh fillJ. Chlorophyll is needed by green plants for food- making, The food-making process of green plants is called photosynthesis [fo tuh SIN thuh sis . Most chlorophyll is found in the leaf cells of green plants. Plants can make their own food. Animals cannot. Anim al cells do not contain chlorophyll. 1. Does photosynthesis take place in animals? 2. Why? MORE ABOUT PLANT CELLS The picture on the right shows a plant cell. The parts of the plant cell that are shown in the picture are listed below. cell membrane nucleus chloroplasts x:ytoplasruu f 1. Find each part of the plant cell in the picture. Write the name of the part on the correct line in the picture. One of the parts has been labeled for you. 'taw, answer the questions about plant cells . 1. What is found inside of the chioroplasts? 2. '}Vhdt is this al used for? Answer the following c and animal culls. ahoc 1. s I . 2. animt7aI c cal ls do not have? _ and Wheat is the cell ",all mad protoplasm, cellulose 3. Is cellulose living material? ties, 110 4. What is the cell membrane made of? 5. Is protoplasm living materi al? 6. Where are the chloroplasts located? protoplasm, c lluInse yes, no in the nucleus, in the cytoplasm 7. Wha t substance is found inside the chloropl asts? protoplasm, chlorophyll S. What is the substance inside the chloroplasts used for? food-making, excretion 9. Can animals make their own food? yes, no 10. Match W hy can' t animals make their own food? the two lists. Write the correct letter on the line next to each number. chlcaroplasts and c ell "v,all i hoto.;v ott(;leus, maclear mein no, ('61 r^i ntnlrrane, ^ f .l^^lli,.ltiflt i'It I, 4(t'i t'. a) parts of all cells h) food-making process of plants c) found only in plant cells d) nnnlivin ,g material of the coil sill e) any living m aterial of the cell :)1PLE TING Complete the sentences with the words below. Three words will SENTENCES be used twice. chlorophyll living chloroplasts rnocleus 1. cell membrane cellulose cytoplasm waste products The parts that all plant and animal cells have are the the 2. life functions cell wall nuclear membrane the , and the A plant cell has two parts that animal cells do not have. They are the and the 3. Cells are every cell. 4. The 5. Materials things. All of the are carried out in is the control center of the cell. needed for the life functions enter the cell throu the 6. leave the cell through the cell membrane. 7. The cell wall of a plant cell is made of a nonliving substance called 8. The special cell parts needed for food-making in plants are the 9. Chloroplasts contain a green substance called WORD Unscramble each of the following to forma word or term that you SCRAMBLE have read in this aim. Write your word in the spaces below. t,CoT`\lYc _SA',fPLOTRO' Look at each picture. Answer the questions next to each pictu What holds up a person? 2. 3. 4. What holds up a plant? -- What is taking place in this picture? In what part of a plant is food made? l' 1 'E' (? ( Write T on the line next to the number if the sentence is true. Write F if the sentence is false. ck has cells. ,Most of a cell is the nucleus. ly the ruckus of it cell is protoplasm. The cell membrane has holes, Most cells sire microscopic in size. t'huit ^_ il "3 , â t;! c2 ,3u mn it t Ods ir(.' t (: it) RE ACC IN(. without looking back, try to draw a picture of an animal cell. Label the nucleus, the nuclear membrane, the cell membrane, and the c°toplasm. 2. Now try to draw a picture of a plant cell. Label the nucleus, the nuclear membrane, the cell membrane, the cell wall, the cytoplasm, and the chloroplasts. s.L'hat do you think would happen i f c vaste products could not leave a cell? t:t